Patent Publication Number: US-9432583-B2

Title: Method of providing an adjusted digital image representation of a view, and an apparatus

Description:
TECHNICAL FIELD 
     The present inventive concept relates to a method of providing an adjusted digital image representation of a view as well as an apparatus. 
     BACKGROUND 
     Due to the fast-paced development of consumer electronics in recent years, digital cameras are quickly becoming more and more capable. Modern digital cameras make it easy to capture a large number of images at each photo opportunity. A shooting opportunity may hence often result in several images of the same view, e.g. of the same object, the same person(s), the same animal(s), the same scenery, the same landscape, the same buildings etc. Some digital cameras even include built-in functionality for facilitating capturing of several images of a same view albeit using different configurations of the camera. This is sometimes referred to as bracketing wherein images are captured while varying for example the aperture value or the exposure setting of the camera. In view of the ever increasing number of captured images, there is a need for methods enabling efficient management, presentation and manipulation of large quantities of images having a similar image content. 
     SUMMARY OF THE INVENTIVE CONCEPT 
     An objective of the present inventive concept is to meet this need. A further object is to provide methods which, in addition to the former object, make use of image data from several images to provide technically improved images or in a user friendly manner. A further object is to enable these objects to be performed efficiently also on devices having limited displays of limited dimension. 
     According to a first aspect of the inventive concept there is provided a method of providing an adjusted digital image representation of a view, the method comprising: 
     providing a set of images, wherein the images of said set depict a same view and are captured with a digital camera using different configurations of the digital camera; 
     determining an initial representation of the view by providing a primary image based on image data of at least a first image of said set; 
     sending the primary image for presentation of the initial representation on a display; 
     providing a secondary image based on image data of at least a second image of said set, wherein the first image and the second image are different images captured using different configurations of the digital camera; and 
     sending, in response to receiving a user command, the secondary image for presentation of an adjusted representation of the view on the display. 
     An advantage of the inventive method is that the representation of the view may be easily adjusted by using data from different images of the image set. The image set may include a plurality of images captured using different camera configurations. Hence, the inventive method enables the user to adjust the representation of the view simply by entering an appropriate user command wherein an adjusted representation of the view may be provided. By using a set of images captured using different settings the extent of the adjustments may be increased. In case a single image had been used the bit depth of the single image could be a limiting factor for making adjustments to a greater extent than in the inventive method. 
     By first sending the primary image for presentation of the initial representation on the display, handling of the image set is simplified since only a single representation of the view needs to be presented to the user. The inventive method then enables the user to navigate, so to say, within the image set by selecting a desired adjustment. This may be more efficient than the user simultaneously being presented with many images (possibly of reduced scale) and then manually having to scan the images for the desired representation. This may be an especially valuable feature when viewing images on a device having a display of limited size, for example on a portable user device such as a smart phone. 
     The first image may be a predetermined image of said set for providing the primary image. 
     The method may further comprise selecting the second image from said set based on a predetermined indication indicating the second image as an image to be used for providing the secondary image. 
     The method may further comprise determining candidate images for providing the secondary image, the determining being based on a predetermined indication indicating at least two images of the set as candidate images, each of the at least two images being associated with a different user command; providing said different user commands to a user; receiving a user command; and determining the candidate image which is associated with the received user command, wherein the determined image is selected as the second image. This enables the user to apply a desired adjustment to the initial representation of the view simply by entering the appropriate user command. 
     According to one embodiment the method further comprises determining a first characteristic of the first image; analyzing said set to identify an image of said set presenting a second characteristic, different from said first characteristic; and selecting the identified image as the second image. The method may thus automatically identify an image of the image set which may be used for providing an adjusted representation of the view. The first and the second characteristic may be an exposure- or capture-related characteristic. 
     According to one embodiment the first and the second characteristic are determined by analyzing a data portion of the first image and a data portion of the second image, respectively. The analyzed data portions may include metadata. Additionally or alternatively the analyzed data portions may include image data. 
