Patent Publication Number: US-2023153960-A1

Title: Merging Split-Pixel Data For Deeper Depth of Field

Description:
BACKGROUND 
     A portion of an image may be blurred due to a corresponding portion of a scene being positioned outside of a depth of field of a camera device capturing the image. The extent of blurring may depend on the position of the corresponding portion of the scene relative to the depth of field, with the amount of blurring increasing as the corresponding portion of the scene moves farther away from the depth of field in either a direction towards the camera or a direction away from the camera. In some cases, image blurring is undesirable, and may be adjusted or corrected using various image processing techniques, models, and/or algorithms. 
     SUMMARY 
     A split-pixel camera may be configured to generate split-pixel image data that includes a plurality of sub-images. For out-of-focus pixels of the split-pixel image data, the frequency content of the sub-images may vary as a function of (i) location of the out-of-focus pixel within the image data and (ii) position of the scene feature represented by the out-of-focus pixel relative to a depth of field of the split-pixel camera (i.e., pixel depth). Specifically, for a given out-of-focus pixel, one of the sub-images may appear sharper than other sub-images, depending on the location and depth associated with the given out-of-focus pixel. Accordingly, the relationship between pixel location, pixel depth, and sub-image frequency content may be characterized for the split-pixel camera, and used to improve the sharpness of portions of the split-pixel image data. In particular, rather than summing, or equally weighting, pixels of the sub-images, sub-image pixels containing both low and high frequency content may be given greater weight than sub-image pixels containing only low frequency content, thereby increasing the apparent sharpness of the resulting image. 
     In a first example embodiment, a method may include obtaining split-pixel image data captured by a split-pixel camera. The split-pixel image data may include a first sub-image and a second sub-image. The method may also include determining, for each respective pixel of a plurality of pixels of the split-pixel image data, a corresponding position of a scene feature represented by the respective pixel relative to a depth of field of the split-pixel camera. The method may additionally include identifying, based on the corresponding position of the scene feature represented by each respective pixel of the plurality of pixels, one or more out-of-focus pixels of the plurality of pixels, where the one or more out-of-focus pixels are positioned outside of the depth of field. The method may further include determining, for each respective out-of-focus pixel of the one or more out-of-focus pixels, a corresponding pixel value based on (i) the corresponding position of the scene feature represented by the respective out-of-focus pixel relative to the depth of field, (ii) a location of the respective out-of-focus pixel within the split-pixel image data, and (iii) at least one of: a first value of a corresponding first pixel in the first sub-image or a second value of a corresponding second pixel in the second sub-image. The method may yet further include generating, based on the corresponding pixel value determined for each respective out-of-focus pixel, an enhanced image having an extended depth of field. 
     In a second example embodiment, a system may include a processor and a non-transitory computer-readable medium having stored thereon instructions that, when executed by the processor, cause the processor to perform operations. The operations may include obtaining split-pixel image data captured by a split-pixel camera. The split-pixel image data may include a first sub-image and a second sub-image. The operations may also include determining, for each respective pixel of a plurality of pixels of the split-pixel image data, a corresponding position of a scene feature represented by the respective pixel relative to a depth of field of the split-pixel camera. The operations may additionally include identifying, based on the corresponding position of the scene feature represented by each respective pixel of the plurality of pixels, one or more out-of-focus pixels of the plurality of pixels, where the one or more out-of-focus pixels are positioned outside of the depth of field. The operations may further include determining, for each respective out-of-focus pixel of the one or more out-of-focus pixels, a corresponding pixel value based on (i) the corresponding position of the scene feature represented by the respective out-of-focus pixel relative to the depth of field, (ii) a location of the respective out-of-focus pixel within the split-pixel image data, and (iii) at least one of: a first value of a corresponding first pixel in the first sub-image or a second value of a corresponding second pixel in the second sub-image. The operations may yet further include generating, based on the corresponding pixel value determined for each respective out-of-focus pixel, an enhanced image having an extended depth of field. 
     In a third example embodiment, a non-transitory computer-readable medium may have stored thereon instructions that, when executed by a computing device, cause the computing device to perform operations. The operations may include obtaining split-pixel image data captured by a split-pixel camera. The split-pixel image data may include a first sub-image and a second sub-image. The operations may also include determining, for each respective pixel of a plurality of pixels of the split-pixel image data, a corresponding position of a scene feature represented by the respective pixel relative to a depth of field of the split-pixel camera. The operations may additionally include identifying, based on the corresponding position of the scene feature represented by each respective pixel of the plurality of pixels, one or more out-of-focus pixels of the plurality of pixels, where the one or more out-of-focus pixels are positioned outside of the depth of field. The operations may further include determining, for each respective out-of-focus pixel of the one or more out-of-focus pixels, a corresponding pixel value based on (i) the corresponding position of the scene feature represented by the respective out-of-focus pixel relative to the depth of field, (ii) a location of the respective out-of-focus pixel within the split-pixel image data, and (iii) at least one of: a first value of a corresponding first pixel in the first sub-image or a second value of a corresponding second pixel in the second sub-image. The operations may yet further include generating, based on the corresponding pixel value determined for each respective out-of-focus pixel, an enhanced image having an extended depth of field. 
     In a fourth example embodiment, a system may include means for obtaining split-pixel image data captured by a split-pixel camera. The split-pixel image data may include a first sub-image and a second sub-image. The system may also include means for determining, for each respective pixel of a plurality of pixels of the split-pixel image data, a corresponding position of a scene feature represented by the respective pixel relative to a depth of field of the split-pixel camera. The system may additionally include means for identifying, based on the corresponding position of the scene feature represented by each respective pixel of the plurality of pixels, one or more out-of-focus pixels of the plurality of pixels, where the one or more out-of-focus pixels are positioned outside of the depth of field. The system may further include means for determining, for each respective out-of-focus pixel of the one or more out-of-focus pixels, a corresponding pixel value based on (i) the corresponding position of the scene feature represented by the respective out-of-focus pixel relative to the depth of field, (ii) a location of the respective out-of-focus pixel within the split-pixel image data, and (iii) at least one of: a first value of a corresponding first pixel in the first sub-image or a second value of a corresponding second pixel in the second sub-image. The system may yet further include means for generating, based on the corresponding pixel value determined for each respective out-of-focus pixel, an enhanced image having an extended depth of field. 
     These, as well as other embodiments, aspects, advantages, and alternatives, will become apparent to those of ordinary skill in the art by reading the following detailed description, with reference where appropriate to the accompanying drawings. Further, this summary and other descriptions and figures provided herein are intended to illustrate embodiments by way of example only and, as such, that numerous variations are possible. For instance, structural elements and process steps can be rearranged, combined, distributed, eliminated, or otherwise changed, while remaining within the scope of the embodiments as claimed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    illustrates a computing device, in accordance with examples described herein. 
         FIG.  2    illustrates a computing system, in accordance with examples described herein. 
         FIG.  3    illustrates a dual-pixel image sensor, in accordance with examples described herein. 
         FIG.  4    illustrates point spread functions associated with split-pixel image data, in accordance with examples described herein. 
         FIG.  5    illustrates a system, in accordance with examples described herein. 
         FIGS.  6 A,  6 B,  6 C,  6 D,  6 E, and  6 F  show pixel sources corresponding to different combinations of pixel depth and pixel location of dual-pixel image data, in accordance with examples described herein. 
         FIG.  6 G  is a table that summarizes the relationships shown in  FIGS.  6 A,  6 B,  6 C,  6 D,  6 E, and  6 F , in accordance with examples described herein. 
         FIGS.  7 A,  7 B,  7 C,  7 D,  7 E, and  7 F  show pixel sources corresponding to different combinations of pixel depth and pixel location of quad-pixel image data, in accordance with examples described herein. 
         FIG.  7 G  is a table that summarizes the relationships shown in  FIGS.  7 A,  7 B,  7 C,  7 D,  7 E, and  7 F , in accordance with examples described herein. 
         FIG.  8    is a flow chart, in accordance with examples described herein. 
     
    
    
     DETAILED DESCRIPTION 
     Example methods, devices, and systems are described herein. It should be understood that the words “example” and “exemplary” are used herein to mean “serving as an example, instance, or illustration.” Any embodiment or feature described herein as being an “example,” “exemplary,” and/or “illustrative” is not necessarily to be construed as preferred or advantageous over other embodiments or features unless stated as such. Thus, other embodiments can be utilized and other changes can be made without departing from the scope of the subject matter presented herein. 
     Accordingly, the example embodiments described herein are not meant to be limiting. It will be readily understood that the aspects of the present disclosure, as generally described herein, and illustrated in the figures, can be arranged, substituted, combined, separated, and designed in a wide variety of different configurations. 
     Further, unless context suggests otherwise, the features illustrated in each of the figures may be used in combination with one another. Thus, the figures should be generally viewed as component aspects of one or more overall embodiments, with the understanding that not all illustrated features are necessary for each embodiment. 
     Additionally, any enumeration of elements, blocks, or steps in this specification or the claims is for purposes of clarity. Thus, such enumeration should not be interpreted to require or imply that these elements, blocks, or steps adhere to a particular arrangement or are carried out in a particular order. Unless otherwise noted, figures are not drawn to scale. 
     I. OVERVIEW 
     A split-pixel camera may be used to generate split-pixel image data that includes two or more sub-images, each generated by a corresponding subset of photosites of the split-pixel camera. For example, the split-pixel camera may include a dual-pixel image sensor with each pixel thereof made up of two photosites. Accordingly, the split-pixel image data may be dual-pixel image data that includes a first sub-image generated by left photosites of the pixels and a second sub-image generated by right photosites of the pixels. In another example, the split-pixel camera may include a quad-pixel image sensor with each pixel thereof made up of four photosites. Accordingly, the split-pixel image data may be quad-pixel image data that includes a first sub-image generated by top left photosites of the pixels, a second sub-image generated by top right photosites of the pixels, a third sub-image generated by bottom left photosites of the pixels, and a fourth sub-image generated by bottom right photosites of the pixels. 
     When a split-pixel camera is used to capture an image of a scene feature (e.g., an object or portion thereof) that is out-of-focus (i.e., positioned outside of a depth of field of the split-pixel camera), the frequency content of the sub-images may differ. Specifically, for each out-of-focus pixel, at least one split-pixel sub-image of the split-pixel image data, referred to as a high frequency pixel source, may represent spatial frequencies above a threshold frequency that are not represented by other split-pixel sub-images of the split-pixel image data, referred to as low frequency pixel source(s). The difference in the frequency content of the sub-images may be a function of (i) a position of the scene feature (e.g., the object or portion thereof) relative to the depth of field (and thus a position, relative to a depth of focus of the camera, of an image representing the scene feature) and (ii) a location (e.g., as represented by coordinates within the image), with respect to an area of the image sensor, of the out-of-focus pixel(s) representing the scene feature. 