     According to one embodiment determining the first characteristic of the first image includes determining, for the first image, a first setting of a first parameter of the digital camera and a first setting of a second parameter of the digital camera, which second parameter is different from the first parameter, said first settings being used when capturing the first image; and wherein identifying an image of said set presenting a second characteristic includes identifying an image of said set which has been captured using the first setting of the first parameter and a second setting of the second parameter, which second setting is different from said first setting of the second parameter. This enables a well-defined adjustment to be applied to the initial representation since the secondary image depicting the adjusted representation will have a setting of at least one parameter in common with the primary image depicting the initial representation. 
     According to one embodiment the method further comprises associating the second image with a specific user command. The specific user command may be provided to a user. The user may thus apply the adjustment represented by the secondary image by supplying the specific user command. The user command may be provided by displaying it as a user selectable option on the display. 
     According to one embodiment the secondary image is provided in response to receiving the user command. The method may hence await providing or forming the secondary image until it is certain that the user desires the secondary image to be based on the second image. Unnecessary waste of processing power may thus be avoided. 
     The primary image may include image data of only the first image. Thus the primary image may be the first image. The secondary image may include image data of only the second image. Thus the secondary image may be the second image. 
     According to one embodiment the primary image is not based on image data of the second image. 
     According to one embodiment the secondary image is based on image data of the first and the second image. The adjusted representation of the view may thus be based on image data from more than one image wherein an adjusted representation of improved technical quality may be obtained. The embodiment for example enables formation of so-called High Dynamic Range (HDR) images. 
     According to one embodiment the primary image and the secondary image have the same image dimension. 
     According to one embodiment the method further comprises 
     determining, for the second image, a first setting of a third parameter of the digital camera being used when capturing the second image, which third parameter is different from the first and second parameter; 
     identifying a third image of said set which has been captured using the first setting of the first parameter, the second setting of the second parameter and a second setting of the third parameter; 
     providing a tertiary image based on image data of at least the third image of said set; and 
     sending, in response to receiving a further user command, the tertiary image for presentation of a further adjusted representation of the view on the display. 
     Once the adjusted representation has been obtained further adjustments may hence be performed. Since the tertiary image depicting the further adjusted representation will have a setting of at least one parameter in common with the secondary image depicting the adjusted representation this embodiment enables a well-defined further adjustment to be applied to the adjusted representation. 
     According to one embodiment the primary image is sent to a first user interface component presented on the display and the secondary image is sent to a second a second user interface component presented on the display. This enables a side-by-side comparison to of the initial and the adjusted representation to be made by the user. 
     According to one embodiment the primary image is sent to a first user interface component presented on the display and the secondary image is sent to the first user interface component. The adjusted representation may thus replace the initial representation on the display. This may be advantageous when the method is used on devices having a display of smaller size. The primary image and the secondary image may be displayed one at a time. 
     According to one embodiment the method further comprises 
     identifying a subset of images of said set, each image of said subset being captured using a same setting as the first image for at least one parameter of a set of parameters of the digital camera and a different setting than the first image for at least one capture-related parameter of said set of parameters; 
     associating a different user command with each image of said subset; 
     receiving a user command; and 
     determining the image of said subset which is associated with the received user command, wherein the determined image is selected as the second image. 
     Thus a plurality of available adjustments may be identified and each be associated with a different user command. The user may thus conveniently and efficiently apply the desired adjustment to the initial representation. More specifically the subset of images may be identified by comparing a setting of said at least one capture-related parameter for the first image to a setting of said at least one capture-related parameter for other images of said set. 
     According to one embodiment the method further comprises 
     identifying a subset of images of said set, each image of said subset being captured using a same setting as the first image for at least one parameter of a set of parameters of the digital camera and a different setting than the first image for exactly, i.e. no more and no less, one capture-related parameter of said set of parameters; 
     associating a different user command with each image of said subset; 
     receiving a user command; and 
     determining the image of said subset which is associated with the received user command, wherein the determined image is selected as the second image. 
     Thus a plurality of available adjustments may be identified and each be associated with a different user command. The user may thus conveniently and efficiently apply the desired adjustment to the initial representation. More specifically the subset of images may be identified by comparing a setting of said at least one capture-related parameter for the first image to a setting of said at least one capture-related parameter for other images of said set. A further advantage is that the adjustment may be applied in a controlled manner in that the setting of only one parameter may be changed at a time. 
     According to one embodiment providing the secondary image includes forming the secondary image by combining the first image and the second image based on an alpha value. The first and second image may be blended using the same alpha value for all pixels. The adjusted representation of the view may thus be based on image data from more than one image wherein an adjusted representation of improved technical quality may be obtained. The first image may be an image captured at a lower exposure value setting and the second image may be an image captured at a higher exposure value setting than the first image. The first image may be an image captured using a first focus point position and the second image may be an image captured using a second, different, focus point position. 
     According to one embodiment the method further comprises receiving a user indication of an image coordinate; and determining said alpha value based on the received image coordinate. The image coordinate may be a coordinate within the primary image. The user may thus vary the alpha value by selecting different points in the primary image. This provides for an intuitive way of controlling the blending of the first and the second image. 
     The alpha value may be determined in response to receiving the image coordinate by determining a first property value of a pixel of the first image, the pixel having a coordinate corresponding to the received image coordinate, and determining a second property value of a pixel of the second image, the pixel having a coordinate corresponding to the received image coordinate; and determining said alpha value based on the first and second property value. This provides for a computationally efficient blending operation which may be controlled by the user in real time even when used on a device having limited computational resources. The first and the second property values may for example correspond to a luminance value of a pixel of the first image and a luminance value of a pixel of the second image. The blending operation may thus be based on the exposure levels of the first and the second images. According to another example the first and the second property values may correspond to an image sharpness at a pixel of the first image and a pixel of a second image. The blending operation may thus be based on the sharpness levels of the first and the second images. 
     Alternatively, the alpha value may be determined by, in response to receiving the image coordinate, retrieving an alpha value at a coordinate of an alpha channel, which coordinate corresponds to the received image coordinate. The alpha channel may thus be used as a Look-Up-Table (LUT) for quickly determining the alpha value to be used for the blending operation. This provides for a computationally efficient blending operation which may be controlled by the user in real time even when used on a device having limited computational resources. 
     The alpha channel may be determined by applying a predetermined function to the first image and the second image. The predetermined function may include for each alpha value of the alpha channel, determining a first property value of a pixel of the first image and a second property value of a pixel of the second image and calculating said alpha value of the alpha channel using the first and second property values. The alpha channel may thus be determined on a pixel-level based on property values for both the first image and the second image. The first and the second property values may for example correspond to a luminance value of a pixel of the first image and a luminance value of a pixel of the second image. The blending operation may thus be based on the exposure levels of the first and the second images. According to another example the first and the second property values may correspond to an image sharpness at a pixel of the first image and a pixel of a second image. The blending operation may thus be based on the sharpness levels of the first and the second images. 
     According to a second aspect of the present inventive concept there is provided an apparatus for providing an adjusted digital image representation of a view, comprising: 
     processing means configured to determine an initial representation of the view by providing a primary image based on image data of at least a first image of a set of digital images, and further configured to provide a secondary image based on image data of at least a second image of said set, wherein the first image and the second image are different images. The set of digital images may be captured with a digital camera using different configurations of the digital camera. The apparatus further includes: 
     input means configured to receive a first user command; 
     output means configured to send the primary image for viewing of the initial representation on a display, and, in response to the input means receiving the first user command, send the secondary image for viewing of an adjusted representation of the view on the display. 
     The second aspect may generally present the same or corresponding advantages as the first aspect. Similarly the various method embodiments may be implemented also by the apparatus of the second aspect. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above, as well as additional objects, features and advantages of the present inventive concept, will be better understood through the following illustrative and non-limiting detailed description of preferred embodiments of the present inventive concept, with reference to the appended drawings, where like reference numerals will be used for like elements, wherein: 
         FIG. 1  is a schematic illustration of a user device according to one embodiment. 
         FIG. 2  is a flow chart of a method according to one embodiment. 
         FIGS. 3 a - c    illustrate a user interface according to one embodiment. 
         FIGS. 4 a - b    illustrate a user interface according to one embodiment. 