     When these two sub-images are summed to generate the split-pixel image, some of the sharpness of the high frequency pixel source may be lost due to the spatial frequencies above the threshold frequency being represented in only one of the sub-images. Accordingly, the sharpness of the overall split-pixel image resulting from combining the sub-images may be enhanced by weighting the high frequency pixel source more heavily than the low frequency pixel source (rather than merely summing the sub-images), resulting in a boosting of the spatial frequencies above the threshold frequency. 
     In some cases, the high frequency pixel source and the low frequency pixel source may be merged in image space. In one example, each out-of-focus pixel may be a weighted sum of the spatially-corresponding pixels in the sub-images, with greater weight being given to the spatially-corresponding high frequency pixel source than the spatially-corresponding low frequency pixel source. In another example, a corresponding source pixel may be selected for each out-of-focus pixel from among the spatially-corresponding pixels of the sub-images. Specifically, the spatially-corresponding high frequency pixel source may be selected as the source pixel, and the spatially-corresponding low frequency pixel source may be discarded. 
     In other cases, the high frequency pixel source and the low frequency pixel source may be merged in frequency space. Specifically, the high frequency pixel source and the low frequency pixel source may each be assigned frequency-specific weights. For example, for frequencies above a threshold frequency, frequencies that are present in the high frequency pixel source, but absent from or underrepresented in the low frequency pixel source, may be boosted to increase the sharpness of the resulting enhanced image. Frequencies below the threshold frequency, and/or frequencies that are present in both the high frequency pixel source and the low frequency pixel source may be weighted equally, thus preserving the content of both sub-images at these frequencies. 
     The difference in the frequency content of the sub-images may be the result of optical imperfections present in the optical path of the split-pixel camera device. Thus, in some cases, the relationship between frequency content, pixel depth, and pixel location may be determined on a per-camera basis and/or a per-camera-model basis, and may subsequently be used in connection with the corresponding camera instance and/or camera model to enhance the sharpness of split-pixel images captured thereby. 
     II. EXAMPLE COMPUTING DEVICES AND SYSTEMS 
       FIG.  1    illustrates an example computing device  100 . Computing device  100  is shown in the form factor of a mobile phone. However, computing device  100  may be alternatively implemented as a laptop computer, a tablet computer, and/or a wearable computing device, among other possibilities. Computing device  100  may include various elements, such as body  102 , display  106 , and buttons  108  and  110 . Computing device  100  may further include one or more cameras, such as front-facing camera  104  and rear-facing camera  112 , one or more of which may be configured to generate dual-pixel image data. 
     Front-facing camera  104  may be positioned on a side of body  102  typically facing a user while in operation (e.g., on the same side as display  106 ). Rear-facing camera  112  may be positioned on a side of body  102  opposite front-facing camera  104 . Referring to the cameras as front and rear facing is arbitrary, and computing device  100  may include multiple cameras positioned on various sides of body  102 . 
     Display  106  could represent a cathode ray tube (CRT) display, a light emitting diode (LED) display, a liquid crystal (LCD) display, a plasma display, an organic light emitting diode (OLED) display, or any other type of display known in the art. In some examples, display  106  may display a digital representation of the current image being captured by front-facing camera  104  and/or rear-facing camera  112 , an image that could be captured by one or more of these cameras, an image that was recently captured by one or more of these cameras, and/or a modified version of one or more of these images. Thus, display  106  may serve as a viewfinder for the cameras. Display  106  may also support touchscreen functions that may be able to adjust the settings and/or configuration of one or more aspects of computing device  100 . 
     Front-facing camera  104  may include an image sensor and associated optical elements such as lenses. Front-facing camera  104  may offer zoom capabilities or could have a fixed focal length. In other examples, interchangeable lenses could be used with front-facing camera  104 . Front-facing camera  104  may have a variable mechanical aperture and a mechanical and/or electronic shutter. Front-facing camera  104  also could be configured to capture still images, video images, or both. Further, front-facing camera  104  could represent, for example, a monoscopic camera. Rear-facing camera  112  may be similarly or differently arranged. Additionally, one or more of front-facing camera  104  and/or rear-facing camera  112  may be an array of one or more cameras. 
     One or more of front-facing camera  104  and/or rear-facing camera  112  may include or be associated with an illumination component that provides a light field to illuminate a target object. For instance, an illumination component could provide flash or constant illumination of the target object. An illumination component could also be configured to provide a light field that includes one or more of structured light, polarized light, and light with specific spectral content. Other types of light fields known and used to recover three-dimensional (3D) models from an object are possible within the context of the examples herein. 
     Computing device  100  may also include an ambient light sensor that may continuously or from time to time determine the ambient brightness of a scene that cameras  104  and/or  112  can capture. In some implementations, the ambient light sensor can be used to adjust the display brightness of display  106 . Additionally, the ambient light sensor may be used to determine an exposure length of one or more of cameras  104  or  112 , or to help in this determination. 
     Computing device  100  could be configured to use display  106  and front-facing camera  104  and/or rear-facing camera  112  to capture images of a target object. The captured images could be a plurality of still images or a video stream. The image capture could be triggered by activating button  108 , pressing a softkey on display  106 , or by some other mechanism. Depending upon the implementation, the images could be captured automatically at a specific time interval, for example, upon pressing button  108 , upon appropriate lighting conditions of the target object, upon moving digital camera device  100  a predetermined distance, or according to a predetermined capture schedule. 
       FIG.  2    is a simplified block diagram showing some of the components of an example computing system  200 . By way of example and without limitation, computing system  200  may be a cellular mobile telephone (e.g., a smartphone), a computer (such as a desktop, notebook, tablet, or handheld computer), a home automation component, a digital video recorder (DVR), a digital television, a remote control, a wearable computing device, a gaming console, a robotic device, a vehicle, or some other type of device. Computing system  200  may represent, for example, aspects of computing device  100 . 
     As shown in  FIG.  2   , computing system  200  may include communication interface  202 , user interface  204 , processor  206 , data storage  208 , and camera components  224 , all of which may be communicatively linked together by a system bus, network, or other connection mechanism  210 . Computing system  200  may be equipped with at least some image capture and/or image processing capabilities. It should be understood that computing system  200  may represent a physical image processing system, a particular physical hardware platform on which an image sensing and/or processing application operates in software, or other combinations of hardware and software that are configured to carry out image capture and/or processing functions. 
     Communication interface  202  may allow computing system  200  to communicate, using analog or digital modulation, with other devices, access networks, and/or transport networks. Thus, communication interface  202  may facilitate circuit-switched and/or packet-switched communication, such as plain old telephone service (POTS) communication and/or Internet protocol (IP) or other packetized communication. For instance, communication interface  202  may include a chipset and antenna arranged for wireless communication with a radio access network or an access point. Also, communication interface  202  may take the form of or include a wireline interface, such as an Ethernet, Universal Serial Bus (USB), or High-Definition Multimedia Interface (HDMI) port. Communication interface  202  may also take the form of or include a wireless interface, such as a Wi-Fi, BLUETOOTH®, global positioning system (GPS), or wide-area wireless interface (e.g., WiMAX or 3GPP Long-Term Evolution (LTE)). However, other forms of physical layer interfaces and other types of standard or proprietary communication protocols may be used over communication interface  202 . Furthermore, communication interface  202  may comprise multiple physical communication interfaces (e.g., a Wi-Fi interface, a BLUETOOTH® interface, and a wide-area wireless interface). 
     User interface  204  may function to allow computing system  200  to interact with a human or non-human user, such as to receive input from a user and to provide output to the user. Thus, user interface  204  may include input components such as a keypad, keyboard, touch-sensitive panel, computer mouse, trackball, joystick, microphone, and so on. User interface  204  may also include one or more output components such as a display screen which, for example, may be combined with a touch-sensitive panel. The display screen may be based on CRT, LCD, and/or LED technologies, or other technologies now known or later developed. User interface  204  may also be configured to generate audible output(s), via a speaker, speaker jack, audio output port, audio output device, earphones, and/or other similar devices. User interface  204  may also be configured to receive and/or capture audible utterance(s), noise(s), and/or signal(s) by way of a microphone and/or other similar devices. 
     In some examples, user interface  204  may include a display that serves as a viewfinder for still camera and/or video camera functions supported by computing system  200 . Additionally, user interface  204  may include one or more buttons, switches, knobs, and/or dials that facilitate the configuration and focusing of a camera function and the capturing of images. It may be possible that some or all of these buttons, switches, knobs, and/or dials are implemented by way of a touch-sensitive panel. 
     Processor  206  may comprise one or more general purpose processors—e.g., microprocessors—and/or one or more special purpose processors—e.g., digital signal processors (DSPs), graphics processing units (GPUs), floating point units (FPUs), network processors, or application-specific integrated circuits (ASICs). In some instances, special purpose processors may be capable of image processing, image alignment, and merging images, among other possibilities. Data storage  208  may include one or more volatile and/or non-volatile storage components, such as magnetic, optical, flash, or organic storage, and may be integrated in whole or in part with processor  206 . Data storage  208  may include removable and/or non-removable components. 
     Processor  206  may be capable of executing program instructions  218  (e.g., compiled or non-compiled program logic and/or machine code) stored in data storage  208  to carry out the various functions described herein. Therefore, data storage  208  may include a non-transitory computer-readable medium, having stored thereon program instructions that, upon execution by computing system  200 , cause computing system  200  to carry out any of the methods, processes, or operations disclosed in this specification and/or the accompanying drawings. The execution of program instructions  218  by processor  206  may result in processor  206  using data  212 . 
     By way of example, program instructions  218  may include an operating system  222  (e.g., an operating system kernel, device driver(s), and/or other modules) and one or more application programs  220  (e.g., camera functions, address book, email, web browsing, social networking, audio-to-text functions, text translation functions, and/or gaming applications) installed on computing system  200 . Similarly, data  212  may include operating system data  216  and application data  214 . Operating system data  216  may be accessible primarily to operating system  222 , and application data  214  may be accessible primarily to one or more of application programs  220 . Application data  214  may be arranged in a file system that is visible to or hidden from a user of computing system  200 . 
     Application programs  220  may communicate with operating system  222  through one or more application programming interfaces (APIs). These APIs may facilitate, for instance, application programs  220  reading and/or writing application data  214 , transmitting or receiving information via communication interface  202 , receiving and/or displaying information on user interface  204 , and so on. 
     In some cases, application programs  220  may be referred to as “apps” for short. Additionally, application programs  220  may be downloadable to computing system  200  through one or more online application stores or application markets. However, application programs can also be installed on computing system  200  in other ways, such as via a web browser or through a physical interface (e.g., a USB port) on computing system  200 . 
     Camera components  224  may include, but are not limited to, an aperture, shutter, recording surface (e.g., photographic film and/or an image sensor), lens, shutter button, infrared projectors, and/or visible-light projectors. Camera components  224  may include components configured for capturing of images in the visible-light spectrum (e.g., electromagnetic radiation having a wavelength of 380-700 nanometers) and components configured for capturing of images in the infrared light spectrum (e.g., electromagnetic radiation having a wavelength of 701 nanometers-1 millimeter). Camera components  224  may be controlled at least in part by software executed by processor  206 . 