         FIGS. 5 a - c    illustrate a user interface according to one embodiment. 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     Detailed embodiments will now be described in connection with a user device  100  schematically illustrated in  FIG. 1 . The user device  100  may be a digital camera. The user device  100  may also be a personal digital assistant (PDA), a mobile phone, a smart phone or a tablet computer. Although the embodiments will be described in connection with a portable user device, the inventive concept may be implemented also in other types of electronics devices such as in a PC (stationary or laptop), a TV set, a video game console, a digital video recorder etc. 
     The user device  100  comprises display means. In  FIG. 1  the display means is embodied by a display  102 . The display  102  may be a Liquid Crystal Display (LCD), a Light Emitting Diode (LED) display. Display technologies per se are well known to the skilled person and will therefore not be elaborated further upon here. As described in more detail below the display  102  may be a touch sensitive display. 
     The user device  100  comprises processing means. In  FIG. 1 , the processing means is embodied by a processor  104 . The processor  104  may be configured to implement the methods in accordance with the present inventive concept as will be described in detail in the following. The processor  104  may be implemented as one or more field programmable gate arrays (FPGAs), applications specified integrated circuits (ASICs), or the like, wherein the methods of the present inventive concept may be implemented using a hardware description language (HDL). The processor  104  may also be implemented as central processing unit (CPU) of the user device  100 , a graphics processing unit (GPU) of the user device  100  or a dedicated image processing unit of the user device  100  configured to implement methods in accordance with the present inventive concept, wherein the methods of the present inventive concept may be implemented using low- or high-level software instructions stored in the user device  100  for execution by the processing unit. 
     The user device  100  comprises storage means. In  FIG. 1  the storage means is embodied by a memory  106 . The memory may include a data section for storing digital images. The data memory may be e.g. a random access memory (RAM) integrated in the user device  100  or a flash memory provided on a memory card removably inserted in the user device  100 . The memory  106  may further include a program memory for storing software instructions for the processor  104 . The program section may e.g. be a RAM or a ROM integrated in the user device  100 . 
     The user device  100  and the components thereof operate under the supervision of an operating system  108 . The operating system  108  may be stored in the memory  106  or in another dedicated memory. 
     The user device  100  comprises input means. In  FIG. 1  the input means is embodied by a man-machine interface  110  (MMI). The MMI  110  may include one or more physical buttons, scroll wheels, joysticks, track balls or the like. The MMI  110  may also include peripheral devices, such as a mouse and/or a keyboard. The display  102  of the user device  100  may be a touch sensitive display wherein virtual buttons may be presented on the display  102  and the user may enter commands by touching the display  102 . The MMI  110  may also provide gestures wherein the user may interact with the user device  100  for example by making swiping, tapping or pinching gestures on the display  102 . The display  102  may be a resistive touch screen, a capacitive touch screen. Touch screen technologies per se are well known to the skilled person and will therefore not be elaborated further upon here. 
     The methods of the present inventive concept may also be implemented as a computer program product  116  comprising one or more software components. The software components may comprise software instructions that when downloaded to a processor are configured to perform the instructions corresponding to the methods. 
     According to an embodiment which will be described with reference to  FIGS. 1-3  a set of digital images (hereinafter referred to as the image set) are provided at the user device  100  (box  202 ). The image set may be stored in the memory  106 . The images of the set may be stored as separate image files (e.g. in JPEG, TIFF or DNG format etc.). The set may be formed for example by storing the separate image files in a common subdirectory of the memory  106 . The set may also be formed by storing references to the image files in a set file which may be read and interpreted by the processor  104 . The images of the image set may be captured at the same resolution, i.e. the images may have an identical image dimension. 
     The images of the image set may depict a same view. “A same view” is intended to be construed broadly in the sense that the images need not depict exactly the same view but may have been captured from slightly different viewpoints. This may be the result of comparably minor movements (possibly unconscious) of the camera between the captures. There may also be slight variations between the various view representations of the images due to changes within the view between the captures. For example an object within the view may change its position or a person may change expression or posture. Preferably the images are similar in such a way that they depict the same view (comprising the same photographic elements) and are taken in succession with a fairly small temporal distance in between the captures. Commonly the images have been captured using the same digital camera. However, it is contemplated that the images also may have been captured by different digital cameras. The images of the image set may be captured using different camera configurations. The digital camera may be setup according to a plurality of configurations. Each configuration may include a specific setting of one or more adjustable parameter of the digital camera. 
     The processor  104  determines an initial representation of the view by providing an image (box  204 ), said image forming the initial representation of the view. This image will in the following be referred to as the primary image. 
     The processor  104  may select one image of the image set as the primary image. The primary image may thus include image data from only one image of the image set. In other words the selected image is the primary image. Alternatively, the processor  104  may retrieve image data from two or more images of the image set and provide the primary image by combining the retrieved image data. The primary image may thus include image data from more than one image of the image set. Such a scenario will be described in more detail below. 
     The memory  106  may store an indication of which image(s) of the image set form(s) the primary image. The indication may for example be stored in the above-mentioned set file. In the case of combined images the memory  106  may further include an indication of how the images should be combined into the primary image (see below). The processor  104  may read the indication and access the image(s) from the memory  106 . The indication may simply be a default value. The indication may alternatively have been provided by the user previously indicating the file name of the image constituting the primary image. The processor  104  may alternatively select the primary image automatically. The processor  104  may for example select the image of the image set having the earliest time stamp as the primary image. The processor  104  may for example select the first image of the image set when ordered in an alphabetical fashion by their file names. 
     As the primary image has been provided by the processor  104  the initial representation of the view may be presented to the user by displaying the primary image on the display  102  (box  206 ). This is illustrated in  FIG. 3 a    wherein a schematic primary image depicting inter alia a group of trees  304  and a person  306  is displayed in a user interface (UI) component  300  on the display of the user device  100 . 
     The processor  104  may then identify the available adjustments of the initial representation by analyzing the image set as follows: The processor  104  may analyze the images of the image set to determine characteristics of each image. The characteristics may be capture- or exposure-related characteristics. For example the processor  104  may determine a brightness value and/or a contrast value for each image of the image set. The value may be determined by analyzing image data of each image. The value may be a mean value calculated for at least a portion of each image of the image set. Assuming by way of example that the determined (brightness or contrast) values for some of the images are higher, and for some of the images are lower than the (brightness or contrast) value of the primary image, an available adjustment may be to increase or decrease the (brightness or contrast) value of the initial representation of the view. 
     A characteristic may also include a setting of one or more parameters of the camera used when capturing the images. The characteristic may thus pertain to a camera configuration. The processor  104  may analyze characteristics pertaining to one or more of the camera parameters aperture, exposure time, exposure value, flash usage, flash strength, flash synchronization speed, color settings, white balance, focus point and exposure index rating (EI or ISO). The characteristics may be determined by the processor  104  analyzing capture information associated with each image of the image set. The capture information may be stored in the memory  106 . The capture information may be stored in a metadata portion for each image. The capture information may be stored in accordance with the Exchangeable image file format (EXIF). The capture information may be stored in accordance with the Extensible Metadata Platform (XMP). The metadata may be stored in each image file or in so-called sidecar files. 
     The processor  104  may determine each different configuration used when capturing the image set as an available adjustment. In other words the processor  104  may determine a first characteristic of the primary image and then identify images of the image set presenting a characteristic, different from the first characteristic. The characteristic of each identified image may then be considered to represent an available adjustment of the initial representation of the view. In other words, the initial representation may be adjusted in accordance with any one of the characteristics of the identified images. 
     According to the illustrated example the image set may include: 
     a first image captured using a first aperture value and without flash; 
     a second image captured using a second aperture value, smaller than the first aperture value, and without flash; 
     a third image captured using a third aperture value, larger than the first aperture value, and without flash; 
     a fourth image captured with standard flash strength and using the first aperture value; 
     a fifth image captured with standard flash strength and using the second aperture value; 
     a sixth image captured with standard flash strength and using the third aperture value; 
     a seventh image captured with reduced flash strength using the first aperture value; and 
     an eighth image captured with increased flash strength using the first aperture value. 