     III. EXAMPLE DUAL-PIXEL IMAGE SENSOR 
       FIG.  3    illustrates a split-pixel image sensor  300  that is configured to generate split-pixel image data. Specifically, split-pixel image sensor  300  is shown as a dual-pixel image sensor that includes a plurality of pixels arranged in a grid that includes columns  302 ,  304 ,  306 , and  308  through  310  (i.e., columns  302 - 310 ) and rows  312 ,  314 ,  316 , and  318  through  320  (i.e., rows  312 - 320 ). Each pixel is shown divided into a first (e.g., left) photosite, indicated with a corresponding hatched region, and a second (e.g., right) photosite, indicated with a corresponding white-filled region. Thus, the right half of the pixel located at column  302 , row  312  is labeled “R” to indicate the right photosite, and the left half of the pixel is labeled “L” to indicate the left photosite. 
     Although the photosites of each pixel are shown dividing each pixel into two equal vertical halves, the photosites may alternatively divide each pixel in other ways. For example, each pixel may be divided into a top photosite and a bottom photosite. The areas of the photosites might not be equal. Further, while split-pixel image sensor  300  is shown as a dual-pixel image sensor that includes two photosites per pixel, split-pixel image sensor  300  may alternatively be implemented with each pixel divided into a different number of photosites. For example, split-pixel image sensor  300  may be implemented as a quad-pixel image sensor with each respective pixel thereof divided into four photosites that define four quadrants of the respective pixel (e.g., a (first) top left quadrant, a (second) top right quadrant, a (third) bottom left quadrant, and a (fourth) bottom right quadrant). 
     Each photosite of a given pixel may include a corresponding photodiode, the output signal of which may be read independently of other photodiodes. Additionally, each pixel of split-pixel image sensor  300  may be associated with a corresponding color filter (e.g., red, green, or blue). A demosaicing algorithm may be applied to the output of split-pixel image sensor  300  to generate a color image. In some cases, fewer than all of the pixels of split-pixel image sensor  300  may be divided into multiple photosites. For example, each pixel associated with a green color filter may be divided into two independent photosites, while each pixel associated with a red or blue color filter may include a single photosite. In some cases split-pixel image sensor  300  may be used to implement front-facing camera  104  and/or rear-facing camera  112 , and may form part of camera components  224 . 
     Split-pixel image sensor  300  may be configured to generate split-pixel image data. In one example, the split-pixel image data may be dual-pixel image data that includes a first sub-image generated by a first set of photosites (e.g., left photosites only) and a second sub-image generated by a second set of photosites (e.g., right photosites only). In another example, the split-pixel image data may be quad-pixel image data that includes a first sub-image generated by a first set of photosites (e.g., top left photosites only), a second sub-image generated by a second set of photosites (e.g., top right photosites only), a third sub-image generated by a third set of photosites (e.g., bottom left photosites only), and a fourth sub-image generated by a fourth set of photosites (e.g., bottom right photosites only). 
     The sub-images may be generated as part of a single exposure. For example, the sub-images may be captured substantially simultaneously, with a capture time of one sub-image being within a threshold time of a capture time of another sub-image. The signals generated by each photosite of a given pixel may be combined into a single output signal, thereby generating conventional (e.g., RGB) image data. 
     When a scene feature, such as a foreground object, a background object, an environment, and/or portion(s) thereof, being imaged is in-focus (i.e., the scene feature is within a depth of field of the camera, and/or light reflected therefrom is focused within a depth of focus of the camera), the respective signal generated by each photosite of a given pixel may be substantially the same (e.g., the signals of a split-pixel may be within a threshold of one another). When the scene feature being imaged is out-of-focus (i.e., the scene feature is in front of or behind the depth of field of the camera, and/or the light reflected therefrom is focused in front of or behind the depth of focus of the camera), the respective signal generated by a first photosite of a given pixel may differ from the respective signal(s) generated by the other photosite(s) of the given pixel. The extent of this difference may be proportional to an extent of defocus, and may indicate the position of the scene feature relative to the depth of field (and the position at which light reflected therefrom is focused relative to the depth of focus). Accordingly, split-pixel image data may be used to determine whether a scene feature being photographed is within, in front of, and/or behind a depth of field of the camera device. 
     IV. EXAMPLE POINT SPREAD FUNCTIONS OF SPLIT-PIXEL IMAGE DATA 
       FIG.  4    illustrates an example spatial variation of point spread functions (PSFs) of a dual-pixel image sensor (e.g., split-pixel image sensor  300 ) associated with imaging an out-of-focus plane. Specifically,  FIG.  4    shows regions  400 ,  402 , and  404 , each corresponding to an area of the dual-pixel image sensor. PSFs in region  402  show the spatial variation of PSFs associated with a left sub-image, PSFs in region  404  shows the spatial variation of PSFs associated with a right sub-image, and PSFs in region  400  represents the spatial variation of PSFs associated with the overall dual-pixel image, each while imaging the out-of-focus plane. As indicated in  FIG.  4   , the PSFs of the overall dual-pixel image are equal to a sum of the PSFs of the left sub-image and the right sub-image. The size scale of the PSFs in relation to the size of the dual-pixel image sensor was chosen for clarity of illustration, and may be different in various implementations. 
     Each respective region of regions  400 ,  402 , and  404  includes sixteen PSFs arranged into rows  410 ,  412 ,  414 , and  416  and columns  420 ,  422 ,  424 , and  426 . Additionally, a corresponding dashed line shows a vertical midline of each respective region, and thus divides the respective region into two equal halves: a left half and a right half. The left half of region  402  includes PSFs that allow for capture of a greater extent of spatial high-frequency information than PSFs of the right half of region  402 , as indicated by the differences in the shading pattern of these PSFs. Specifically, the PSFs in columns  420  and  422  of region  402  have a higher cut-off spatial frequency than the PSFs in columns  424  and  426  of region  402 . Similarly, the right half of region  404  includes PSFs that allow for capture of a greater extent of spatial high-frequency information than PSFs of the left half of region  404 , as indicated by the differences in the shading pattern of these PSFs. Specifically, the PSFs in columns  424  and  426  of region  404  have a higher cut-off spatial frequency than the PSFs in columns  420  and  422  of region  404 . 
     Accordingly, when imaging an out-of-focus region of a scene, the left half of the first sub-image corresponding to region  402  may appear sharper than (i) the right half of the first sub-image and (ii) the left half of the second sub-image corresponding to region  404 . Similarly, when imaging the out-of-focus region of the scene, the right half of the second sub-image corresponding to region  404  appears sharper than (i) the left half of the second sub-image and (ii) the right half of the first sub-image corresponding to region  402 . 
     This spatial variability of frequency content across split-pixel sub-images may be a result of various real-world imperfections in the optical path of the dual-pixel camera device, and might not be apparent from idealized optics models. In some cases, the spatial variability may be empirically characterized on a per-camera-model basis, and subsequently used to generate enhanced versions of images captured by that camera model. 
     When the first sub-image and the second sub-image are added, the resulting overall dual-pixel image corresponds to region  400 . That is, the resulting dual-pixel image appears to have been generated using a dual-pixel image sensor associated with the PSFs of region  400 . Accordingly, the relatively sharper content of the left half of the first sub-image (corresponding to region  402 ) is combined with, and thus blurred by, the content of the left half of the second sub-image (corresponding to region  404 ). Similarly, the relatively sharper content of the right half of the second sub-image (corresponding to region  404 ) is combined with, and thus blurred by, the content of the right half of the first sub-image (corresponding to region  402 ). 
     Specifically, frequencies up to a first cut-off frequency of the PSFs in the right half of region  402  and/or the left half of region  404  are represented in both halves of each of regions  402  and  404 . However, frequencies between (i) the first cut-off frequency and (ii) a second cut-off frequency of the PSFs in the left half of region  402  and/or the right half of region  404  are represented in the left half of region  402  and the right half of region  404 , but not in the right half of region  402  and the left half of region  404 . Accordingly, when the PSFs of region  402  and  404  are added to form the PSFs of region  400 , the frequencies between the first cut-off frequency and the second cut-off frequency are underrepresented (e.g., their relative power is lower) as compared with frequencies below the first cut-off frequency. Thus, summing pixel values of the sub-images does not take advantage of the differences in spatial frequency content present at different portions of the sub-images. 
     The PSFs in  FIG.  4    correspond to an out-of-focus plane positioned on a first side of the focus plane and/or depth of field (e.g., between (i) the camera device and (ii) the focus plane and/or depth of field). When the out-of-focus plane is instead positioned on a second side of the focus plane (e.g., beyond the focus plane), the pattern of PSFs shown in  FIG.  4    may be different. For example, the pattern of PSFs may be flipped, and may be approximated by the PSFs of region  402  and region  404  switching places. A corresponding PSF variation may additionally or alternatively be observed when each split-pixel is instead divided into a top photosite and a bottom photosite, and/or into four photosites that divide the split-pixel into four quadrants, among other possibilities. The relationship between PSF cut-off frequencies across the area of the image sensor and scene feature position relative to the depth of field may vary among camera models, and may thus be empirically determined on a per-camera-model basis. 
     V. EXAMPLE SYSTEM FOR GENERATING ENHANCED IMAGES 
     The presence of high-frequency spatial information in different parts of the split-pixel sub-images may be used to enhance split-pixel images by improving the sharpness of the split-pixel images, and thus effectively extending the corresponding depth of field. Specifically,  FIG.  5    illustrates an example system for generating enhanced images by taking advantage of high-frequency information present in some parts of split-pixel sub-images.  FIG.  5    illustrates system  500  configured to generate enhanced image  528  based on split-pixel image data  502 . System  500  may include pixel depth calculator  508 , pixel depth classifier  512 , pixel frequency classifier  520 , and pixel value merger  526 . The components of system  500  may be implemented as hardware, software, or a combination thereof. 
     Split-pixel image data  502  may include sub-image  504  through sub-image  506  (i.e., sub-images  504 - 506 ). Split-pixel image data  502  may be captured by split-pixel image sensor  300 . Each sub-image of sub-images  504 - 506  may have the same resolution as split-pixel image data  502 , and may be captured as part of a single exposure. Accordingly, each respective pixel of split-pixel image data  502  may be associated with a corresponding pixel in each of sub-images  504 - 506 . In one example, split-pixel image data  502  may include two sub-images, and may thus be referred to as dual-pixel image data. In another example, split-pixel image data  502  may include four sub-images, and may thus be referred to as quad-pixel image data. 