     Assuming that the first image is selected as the primary image, the following options may be presented to the user: 
     1. Set the aperture value to the second aperture value and do not turn on the flash. 
     2. Set the aperture value to the third aperture value and do not turn on the flash. 
     3. Set the aperture value to the first aperture value and turn on the flash at standard strength. 
     4. Set the aperture value to the second aperture value and turn on the flash at standard strength. 
     5. Set the aperture value to the third aperture value and turn on the flash at standard strength. 
     6. Set the aperture value to the first aperture value and turn on the flash at reduced strength. 
     7. Set the aperture value to the first aperture value and turn on the flash at increased strength. 
     The method hence enables an emulation of the capturing conditions prevailing during the actual image capture. 
     Alternatively, the available adjustments may be presented such that one setting may be varied at a time. Returning to the illustrated embodiment in  FIG. 3 a    the above-mentioned first image of the image set has been selected as the primary image. The processor  104  analyzes the first image and determines that it has been captured using a first setting of a first parameter (i.e. no flash) and a first setting of a second parameter (i.e. the first aperture value). The processor  104  then analyzes the remaining images of the image set. The processor  104  determines that the second image has been captured with the same setting of the first parameter as the first image (i.e. no flash) and a different setting of the second parameter than the first image (i.e. the second aperture value). Analogously, the processor  104  determines that the third image has been captured with the same setting of the first parameter as the first image and a different setting of the third parameter than the first image (i.e. the third aperture value). Additionally the processor  104  determines that the fourth image has been captured with a different setting of the first parameter than the first image (i.e. standard flash) and the same setting of the second parameter as the first image (i.e. the first aperture value). Accordingly, the adjustments  308 ,  310 ,  312  are presented on the display  102  in the user interface component  302 . It should be noted that the illustrated arrangement and the relative dimensions of the user interface components  300  and  302  in  FIG. 3 a    only constitute one possible example. 
     The processor  104  determines that the remaining images of the image set have been captured with different settings of both the first and second parameter compared to the first image. The remaining images are therefore determined to not represent available adjustments of the initial representation of the view. In other words, only images of the image set having a setting of at least one parameter in common with the first image and a different setting of only one capture-related parameter than the first image may be determined to represent available adjustments of the initial representation. 
     It should be noted that each image of the image set may present settings of more parameters than aperture and flash, for example any of parameters discussed above in connection with the camera may be used. The processor  104  may be configured to consider the settings of only a subset of the available parameters of the images. The subset of parameters to be considered may for example be indicated in the above-mentioned set file. Alternatively, it may be a user configurable option wherein the user may indicate the parameter subset by ticking appropriate boxes in a dialog or a configuration form accessible on the user device  100 . 
     The available adjustments may also be determined in alternative manner. The memory  106  may include a set of indications indicating a number of images of the set as candidate images for providing an adjusted representation of the view. The indications may be stored in the above-mentioned set file. The indications may be stored in the candidate images. The set of indications may for example have been provided by the user previously indicating the file names of the images constituting candidate images. The capturing process during which the image set has been captured may also be fixed in the sense that images are captured with a number of predetermined different camera settings which are known to the processor  104 . The set of indications may be provided as software instructions instructing the processor  104  which images of the image set are candidate images (e.g. by referring to their number in the sequence or using a standardized naming of the image files). The processor  104  may thus determine what adjustments of the initial representation are available, i.e. what candidate images are available. The indication may indicate what type of adjustment the candidate image pertains to. Each available adjustment may be presented as a selectable option on the display  102 , wherein the user may select one of the options to effect the desired adjustment of the initial representation of the view. Hence, each candidate image may be associated with a different user command. It is contemplated that the available adjustments need not be presented on the display  102 . Instead each of the available adjustments may be associated with a specific command which may be entered using the MMI  110 . In case the display  102  is a touch sensitive display the available adjustments may be effected by using the appropriate touch command, e.g. a double tap to adjust the initial representation in accordance with a first candidate image, a left swipe and a right swipe to adjust the initial representation in accordance with a second and third candidate image, respectively. The specific command to be associated with each candidate image may be included in the set of indications. Alternatively the commands may be assigned in accordance with a default configuration. 
     Different sets of candidate images may be provided for each image of the set. In analogy with the above-described embodiment, a set of candidate images for the first image may include only images of the image set having a setting of at least one parameter in common with the first image and a different setting of only one capture-related parameter than the first image. 
     Returning to the illustrated embodiment of  FIG. 3 a    the user may select one of the adjustments  308 ,  310 ,  312  by entering the appropriate command using the MMI  110 . It is contemplated that the available adjustments need not be presented on the display  102 . Instead each of the available adjustments may be associated with a specific command which may be entered using the MMI  110 . In case the display  102  is a touch sensitive display the available adjustments may be effected by using the appropriate touch command, e.g. a double tap to turn on the flash, a left swipe to decrease the aperture value and a right swipe to increase the aperture value. 
     The MMI  110  receives the user command associated with one of the available adjustments. In response thereto, the processor  104  provides an image representing the view in accordance with the selected adjustment (box  208 ). If the user selects adjustment  308  the processor  104  selects the fourth image for the adjusted representation. If the user selects the adjustment  310  the processor  104  selects the second image for the adjusted representation. If the user selects the adjustment  312  the processor  104  selects the third image for the adjusted representation. In either case the provided image thus includes image data from only one image of the image set. 
     In the case illustrated in  FIG. 3 b   , the user has selected adjustment  310  wherein the second image is presented in the user interface component  300  (box  210 ). As schematically indicated the sharpness of the trees  304  as a result has decreased. 
       FIG. 3 c    illustrates an alternative scenario wherein the user instead has selected adjustment  308  in  FIG. 3 a   . In response thereto the fourth image is presented in the user interface component  300 . As schematically indicated the person  306  is illuminated. 
     After presenting the appropriate image, the process may proceed in analogy with the above. The processor  104  may identify the images of the image set having a setting of at least one parameter in common with the image illustrating the adjusted representation of the view. In the situation illustrated in  FIG. 3 b    the processor  104  may determine that the aperture value may be increased (adjustment  312 ) using the first image and that the flash may be turned on using the fifth image (adjustment  308 ). 
     In the situation illustrated in  FIG. 3 c    the processor  104  may determine that the aperture value may be decreased (adjustment  310 ) using the fifth image, that the aperture value may be increased (adjustment  312 ) using the sixth image, that the flash strength may be reduced (adjustment  314 ) using the seventh image and that the flash strength may be increased (adjustment  316 ) using the eighth image. Although left-out for clarity from  FIG. 3 c    the flash may also be turned off using the first image. 
       FIG. 4 a    illustrates a user interface according to an alternative embodiment. The alternative embodiment is in most parts identical to the embodiment illustrated in  FIGS. 3 a - c    but differs in that the user interface includes a first UI component  400   a  and a second UI component  400   b . The primary image (i.e. the initial representation of the view) is displayed in the UI component  400   a . The UI component  400   b  is provided adjacent to the UI component  400   a . Initially the UI component  400   b  is empty, i.e. does not display any digital image. The available adjustments which are the same as in  FIG. 3 a    are displayed in the UI component  402 . In  FIG. 4 b    the user has selected the adjustment  402  wherein the adjusted representation of the initial view is presented to the user by displaying the second image in the user interface component  400   b . The first image and the second image are thus presented in a side-by-side manner enabling easy evaluation of the adjustment for the user. 
     As mentioned above the primary image may include image data from more than one image of the image set. Also the adjusted representation of the initial view may be provided by combining image data from more than one image of the image set. These aspects may be better understood from the embodiment illustrated in  FIGS. 5 a   - c.    
     An image set is provided. The image set includes inter alia images  520   a  and  520   b . The image  520   a  and the image  520   b  present different characteristics. In the image  520   a  the exposure level is acceptable in the part depicting the trees  504  but too high in the part depicting the person  506 , thus resulting in the person  506  being overexposed. In the image  520   b  the exposure level is acceptable in the part depicting the person  506  but too low in the part depicting the trees  504 , thus resulting in the trees  504  being underexposed. In other, more general terms, the image  520   a  image has been captured using a higher exposure value setting and the image  520  has been captured using a lower exposure value setting of the camera. 