     When split-pixel image data  502  represents scene features that are positioned outside of the depth of field of the split-pixel camera (resulting in corresponding light being focused outside of the depth of focus of the split-pixel camera), some of sub-images  504 - 506  may include high-frequency spatial information that might not be present in other ones of sub-images  504 - 506 . The term “high-frequency” and/or variations thereof are used herein to refer to frequencies above a threshold frequency, where a first split-pixel sub-image contains frequency content above the threshold frequency while a corresponding second split-pixel sub-image does not. Conversely, the term “low-frequency” and/or variations thereof are used herein to refer to frequencies below and including the threshold frequency. The threshold frequency may vary depending on the split-pixel camera and/or the scene being photographed, among other factors. 
     Pixel depth calculator  508  may be configured to determine pixel depth(s)  510  for a plurality of pixels of split-pixel image data  502 . For example, pixel depth(s)  510  may correspond to all of the pixels of split-pixel image data  502 , or less than all of the pixels of split-pixel image data  502 . Pixel depth(s)  510  may indicate the depth of corresponding scene feature(s) (e.g., objects and/or portions thereof) relative to the depth of field of the split-pixel camera, and/or the depth of corresponding images of the scene feature(s) relative to the depth of focus of the split-pixel camera. In some implementations, pixel depth(s)  510  may include a binary representation of, for example, the depth associated with the corresponding scene feature, indicating whether the corresponding scene feature is positioned behind (e.g., on a first side) the depth of field of the split-pixel camera or in front (e.g., on a second side) of the depth of field of the split-pixel camera. In some cases, pixel depth(s) may include a ternary representation that is additionally configured to indicate that, for example, the corresponding scene feature is positioned and/or focused within the depth of field of the split-pixel camera. 
     In other implementations, pixel depth(s)  510  may take on more than three values, and may thus indicate, for example, how far in front of the depth of field and/or how far behind the depth of field the corresponding scene feature is positioned. It is to be understood that when a scene feature is positioned outside of the depth of field (i.e., the region in front of the lens, scene features within which will produce images that appear sufficiently focused) of a split-pixel camera, a corresponding image (i.e., light representing the corresponding scene feature) is also positioned (i.e., focused) outside of a depth of field (i.e., the region behind the lens within which images appear sufficiently focused) of the split-pixel camera. 
     Pixel depth calculator  508  may be configured to determine the depth value of a respective pixel based on the signal disparity between (i) a corresponding first pixel in a first sub-image of sub-images  504 - 506  and (ii) a corresponding second pixel in a second sub-image of sub-images  504 - 506 . Specifically, the signal disparity may be positive when scene features are positioned on a first side of the depth of field, and may be negative when scene features are positioned on a second side of the depth of field. Thus, the sign of the disparity may indicate the direction, relative to the depth of field, of the depth value of the respective pixel, while the magnitude of the disparity may indicate the magnitude of the depth value. In the case of quad-pixel image data, the depth value may additionally or alternatively be based on a corresponding third pixel in a third sub-image of sub-images  504 - 506  and a corresponding fourth pixel in a fourth sub-image of sub-images  504 - 506 . 
     Pixel depth classifier  512  may be configured to identify, based on pixel depth(s)  510 , (i) in-focus pixel(s)  514  of split-pixel image data  502  and (ii) out-of-focus pixel(s)  516  of split-pixel image data  502 . In-focus pixel(s)  514  may represent scene features that are positioned within the depth of field (e.g., within a threshold distance on either side of a focus plane), and thus might not undergo a depth of field and/or sharpness enhancement. Out-of-focus pixel(s)  516  may represent scene features that are positioned outside of the depth of field (e.g., outside of the threshold distance on either side of a focus plane), and thus may undergo a depth of field and/or sharpness enhancement. Each respective out-of-focus pixel of out-of-focus pixel(s)  516  may be associated with a corresponding pixel location of pixel location(s)  518 , where the corresponding pixel location indicates, for example, the coordinates of the respective out-of-focus pixel within split-pixel image data  502 . Each respective out-of-focus pixel may also be associated with a corresponding pixel depth of pixel depth(s)  510 . 
     Pixel frequency classifier  520  may be configured to identify, for each respective out-of-focus pixel of out-of-focus pixel(s)  516 , high frequency pixel source(s)  522  and low frequency pixel source(s)  524 . Specifically, pixel frequency classifier  520  may be configured to identify high frequency pixel source(s)  522  and low frequency pixel source(s)  524  based on the location of the respective pixel within split-pixel image data  502  and the depth value associated with the respective pixel. High frequency pixel source(s)  522  for the respective out-of-focus pixel may include locationally-corresponding pixels(s) of a first subset of sub-images  504 - 506 , while low frequency pixel source(s)  524  for the respective out-of-focus pixel may include locationally-corresponding pixels(s) of a second subset of sub-images  504 - 506 . The first subset and the second subset determined for the respective pixel may be mutually exclusive. 
     In the case of dual-pixel image data, high frequency pixel source(s)  522  may indicate, for example, that sub-image  504  contains sharper (i.e., higher frequency) image content for the respective pixel and low frequency pixel source(s)  524  may indicate that sub-image  506  contains less sharp (i.e., lower frequency) image content for the respective pixel. In the case of quad-pixel image data, high frequency pixel source(s)  522  may indicate, for example, that sub-image  506  contains sharper image content for the respective pixel and low frequency pixel source(s)  524  may indicate that all other sub-images, including sub-image  504 , contain less sharp image content for the respective pixel. Pixel source selection is illustrated in and discussed in more detail with respect to  FIGS.  6 A- 7 G . 
     Pixel value merger  526  may be configured to generate enhanced image  528  based on (i) in-focus pixel(s)  514  and (ii) high frequency pixel source(s)  522  and low frequency pixel source(s)  524  determined for each respective out-of-focus pixel of out-of-focus pixel(s)  516 . Specifically, pixel value merger  526  may be configured to generate respective pixel values for in-focus pixel(s)  514  by summing the spatially-corresponding pixel values of sub-images  504 - 506 . For out-of-focus pixel(s)  516 , pixel value merger  526  may be configured to generate respective pixel values by giving greater weight to high frequency pixel source(s)  522  than to low frequency pixel source(s)  524  (at least with respect to some frequencies) to thereby increase the apparent sharpness and/or depth of field of the corresponding parts of split-pixel image data  502 . 
     VI. EXAMPLE RELATIONSHIPS BETWEEN PIXEL DEPTH, PIXEL LOCATION, AND SUB-IMAGE FREQUENCY CONTENT 
       FIGS.  6 A- 6 F  illustrate example mappings between locations of respective pixels within dual-pixel image data, depth values associated with the respective pixels, and sub-images that contain high frequency image contents. Specifically, each of  FIGS.  6 A- 6 F  shows, on the left side, an area of the dual-pixel image divided into four quadrants labeled with a corresponding depth and, on the right side, corresponding sub-image quadrants that, given the corresponding depth, provide high frequency content for each of the quadrants of the dual-pixel image. 
     A quadrant of an image may be a rectangular region spanning one fourth of an image frame and resulting from horizontal and vertical bisection of the image frame. Thus, four quadrants may span the entirety of the image frame and divide the image frame into four equal subsections. Similarly, a half of the image may be a union of two adjacent quadrants. For example, the union of two horizontally-adjacent quadrants may define a top half or a bottom half, and the union of two vertically-adjacent quadrants may define a left half or a right half. Stated another way, a top half and a bottom half of the image may be defined by a horizontal bisection of the image into two equal rectangular regions, while a left half and a right half of the image may be defined by a vertical bisection of the image into two equal rectangular regions. The overall split-pixel image (e.g., image data  502 ), the sub-images (e.g., sub-images  504 - 506 ), and/or the enhanced image (e.g., enhanced image  528 ) may each be divided into corresponding halves and/or quadrants. 
       FIG.  6 A  shows that when quadrants  600 ,  602 ,  604 , and  606  of the dual-pixel image sensor are each used to image a plane (i.e., a scene having a constant depth relative to the split-pixel camera) that is positioned on a first side (e.g., behind) of the depth of field, as indicated by DEPTH: −1, then: (i) quadrant  610  of the first dual-pixel sub-image contains higher frequency content for quadrant  600  than correspondingly-located quadrant  620  of the second dual-pixel sub-image, (ii) quadrant  622  of the second sub-image contains higher frequency content for quadrant  602  than correspondingly-located quadrant  612  of the first sub-image, (iii) quadrant  614  of the first sub-image contains higher frequency content for quadrant  604  than correspondingly-located quadrant  624  of the second sub-image, and (iv) quadrant  626  of the second sub-image contains higher frequency content for quadrant  606  than correspondingly-located quadrant  616  of the first sub-image. 
       FIG.  6 B  shows that when quadrants  600 ,  602 ,  604 , and  606  of the dual-pixel image sensor are each used to image a plane that is positioned on a second side (e.g., in front) of the depth of field, as indicated by DEPTH: +1, then: (i) quadrant  620  of the second sub-image contains higher frequency content for quadrant  600  than correspondingly-located quadrant  610  of the first sub-image, (ii) quadrant  612  of the first sub-image contains higher frequency content for quadrant  602  than correspondingly-located quadrant  622  of the second sub-image, (iii) quadrant  624  of the second sub-image contains higher frequency content for quadrant  604  than correspondingly-located quadrant  614  of the first sub-image, (iv) quadrant  616  of the first sub-image contains higher frequency content for quadrant  606  than correspondingly-located quadrant  626  of the second sub-image. 
       FIG.  6 C  shows that when quadrants  600  and  604  are each used to image a plane that is positioned on the first side of the depth of field, as indicated by DEPTH: −1, and quadrants  602  and  606  are each used to image a plane that is positioned on the second side of the depth of field, as indicated by DEPTH: +1, then quadrants  610 ,  612 ,  614 , and  616  of the first sub-image contains higher frequency content for quadrants  600 ,  602 ,  604 , and  606 , respectively, than quadrants  620 ,  622 ,  624 , and  626 , respectively, of the second sub-image. 
       FIG.  6 D  shows that when quadrants  600  and  604  are each used to image a plane that is positioned on the second side of the depth of field, as indicated by DEPTH: +1, and quadrants  602  and  606  are each used to image a plane that is positioned on the first side of the depth of field, as indicated by DEPTH: −1, then quadrants  620 ,  622 ,  624 , and  626  of the second sub-image contains higher frequency content for quadrants  600 ,  602 ,  604 , and  606 , respectively, than quadrants  610 ,  612 ,  614 , and  616 , respectively, of the first sub-image. 
       FIG.  6 E  shows that when quadrants  600  and  602  are each used to image a plane that is positioned on the second side of the depth of field, as indicated by DEPTH: +1, and quadrants  604  and  606  are each used to image a plane that is positioned on the first side of the depth of field, as indicated by DEPTH: −1, then: (i) quadrants  612  and  614  of the first sub-image contain higher frequency content for quadrants  602  and  604 , respectively, than quadrants  622  and  624 , respectively, of the second sub-image and (ii) quadrants  620  and  626  of the second sub-image contain higher frequency content for quadrants  600  and  606 , respectively, than quadrants  610  and  616 , respectively, of the first sub-image. 
       FIG.  6 F  shows that when quadrants  600  and  602  are each used to image a plane that is positioned on the first side of the depth of field, as indicated by DEPTH: −1, and quadrants  604  and  606  are each used to image a plane that is positioned on the second side of the depth of field, as indicated by DEPTH: +1, then: (i) quadrants  610  and  616  of the first sub-image contain higher frequency content for quadrants  600  and  606 , respectively, than quadrants  620  and  626 , respectively, of the second sub-image and (ii) quadrants  622  and  624  of the second sub-image contain higher frequency content for quadrants  602  and  604 , respectively, than quadrants  612  and  614 , respectively, of the first sub-image. 
       FIG.  6 G  shows table  630  that summarizes the relationships illustrated by the example pixel location and pixel depth combinations of  FIGS.  6 A- 6 F . Specifically, when the scene feature is positioned within the depth of field (i.e., Scene Depth=0), the frequency content of the first sub-image is substantially and/or approximately the same as the frequency content of the second sub-image (e.g., per-frequency signal power differs by no more than a threshold amount). Thus, the pixel values of in-focus pixels may be obtained by adding the values of corresponding pixels in the first sub-image and the second sub-image, without applying unequal weighing to these values to improve sharpness. 
     When the scene feature is positioned on the first side of the depth of field (i.e., Scene Depth=−1), the first (e.g., left) sub-image provides higher frequency content for out-of-focus pixels located in the first (e.g., left) half (e.g. quadrants  600  and  604 ) of the dual-pixel image, and the second (e.g., right) sub-image provides higher frequency content for out-of-focus pixels located in the second (e.g., right) half (e.g. quadrants  602  and  606 ) of the dual-pixel image. When the scene feature is positioned on the second side of the depth of field (i.e., Scene Depth=+1), the second sub-image provides higher frequency content for out-of-focus pixels located in the first half of the dual-pixel image, and the first sub-image provides higher frequency content for out-of-focus pixels located in the second half of the dual-pixel image. 
       FIGS.  7 A- 7 F  illustrate example mappings between locations of respective pixels within quad-pixel image data, depth values associated with the respective pixels, and sub-images that contain high frequency image contents. Specifically, each of  FIGS.  7 A- 7 F  shows, on the left side, an area of the quad-pixel image divided into quadrants labeled with a corresponding depth and, on the right side, sub-image quadrants that provide high frequency content for each of the quadrants of the quad-pixel image given the corresponding depth. 
       FIG.  7 A  shows that when quadrants  700 ,  702 ,  704 , and  706  of the quad-pixel image sensor are each used to image a plane that is positioned on the first side of the depth of field, as indicated by DEPTH: −1, then: (i) quadrant  710  of the first quad-pixel sub-image contains higher frequency content for quadrant  700  than corresponding quadrants of the three other quad-pixel sub-images (e.g., correspondingly-located quadrant  740  of the fourth quad-pixel sub-image), (ii) quadrant  722  of the second quad-pixel sub-image contains higher frequency content for quadrant  702  than corresponding quadrants of the three other quad-pixel sub-images (e.g., correspondingly-located quadrant  732  of the third quad-pixel sub-image), (iii) quadrant  734  of the third quad-pixel sub-image contains higher frequency content for quadrant  704  than corresponding quadrants of the three other quad-pixel sub-images (e.g., correspondingly-located quadrant  724  of the second quad-pixel sub-image), and (iv) quadrant  746  of the fourth quad-pixel sub-image contains higher frequency content for quadrant  706  than corresponding quadrants of the three other quad-pixel sub-images (e.g., correspondingly-located quadrant  716  of the first quad-pixel sub-image). 
       FIG.  7 B  shows that when quadrants  700 ,  702 ,  704 , and  706  of the quad-pixel image sensor are each used to image a plane that is positioned on the second side of the depth of field, as indicated by DEPTH: +1, then: (i) quadrant  740  of the fourth sub-image contains higher frequency content for quadrant  700  than corresponding quadrants of the three other sub-images (e.g., correspondingly-located quadrant  710  of the first sub-image), (ii) quadrant  732  of the third sub-image contains higher frequency content for quadrant  702  than corresponding quadrants of the three other sub-images (e.g., correspondingly-located quadrant  722  of the second sub-image), (iii) quadrant  724  of the second sub-image contains higher frequency content for quadrant  704  than corresponding quadrants of the three other sub-images (e.g., correspondingly-located quadrant  734  of the third sub-image), and (iv) quadrant  716  of the first sub-image contains higher frequency content for quadrant  706  than corresponding quadrants of the three other sub-images (e.g., correspondingly-located quadrant  746  of the fourth sub-image). 
       FIG.  7 C  shows that when quadrants  700  and  704  are each used to image a plane that is positioned on the first side of the depth of field, as indicated by DEPTH: −1, and quadrants  702  and  706  are each used to image a plane that is positioned on the second side of the depth of field, as indicated by DEPTH: +1, then: (i) quadrants  710  and  716  of the first sub-image contain higher frequency content for quadrants  700  and  706 , respectively, than corresponding quadrants of the three other sub-images (e.g., quadrants  740  and  746 , respectively, of the fourth sub-image) and (ii) quadrants  732  and  734  of the third sub-image contain higher frequency content for quadrants  702  and  704 , respectively, than corresponding quadrants of the three other sub-images (e.g., quadrants  722  and  724 , respectively, of the second sub-image). 
       FIG.  7 D  shows that when quadrants  700  and  704  are each used to image a plane that is positioned on the second side of the depth of field, as indicated by DEPTH: +1, and quadrants  702  and  706  are each used to image a plane that is positioned on the first side of the depth of field, as indicated by DEPTH: −1, then: (i) quadrants  740  and  746  of the fourth sub-image contain higher frequency content for quadrants  700  and  706 , respectively, than corresponding quadrants of the three other sub-images (e.g., quadrants  710  and  716 , respectively, of the first sub-image) and (ii) quadrants  722  and  724  of the second sub-image contain higher frequency content for quadrants  702  and  704 , respectively, than corresponding quadrants of the three other sub-images (e.g., quadrants  732  and  734 , respectively, of the third sub-image). 
       FIG.  7 E  shows that when quadrants  700  and  702  are each used to image a plane that is positioned on the second side of the depth of field, as indicated by DEPTH: +1, and quadrants  704  and  706  are each used to image a plane that is positioned on the first side of the depth of field, as indicated by DEPTH: −1, then: (i) quadrants  740  and  746  of the fourth sub-image contain higher frequency content for quadrants  700  and  706 , respectively, than corresponding quadrants of the three other sub-images (e.g., quadrants  710  and  716 , respectively, of the first sub-image) and (ii) quadrants  732  and  734  of the third sub-image contain higher frequency content for quadrants  702  and  704 , respectively, than corresponding quadrants of the three other sub-images (e.g., quadrants  722  and  724 , respectively, of the second sub-image). 
       FIG.  7 F  shows that when quadrants  700  and  702  are each used to image a plane that is positioned on the first side of the depth of field, as indicated by DEPTH: −1, and quadrants  704  and  706  are each used to image a plane that is positioned on the second side of the depth of field, as indicated by DEPTH: +1, then: (i) quadrants  710  and  716  of the first sub-image contain higher frequency content for quadrants  700  and  706 , respectively, than corresponding quadrants of the three other sub-images (e.g., quadrants  740  and  746 , respectively, of the fourth sub-image) and (ii) quadrants  722  and  724  of the third sub-image contain higher frequency content for quadrants  702  and  704 , respectively, than corresponding quadrants of the three other sub-images (e.g., quadrants  732  and  734 , respectively, of the third sub-image). 
       FIG.  7 G  shows table  750  that summarizes the relationship illustrated by the example pixel location and pixel depth combinations of  FIGS.  7 A- 7 F . Specifically, when the scene feature is positioned within the depth of field (i.e., Scene Depth=0), the frequency contents of the first sub-image, the second sub-image, the third sub-image, and the fourth sub-image are substantially and/or approximately the same. Thus, the pixel values of in-focus pixels may be obtained by adding the values of corresponding pixels in the first through fourth sub-images, without applying unequal weighing to these values to improve sharpness. 
     When the scene feature is positioned on the first side of the depth of field (i.e., Scene Depth=−1), the first sub-image provides higher frequency content for out-of-focus pixels located in the first quadrant (e.g., quadrant  700 ) of the quad-pixel image, the second sub-image provides higher frequency content for out-of-focus pixels located in the second quadrant (e.g., quadrant  702 ) of the quad-pixel image, the third sub-image provides higher frequency content for out-of-focus pixels located in the third quadrant (e.g., quadrant  704 ) of the quad-pixel image, and the fourth sub-image provides higher frequency content for out-of-focus pixels located in the fourth quadrant (e.g., quadrant  706 ) of the quad-pixel image. 
     When the scene feature is positioned on the second side of the depth of field (i.e., Scene Depth=+1), the fourth sub-image provides higher frequency content for out-of-focus pixels located in the first quadrant (e.g., quadrant  700 ) of the dual-pixel image, the third sub-image provides higher frequency content for out-of-focus pixels located in the second quadrant (e.g., quadrant  702 ) of the dual-pixel image, the second sub-image provides higher frequency content for out-of-focus pixels located in the third quadrant (e.g., quadrant  704 ) of the dual-pixel image, and the first sub-image provides higher frequency content for out-of-focus pixels located in the fourth quadrant (e.g., quadrant  706 ) of the dual-pixel image. 
     While  FIGS.  6 A- 6 G and  7 A — 7 G illustrate the relationships between pixel location, pixel depth, and high frequency data source on a per-quadrant level (for clarity of illustration), in practice, the determination of the high frequency pixel source may be made on a per-pixel level (based on per-pixel locations and per-pixel depths). Thus, a particular pixel&#39;s high frequency source may be determined using the relationships shown in  FIGS.  6 A- 6 G and/or  7 A- 7 G  based on (i) the particular pixel&#39;s corresponding depth and (ii) the half (in the case of dual-pixel images) or quadrant (in the case of quad-pixel images) of the split-pixel image in which the particular pixel is located. Accordingly, although  FIGS.  6 A- 6 F and  7 A — 7 F show particular arrangements of pixel depths for the purpose of illustration of the relationships shown in  FIGS.  6 G and  7 G , respectively, different distributions and/or combinations of pixel depth may be observed in practice. The relationships shown in  FIGS.  6 G and  7 G  may be used to identify, for each pixel in the split-pixel image, a corresponding sub-image that contains high frequency information that may be absent from the other split-pixel images. 
     VII. EXAMPLE PIXEL VALUE MERGING 
     Turning back to  FIG.  5   , pixel value merger  526  may be configured to combine the corresponding pixel values of high frequency pixel source(s)  522  and low frequency pixel source(s)  524  in a plurality of ways. In particular, for out-of-focus pixel(s)  516 , pixel value merger  526  may be configured to favor, or give greater weight to, high frequency pixel source(s)  522  than to low frequency pixel source(s)  524 . In some cases, greater weight may be given to high frequency pixel source(s)  522  than to low frequency pixel source(s)  524  with respect to all frequencies. In other cases, greater weight may be given to high frequency pixel source(s)  522  than to low frequency pixel source(s)  524  with respect to frequencies above a threshold frequency (e.g., cut-off frequency separating the frequency content of different sub-images), and while equal weight may be given to frequencies below or equal to the threshold frequency. 
     In one example, the combination of pixel values may be performed in the spatial domain. A given pixel of enhanced image  528  corresponding to an out-of-focus pixel of split-pixel image data  502  (i.e., where D i,j ∉Depth of Field (DOF)) may be expressed as P i,j   ENHANCED =w 1 (i,j,D i,j )P i,j   1 + . . . +w N (i,j,D i,j )P i,j   N , where P i,j  represents the pixel value at pixel location (i.e., coordinates) i,j of a given image, P ENHANCED  represents enhanced image  528 , P 1  represents sub-image  504 , P N  represents sub-image  506 , D i,j  represents the depth value associated with the pixel at pixel location i,j, and w 1 (i,j,D i,j ) through w N (i,j,D i,j ) are weighting functions configured to favor the corresponding high frequency pixel source(s)  522  over the low frequency pixel source(s)  524 . In some cases, for each respective pixel location (i,j), the sum of weights may be normalized to a predetermined value, such as N (e.g., Σ M=1   N  w M (i,j,D i,j )=N). A given pixel of enhanced image  528  corresponding to an in-focus pixel of split-pixel image data  502  (i.e., where D i,j ∈DOF) may be expressed as P i,j   ENHANCED =P i,j   1 + . . . + P i,j   N , where (i,j,D i,j )= . . . =w N (i,j,D i,j )=1. 
     In one example, in the case of dual-pixel image data, 
     
       
         
           
             
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     when P 1  is the high frequency pixel source (and P 2  is thus the low frequency pixel source) for pixel location i,j. That is, for a given out-of-focus pixel of split-pixel image data  502 , the pixel value from the high frequency pixel source may be weighted more heavily than (i.e., assigned a weight greater than) the pixel value from the low frequency pixel source in order to sharpen the given out-of-focus pixel. In another example, in the case of dual-pixel image data, P i,j   ENHANCED =2P i,j   1 +(0)P i,j   2 =2P i,j   1  when P 1  is the high frequency pixel source (and P 2  is thus the low frequency pixel source) for pixel location i,j. That is, for a given out-of-focus pixel of split-pixel image data  502 , the high frequency pixel source may be selected as the exclusive source of the pixel value, and the low frequency pixel source may be discarded. 
     The weighting functions w i (i,j,D i,j ) through w N (i,j,D i,j ) may be discrete or continuous functions of D i,j . The weighting functions w 1 (i,j,D i,j ) through w N (i,j,D i,j ) may be a linear function of D i,j  or may be an exponential function of D i,j , among other possibilities. The weight assigned to a particular high frequency pixel source by its corresponding weighting function may result in the high frequency pixel source making up between (i) 50% of the signal of the corresponding pixel in enhanced image  528  (e.g., when D i,j ∈DOF) and (ii) 100% of the signal of the corresponding pixel in enhanced image  528  (e.g., when |D i,j |&gt;D THRESHOLD ). 
     In another example, the combination of pixel values may be performed in the frequency domain. For example, a given pixel of enhanced image  528  corresponding to an out-of-focus pixel of split-pixel image data  502  (i.e., where D i,j  E DOF) may be expressed as P i,j   ENHANCED =IFT(F ENHANCED (ω))=IFT(v 1 (ω,i,j,D i,j )F 1 (ω)+ . . . +v N (ω,i,j,D i,j )F N (ω)), where ω=(ω x ,ω y ) represents the horizontal spatial frequencies and vertical spatial frequencies, respectively, that may be present in a split-pixel image data  502 , F ENHANCED  represents enhanced image  528  in the frequency domain, F 1 (ω) represents sub-image  504  in the frequency domain, F N (ω) represents sub-image  506  in the frequency domain, D i,j  represents the depth value associated with the pixel at coordinate i,j, IFT( ) represents an inverse frequency transform (e.g., Inverse Fourier Transform, Inverse Cosine Transform, etc.), and v 1 (ω,i,j,D i,j ) through v N (ω,i,j,D i,j ) are frequency-specific weighting functions configured to boost high frequencies that are present in the corresponding high frequency pixel source(s)  522  relative to the low frequencies present in both the corresponding high frequency pixel source(s)  522  and the corresponding low frequency pixel source(s)  524 . In some cases, for each respective spatial frequency ω of a given pixel, the sum of weights may be normalized to a predetermined value, such as N (e.g., Σ M=1   N v M (ω,i,j,D i,j )=N). A given pixel of enhanced image  528  corresponding to an in-focus pixel of split-pixel image data  502  (i.e., where D i,j ∈DOF) may be expressed as P i,j   ENHANCED =IFT(F 1 (ω)+ . . . +F N (ω)), where v 1 (ω,i,j,D i,j )= . . . =v N  (ω,i,j,D i,j )=1. 
     In some implementations, the weighting functions v 1 (ω,i,j,D i,j ) through v N (ω,i,j,D i,j ) may additionally or alternatively be a function of differences in frequency content among the sub-images. For example, for spatial frequencies above a threshold frequency (i.e., ∀ω&gt;ω THRESHOLD ), a high frequency pixel source may be weighted more heavily than a low frequency pixel source when the difference between these sources exceeds a threshold difference, and the two pixel sources may be weighted equally if the difference between these sources is below or equal to the threshold difference. For spatial frequencies below or equal to the threshold frequency (i.e., ∀ω≤ω THRESHOLD ), the high frequency pixel source and the low frequency pixel source may be weighted equally. 
     Thus, in the context of dual-pixel image data, ∀ω&gt;ω THRESHOLD , W 1 (ω,i,j,D i,j )&gt;W 2 (ω,i,j,D i,j ) when F 1 (ω)−F 2 (ω)&gt;F THRESHOLD  (with F 1 (ω) being the high frequency pixel source), W 2 (ω,i,j,D i,j )&gt;W 1 (ω,i,j,D i,j ) when F 2 (ω)−F 1 (ω)&gt;F THRESHOLD  (with F 2  (ω) being the high frequency pixel source), and W 1 (ω,i,j,D i,j )=W 2 (ω,i,j,D i,j ) when |F 1 (ω)−F 2 (ω)|≤F THRESHOLD . ∀ω≤ω THRESHOLD  W 1 (ω,i,j,D i,j )=W 2 (ω,i,j,D i,j ). 
     The threshold frequency may be based on (e.g., equal to) the cut-off frequency of the low frequency pixel source. The threshold difference may be based on (e.g., greater than twice the average or peak of) noise levels expected to be present in the sub-images at different frequencies. Thus, for out-of-focus pixels, high frequency contents of the high frequency pixel source(s)  522  (which are absent from the low frequency pixel source) may be boosted to sharpen the split-pixel image, while low frequency contents present in both pixel sources  522  and  524  may be equally weighted to preserve the contents of both sources at these frequencies. 
     The weighting functions v 1 (ω,i,j,D i,j ) through v N (ω,i,j,D i,j ) may be discrete or continuous functions of D i,j , and/or may be linear or exponential functions of D i,j , among other possibilities. The weight assigned, by its corresponding weighting function, to a particular frequency present in high frequency pixel source may result in the high frequency pixel source making up between (i) 50% of the frequency-specific signal of the corresponding pixel in enhanced image  528  (e.g., when D i,j ∈DOF and/or when ω≤ω THRESHOLD ) and (ii) 100% of the frequency-specific signal of the corresponding pixel in enhanced image  528  (e.g., when |D i,j |&gt;D THRESHOLD  and/or when ω&gt;ω THRESHOLD ). 
     In another example, the combination of pixel values may be performed using one or more algorithms configured to merge an image focus stack. Specifically, an image focus stack may include a plurality of images, with each image captured at a corresponding different focus (resulting in a different position of the depth of focus and/or the depth of field). Thus, different images of the image focus stack may include differing in-focus portions and out-of-focus portions. Algorithms configured to merge an image focus stack may involve, for example, (i) computing per-pixel weights based on the pixel&#39;s contrast and using the per-pixel weights to combine the images of the focus stack, (ii) determining a depth map for each image in the focus stack and using the depth maps to identify the sharpest pixel values in the focus stack, and/or (iii) using a pyramid-based approach to identify the sharpest pixels, among other possibilities. 
     In the context of non-split-pixel image data, the image focus stack may include motion blur due to different images in the image focus stack being captured at different times. Thus, reconstruction of an image with enhanced sharpness may be difficult for scenes that include motion. 
     In the context of split-pixel image data, the plurality of sub-images of the split-pixel image data may be used to form the image focus stack. Variation in the spatial frequency content of the sub-images in out-of-focus regions of split-pixel image data may approximate different focus levels (and thus different depth of focus and depth of field positions). Since the spatial frequency content variation of the sub-images may be achieved without explicit adjustment of the focal distance of the split-pixel camera, the split-pixel sub-images may be captured as part of a single exposure, and thus might not include motion blur (or may at least include less motion blur than a comparable non-split-pixel image focus stack). Accordingly, split-pixel sub-images may be merged using one or more focus stacking algorithms, and thus used to generate enhanced images for static and/or dynamic scenes. 
     VIII. ADDITIONAL EXAMPLE OPERATIONS 
       FIG.  8    illustrates a flow chart of operations related to generation of images with an enhanced sharpness and/or depth of field. The operations may be carried out by computing device  100 , computing system  200 , and/or system  500 , among other possibilities. The embodiments of  FIG.  8    may be simplified by the removal of any one or more of the features shown therein. Further, these embodiments may be combined with features, aspects, and/or implementations of any of the previous figures or otherwise described herein. 
     Block  800  may involve obtaining split-pixel image data captured by a split-pixel camera, wherein the split-pixel image data comprises a first sub-image and a second sub-image. 
     Block  802  may involve determining, for each respective pixel of a plurality of pixels of the split-pixel image data, a corresponding position of a scene feature represented by the respective pixel relative to a depth of field of the split-pixel camera. 
     Block  804  may involve identifying, based on the corresponding position of the scene feature represented by each respective pixel of the plurality of pixels, one or more out-of-focus pixels of the plurality of pixels, wherein the one or more out-of-focus pixels are positioned outside of the depth of field. 
     Block  806  may involve determining, for each respective out-of-focus pixel of the one or more out-of-focus pixels, a corresponding pixel value based on (i) the corresponding position of the scene feature represented by the respective out-of-focus pixel relative to the depth of field, (ii) a location of the respective out-of-focus pixel within the split-pixel image data, and (iii) at least one of: a first value of a corresponding first pixel in the first sub-image or a second value of a corresponding second pixel in the second sub-image. 
     Block  808  may involve generating, based on the corresponding pixel value determined for each respective out-of-focus pixel, an enhanced image having an extended depth of field. 
     In some embodiments, determining the corresponding pixel value may include selecting, for each respective out-of-focus pixel, one of: the corresponding first pixel or the corresponding second pixel, as a source pixel for the respective out-of-focus pixel based on (i) the corresponding position of the scene feature represented by the respective out-of-focus pixel relative to the depth of field and (ii) the location of the respective out-of-focus pixel within the split-pixel image data. The corresponding pixel value may be determined for each respective out-of-focus pixel based on a value of the source pixel. 
     In some embodiments, for out-of-focus pixels located in a first half of the split-pixel image data: the corresponding first pixel may be selected as the source pixel when the scene feature represented by the respective out-of-focus pixel is positioned behind the depth of field, and the corresponding second pixel may be selected as the source pixel when the scene feature represented by the respective out-of-focus pixel is positioned in front of the depth of field. For out-of-focus pixels located in a second half of the split-pixel image data: the corresponding second pixel may be selected as the source pixel when the scene feature represented by the respective out-of-focus pixel is positioned behind the depth of field, and the corresponding first pixel may be selected as the source pixel when the scene feature represented by the respective out-of-focus pixel is positioned in front of the depth of field. 
     In some embodiments, selecting the source pixel for the respective out-of-focus pixel may include, for out-of-focus pixels located in a first half of the split-pixel image data, determining whether the scene feature represented by the respective out-of-focus pixel is positioned behind the depth of field or in front of the depth of field. Selecting the source pixel for the respective out-of-focus pixel may also include, for out-of-focus pixels located in the first half of the split-pixel image data, based on and/or in response to determining that the scene feature represented by the respective out-of-focus pixel is positioned behind the depth of field, selecting the corresponding first pixel as the source pixel, or based on and/or in response to determining that the scene feature represented by the respective out-of-focus pixel is positioned in front of the depth of field, selecting the corresponding second pixel as the source pixel. 
     Selecting the source pixel for the respective out-of-focus pixel may additionally include, for out-of-focus pixels located in a second half of the split-pixel image data, determining whether the scene feature represented by the respective out-of-focus pixel is positioned behind the depth of field or in front of the depth of field. Selecting the source pixel for the respective out-of-focus pixel may further include, for out-of-focus pixels located in the second half of the split-pixel image data, based on and/or in response to determining that the scene feature represented by the respective out-of-focus pixel is positioned behind the depth of field, selecting the corresponding second pixel as the source pixel, or based on and/or in response to determining that the scene feature represented by the respective out-of-focus pixel is positioned in front of the depth of field, selecting the corresponding first pixel as the source pixel. 
     In some embodiments, determining the corresponding pixel value may include determining, for each respective out-of-focus pixel, a first weight for the corresponding first pixel and a second weight for the corresponding second pixel based on (i) the corresponding position of the scene feature represented by the respective out-of-focus pixel relative to the depth of field and (ii) the location of the respective out-of-focus pixel within the split-pixel image data. The corresponding pixel value may be determined for each respective out-of-focus pixel based on (i) a first product of the first weight and the first value of the corresponding first pixel and (ii) a second product of the second weight and the second value of the corresponding second pixel. 
     In some embodiments, for out-of-focus pixels located in a first half of the split-pixel image data: the first weight for the corresponding first pixel may be greater than the second weight for the corresponding second pixel when the scene feature represented by the respective out-of-focus pixel is positioned behind the depth of field, and the second weight for the corresponding second pixel may be greater than the first weight for the corresponding first pixel when the scene feature represented by the respective out-of-focus pixel is positioned in front of the depth of field. For out-of-focus pixels located in a second half of the split-pixel image data: the second weight for the corresponding second pixel may be greater than the first weight for the corresponding first pixel when the scene feature represented by the respective out-of-focus pixel is positioned behind the depth of field, and the first weight for the corresponding first pixel may be greater than the second weight for the corresponding second pixel when the scene feature represented by the respective out-of-focus pixel is positioned in front of the depth of field. 
     In some embodiments, determining the first weight and the second weight may include, for out-of-focus pixels located in a first half of the split-pixel image data, determining whether the scene feature represented by the respective out-of-focus pixel is positioned behind the depth of field or in front of the depth of field. Determining the first weight and the second weight may also include, for out-of-focus pixels located in the first half of the split-pixel image data, based on and/or in response to determining that the scene feature represented by the respective out-of-focus pixel is positioned behind the depth of field, determining the first weight that is greater than the second weight, or based on and/or in response to determining that the scene feature represented by the respective out-of-focus pixel is positioned in front of the depth of field, determining the second weight that is greater than the first weight. 
     Determining the first weight and the second weight may additionally include, for out-of-focus pixels located in a second half of the split-pixel image data, determining whether the scene feature represented by the respective out-of-focus pixel is positioned behind the depth of field or in front of the depth of field. Determining the first weight and the second weight may further include, for out-of-focus pixels located in the second half of the split-pixel image data, based on and/or in response to determining that the scene feature represented by the respective out-of-focus pixel is positioned behind the depth of field, determining the second weight that is greater than the first weight, or based on and/or in response to determining that the scene feature represented by the respective out-of-focus pixel is positioned in front of the depth of field, determining the first weight that is greater than the second weight. 
     In some embodiments, determining the first weight and the second weight may include determining, for each respective spatial frequency of a plurality of spatial frequencies present within the split-pixel image data, (i) a first magnitude of the respective spatial frequency within the first sub-image and (ii) a second magnitude of the respective spatial frequency within the second sub-image. A difference between the first magnitude and the second magnitude may be determined for each respective spatial frequency. The first weight for the first magnitude and the second weight for the second magnitude may be determined for each respective spatial frequency. For each respective spatial frequency above a threshold frequency and associated with a difference that exceeds a threshold value, the first weight may differ from the second weight, and the first weight and the second weight may be based on the corresponding position of the scene feature represented by the respective out-of-focus pixel relative to the depth of field. For each respective spatial frequency (i) below the threshold frequency or (ii) above the threshold frequency and associated with a difference that does not exceed the threshold value, the first weight may be equal to the second weight. The corresponding pixel value may be determined for each respective out-of-focus pixel based on a sum of (i) a first plurality of products of the first weight and the first magnitude for each respective spatial frequency represented by the first value of the corresponding first pixel and (ii) a second plurality of products of the second weight and the second magnitude for each respective spatial frequency represented by the second value of the corresponding second pixel. 
     In some embodiments, the split-pixel image data may include the first sub-image, the second sub-image, a third sub-image, and a fourth sub-image. Determining the corresponding pixel value may include selecting, for each respective out-of-focus pixel, one of: the corresponding first pixel in the first sub-image, the corresponding second pixel in the second sub-image, a corresponding third pixel in the third sub-image, or a corresponding fourth pixel in the fourth sub-image, as a source pixel for the respective out-of-focus pixel based on (i) the corresponding position of the scene feature represented by the respective out-of-focus pixel relative to the depth of field and (ii) the location of the respective out-of-focus pixel within the split-pixel image data. The corresponding pixel value may be determined for each respective out-of-focus pixel based on a value of the source pixel. 
     In some embodiments, for out-of-focus pixels located in a first quadrant of the split-pixel image data: the corresponding first pixel may be selected as the source pixel when the scene feature represented by the respective out-of-focus pixel is positioned behind the depth of field, and the corresponding fourth pixel may be selected as the source pixel when the scene feature represented by the respective out-of-focus pixel is positioned in front of the depth of field. For out-of-focus pixels located in a second quadrant of the split-pixel image data: the corresponding second pixel may be selected as the source pixel when the scene feature represented by the respective out-of-focus pixel is positioned behind the depth of field, and the corresponding third pixel may be selected as the source pixel when the scene feature represented by the respective out-of-focus pixel is positioned in front of the depth of field. For out-of-focus pixels located in a third quadrant of the split-pixel image data: the corresponding third pixel may be selected as the source pixel when the scene feature represented by the respective out-of-focus pixel is positioned behind the depth of field, and the corresponding second pixel may be selected as the source pixel when the scene feature represented by the respective out-of-focus pixel is positioned in front of the depth of field. For out-of-focus pixels located in a fourth quadrant of the split-pixel image data: the corresponding fourth pixel may be selected as the source pixel when the scene feature represented by the respective out-of-focus pixel is positioned behind the depth of field, and the corresponding first pixel may be selected as the source pixel when the scene feature represented by the respective out-of-focus pixel is positioned in front of the depth of field. 
     In some embodiments, selecting the source pixel for the respective out-of-focus pixel may include, for out-of-focus pixels located in a first quadrant of the split-pixel image data, determining whether the scene feature represented by the respective out-of-focus pixel is positioned behind the depth of field or in front of the depth of field. Selecting the source pixel for the respective out-of-focus pixel may also include, for out-of-focus pixels located in the first quadrant of the split-pixel image data, based on and/or in response to determining that the scene feature represented by the respective out-of-focus pixel is positioned behind the depth of field, selecting the corresponding first pixel as the source pixel, or based on and/or in response to determining that the scene feature represented by the respective out-of-focus pixel is positioned in front of the depth of field, selecting the corresponding fourth pixel as the source pixel. 
     Selecting the source pixel for the respective out-of-focus pixel may additionally include, for out-of-focus pixels located in a second quadrant of the split-pixel image data, determining whether the scene feature represented by the respective out-of-focus pixel is positioned behind the depth of field or in front of the depth of field. Selecting the source pixel for the respective out-of-focus pixel may further include, for out-of-focus pixels located in the second quadrant of the split-pixel image data, based on and/or in response to determining that the scene feature represented by the respective out-of-focus pixel is positioned behind the depth of field, selecting the corresponding second pixel as the source pixel, or based on and/or in response to determining that the scene feature represented by the respective out-of-focus pixel is positioned in front of the depth of field, selecting the corresponding third pixel as the source pixel. 
     Selecting the source pixel for the respective out-of-focus pixel may additionally include, for out-of-focus pixels located in a third quadrant of the split-pixel image data, determining whether the scene feature represented by the respective out-of-focus pixel is positioned behind the depth of field or in front of the depth of field. Selecting the source pixel for the respective out-of-focus pixel may further include, for out-of-focus pixels located in the third quadrant of the split-pixel image data, based on and/or in response to determining that the scene feature represented by the respective out-of-focus pixel is positioned behind the depth of field, selecting the corresponding third pixel as the source pixel, or based on and/or in response to determining that the scene feature represented by the respective out-of-focus pixel is positioned in front of the depth of field, selecting the corresponding second pixel as the source pixel. 
     Selecting the source pixel for the respective out-of-focus pixel may additionally include, for out-of-focus pixels located in a fourth quadrant of the split-pixel image data, determining whether the scene feature represented by the respective out-of-focus pixel is positioned behind the depth of field or in front of the depth of field. Selecting the source pixel for the respective out-of-focus pixel may further include, for out-of-focus pixels located in the fourth quadrant of the split-pixel image data, based on and/or in response to determining that the scene feature represented by the respective out-of-focus pixel is positioned behind the depth of field, selecting the corresponding fourth pixel as the source pixel, or based on and/or in response to determining that the scene feature represented by the respective out-of-focus pixel is positioned in front of the depth of field, selecting the corresponding first pixel as the source pixel. 
     In some embodiments, the split-pixel image data may include the first sub-image, the second sub-image, a third sub-image, and a fourth sub-image. Determining the corresponding pixel value may include determining, for each respective out-of-focus pixel, a first weight for the corresponding first pixel, a second weight for the corresponding second pixel, a third weight for a corresponding third pixel in the third sub-image, and a fourth weight for a corresponding fourth pixel in the fourth sub-image based on (i) the corresponding position of the scene feature represented by the respective out-of-focus pixel relative to the depth of field and (ii) the location of the respective out-of-focus pixel within the split-pixel image data. The corresponding pixel value may be determined for each respective out-of-focus pixel based on (i) a first product of the first weight and the first value of the corresponding first pixel, (ii) a second product of the second weight and the second value of the corresponding second pixel, (iii) a third product of the third weight and a third value of the corresponding third pixel, and (ii) a fourth product of the fourth weight and a fourth value of the corresponding fourth pixel. 
     In some embodiments, for out-of-focus pixels located in a first quadrant of the split-pixel image data: the first weight for the corresponding first pixel may be greater than the second weight for the corresponding second pixel, the third weight for the corresponding third pixel, and the fourth weight for the corresponding fourth pixel when the scene feature represented by the respective out-of-focus pixel is positioned behind the depth of field, and the fourth weight for the corresponding fourth pixel may be greater than the first weight for the corresponding first pixel, the second weight for the corresponding second pixel, and the third weight for the corresponding third pixel when the scene feature represented by the respective out-of-focus pixel is positioned in front of the depth of field. For out-of-focus pixels located in a second quadrant of the split-pixel image data: the second weight for the corresponding second pixel may be greater than the first weight for the corresponding first pixel, the third weight for the corresponding third pixel, and the fourth weight for the corresponding fourth pixel when the scene feature represented by the respective out-of-focus pixel is positioned behind the depth of field, and the third weight for the corresponding third pixel may be greater than the first weight for the corresponding first pixel, the second weight for the corresponding second pixel, and the fourth weight for the corresponding fourth pixel when the scene feature represented by the respective out-of-focus pixel is positioned in front of the depth of field. For out-of-focus pixels located in a third quadrant of the split-pixel image data: the third weight for the corresponding third pixel may be greater than the first weight for the corresponding first pixel, the second weight for the corresponding second pixel, and the fourth weight for the corresponding fourth pixel when the scene feature represented by the respective out-of-focus pixel is positioned behind the depth of field, and the second weight for the corresponding second pixel may be greater than the first weight for the corresponding first pixel, the third weight for the corresponding third pixel, and the fourth weight for the corresponding fourth pixel when the scene feature represented by the respective out-of-focus pixel is positioned in front of the depth of field. For out-of-focus pixels located in a fourth quadrant of the split-pixel image data: the fourth weight for the corresponding fourth pixel may be greater than the first weight for the corresponding first pixel, the second weight for the corresponding second pixel, and the third weight for the corresponding third pixel when the scene feature represented by the respective out-of-focus pixel is positioned behind the depth of field, and the first weight for the corresponding first pixel may be greater than the second weight for the corresponding second pixel, the third weight for the corresponding third pixel, and the fourth weight for the corresponding fourth pixel when the scene feature represented by the respective out-of-focus pixel is positioned in front of the depth of field. 
     In some embodiments, determining the first weight, the second weight, the third weight, and the fourth weight may include, for out-of-focus pixels located in a first quadrant of the split-pixel image data, determining whether the scene feature represented by the respective out-of-focus pixel is positioned behind the depth of field or in front of the depth of field. Determining the first weight, the second weight, the third weight, and the fourth weight may also include, for out-of-focus pixels located in the first quadrant of the split-pixel image data, based on and/or in response to determining that the scene feature represented by the respective out-of-focus pixel is positioned behind the depth of field, determining the first weight that is greater than the second weight, the third weight, and the fourth weight, or based on and/or in response to determining that the scene feature represented by the respective out-of-focus pixel is positioned in front of the depth of field, determining the fourth weight that is greater than the first weight, the second weight, and the third weight. 
     Determining the first weight, the second weight, the third weight, and the fourth weight may additionally include, for out-of-focus pixels located in a second quadrant of the split-pixel image data, determining whether the scene feature represented by the respective out-of-focus pixel is positioned behind the depth of field or in front of the depth of field. Determining the first weight, the second weight, the third weight, and the fourth weight may further include, for out-of-focus pixels located in the second quadrant of the split-pixel image data, based on and/or in response to determining that the scene feature represented by the respective out-of-focus pixel is positioned behind the depth of field, determining the second weight that is greater than the first weight, the third weight, and the fourth weight, or based on and/or in response to determining that the scene feature represented by the respective out-of-focus pixel is positioned in front of the depth of field, determining the third weight that is greater than the first weight, the second weight, and the fourth weight. 
     Determining the first weight, the second weight, the third weight, and the fourth weight may additionally include, for out-of-focus pixels located in a third quadrant of the split-pixel image data, determining whether the scene feature represented by the respective out-of-focus pixel is positioned behind the depth of field or in front of the depth of field. Determining the first weight, the second weight, the third weight, and the fourth weight may further include, for out-of-focus pixels located in the third quadrant of the split-pixel image data, based on and/or in response to determining that the scene feature represented by the respective out-of-focus pixel is positioned behind the depth of field, determining the third weight that is greater than the first weight, the second weight, and the fourth weight, or based on and/or in response to determining that the scene feature represented by the respective out-of-focus pixel is positioned in front of the depth of field, determining the second weight that is greater than the first weight, the third weight, and the fourth weight. 
     Determining the first weight, the second weight, the third weight, and the fourth weight may additionally include, for out-of-focus pixels located in a fourth quadrant of the split-pixel image data, determining whether the scene feature represented by the respective out-of-focus pixel is positioned behind the depth of field or in front of the depth of field. Determining the first weight, the second weight, the third weight, and the fourth weight may further include, for out-of-focus pixels located in the fourth quadrant of the split-pixel image data, based on and/or in response to determining that the scene feature represented by the respective out-of-focus pixel is positioned behind the depth of field, determining the fourth weight that is greater than the first weight, the second weight, and the third weight, or based on and/or in response to determining that the scene feature represented by the respective out-of-focus pixel is positioned in front of the depth of field, determining the first weight that is greater than the second weight, the third weight, and the fourth weight. 
     In some embodiments, respective sub-images of the split-pixel image data may have been captured as part of a single exposure by corresponding photosites of the split-pixel camera. 
     In some embodiments, based on the corresponding position of the scene feature represented by each respective pixel of the plurality of pixels, one or more in-focus pixels of the plurality of pixels may be identified. Scene features represented by the one or more in-focus pixels may be positioned within the depth of field. For each respective in-focus pixel of the one or more in-focus pixels, a corresponding pixel value may be determined by adding the first value of the corresponding first pixel in the first sub-image and the second value of the corresponding second pixel in the second sub-image. The enhanced image may be generated further based on the corresponding pixel value determined for each respective in-focus pixel. 
     In some embodiments, determining the corresponding position of the scene feature represented by the respective pixel relative to the depth of field of the split-pixel camera may include determining, for each respective pixel of the plurality of pixels of the split-pixel image data, a difference between the corresponding first pixel in the first sub-image and the corresponding second pixel in the second sub-image, and determining, for each respective pixel of the plurality of pixels of the split-pixel image data, the corresponding position based on the difference. 
     IX. CONCLUSION 
     The present disclosure is not to be limited in terms of the particular embodiments described in this application, which are intended as illustrations of various aspects. Many modifications and variations can be made without departing from its scope, as will be apparent to those skilled in the art. Functionally equivalent methods and apparatuses within the scope of the disclosure, in addition to those described herein, will be apparent to those skilled in the art from the foregoing descriptions. Such modifications and variations are intended to fall within the scope of the appended claims. 
     The above detailed description describes various features and operations of the disclosed systems, devices, and methods with reference to the accompanying figures. In the figures, similar symbols typically identify similar components, unless context dictates otherwise. The example embodiments described herein and in the figures are not meant to be limiting. Other embodiments can be utilized, and other changes can be made, without departing from the scope of the subject matter presented herein. It will be readily understood that the aspects of the present disclosure, as generally described herein, and illustrated in the figures, can be arranged, substituted, combined, separated, and designed in a wide variety of different configurations. 
     With respect to any or all of the message flow diagrams, scenarios, and flow charts in the figures and as discussed herein, each step, block, and/or communication can represent a processing of information and/or a transmission of information in accordance with example embodiments. Alternative embodiments are included within the scope of these example embodiments. In these alternative embodiments, for example, operations described as steps, blocks, transmissions, communications, requests, responses, and/or messages can be executed out of order from that shown or discussed, including substantially concurrently or in reverse order, depending on the functionality involved. Further, more or fewer blocks and/or operations can be used with any of the message flow diagrams, scenarios, and flow charts discussed herein, and these message flow diagrams, scenarios, and flow charts can be combined with one another, in part or in whole. 
     A step or block that represents a processing of information may correspond to circuitry that can be configured to perform the specific logical functions of a herein-described method or technique. Alternatively or additionally, a block that represents a processing of information may correspond to a module, a segment, or a portion of program code (including related data). The program code may include one or more instructions executable by a processor for implementing specific logical operations or actions in the method or technique. The program code and/or related data may be stored on any type of computer readable medium such as a storage device including random access memory (RAM), a disk drive, a solid state drive, or another storage medium. 
     The computer readable medium may also include non-transitory computer readable media such as computer readable media that store data for short periods of time like register memory, processor cache, and RAM. The computer readable media may also include non-transitory computer readable media that store program code and/or data for longer periods of time. Thus, the computer readable media may include secondary or persistent long term storage, like read only memory (ROM), optical or magnetic disks, solid state drives, compact-disc read only memory (CD-ROM), for example. The computer readable media may also be any other volatile or non-volatile storage systems. A computer readable medium may be considered a computer readable storage medium, for example, or a tangible storage device. 
     Moreover, a step or block that represents one or more information transmissions may correspond to information transmissions between software and/or hardware modules in the same physical device. However, other information transmissions may be between software modules and/or hardware modules in different physical devices. 
     The particular arrangements shown in the figures should not be viewed as limiting. It should be understood that other embodiments can include more or less of each element shown in a given figure. Further, some of the illustrated elements can be combined or omitted. Yet further, an example embodiment can include elements that are not illustrated in the figures. 
     While various aspects and embodiments have been disclosed herein, other aspects and embodiments will be apparent to those skilled in the art. The various aspects and embodiments disclosed herein are for purpose of illustration and are not intended to be limiting, with the true scope being indicated by the following claims.