     According to the illustrated example the image  520   a  is selected as the primary image, i.e. as the initial representation of the view. The processor  104  may in analogy to the previously described embodiments analyze the set of images and determine that the image set includes an image  520   b  captured at a lower exposure value than the image  520   a . The processor  104  may make this determination by analyzing metadata of the images. Alternatively or additionally the processor  104  may make this determination by analyzing image data of the images. The processor  104  may for example determine that the image  520   b  presents a lower overall brightness level than the image  520   a . The processor  104  may thus determine that a so-called High Dynamic Range (HDR) image may be formed by combining image data from the image  520   a  with image data from the image  520   b . In response HDR adjustment  514  is presented in the user interface component  502  (see  FIG. 5 b   ). Completely analogously to the previous embodiments, further adjustments  510 ,  512  may depending on the image set be available and presented to the user. 
       FIG. 5 c    illustrates the scenario where the user has chosen the HDR adjustment  514 . The processor  104  then determines the adjusted representation of the view by forming an image  520   c  including image data from the image  520   a  and image data from the image  520   b . The image  520   c  is presented in the user interface component  500 . The image  520   c  may be formed by blending image data from the images  520   a ,  520   b  together. The blending operation may include alpha blending the images  520   a , and  520   b.    
     It should be noted that the process may flow in the reverse direction as well. The image  520   c  may hence be selected as the primary image wherein the processor  104  may determine that one of the available adjustments is to turn HDR off, corresponding to adjustment  516  in  FIG. 5   c.    
     According to one embodiment there is provided a method for adjusting the image  520   c . According to this embodiment the user may input an image coordinate to the user device  100  via the MMI  110 . In case the user device  100  includes a touch screen the user may e.g. tap at a point within the image  520   c . In case the MMI  110  includes a pointer device (such as a mouse, a joystick, a track ball) the user may steer a pointer shown on the display  102  to a desired location in the image wherein the image coordinate of the indicated location may be determined. 
     In response to receiving the image coordinate the processor  104  may determine a first property value of a pixel of the image  520   a , the pixel having a coordinate corresponding to the received image coordinate. Analogously, the processor  104  may determine a second property value of a pixel of the image  520   b , the pixel having a coordinate corresponding to the received image coordinate. Denoting the received image coordinate (x i , y i ), the property value of the pixel of the image  520   a  having the coordinate (x i , y i ) and the property value of the pixel of the image  520   b  having the coordinate (x i , y i ) may be determined. Based on the first and second property value an alpha value α for forming an updated version of the image  520   c  may be determined. 
     More specifically, the first property value may be the luminance value L 1  of the pixel of the first image. The second property value may be the luminance value L 2  of the pixel of the second image. Using the first property value, a first relative property value R 1  may be calculated. The first relative property value R 1  may indicate the deviation of the first property value from a predetermined threshold value L T . Analogously, using the second property value, a second relative property R 2  value may be calculated. The second relative property value R 2  may indicate the deviation of the second property value from the predetermined threshold value L T . The predetermined threshold value may be determined to be close to a half of the maximum value of the first and second property value. In the context of the luminance values L 1 =[0, 255] and L 2 =[0, 255] (assuming an 8-bit representation) a relative property value R j  (for j=1, 2) may be determined using the following formula:
 
 R   j =129 −|L   j   −L   T |,
 
     where L T  may be set to 128. The image  520   a  may be selected as the foreground image and the image  520   b  may be selected as the background image. The alpha value α may then be calculated as a ratio between the first relative property value and the sum of the first and the second relative property value, i.e. α=R 1 /(R 1 +R 2 ). From this formula it may be understood that the value  129  when calculating R j  has been chosen to avoid division by zero in case both L 1  and L 2  are equal to 255 or 0. Other choices are possible for example any value in the range 130-140 may be used purely by way of example. Alternatively, the image  520   b  may be selected as the foreground image and the image  520   a  may be selected as the background image. The alpha value α may then be calculated as a ratio between the second relative property value and the sum of the first and the second relative property value, i.e. α=R 2 /(R 1 +R 2 ). 
     As will be appreciated by the skilled person these formulas only constitute one possible example within the scope of the invention and that other choices also are possible. For example other functions for calculating the deviation of the luminance value from the threshold value L T  may be chosen which exhibit a smaller change in a region of luminance values close to L T . Moreover, the method may rely on a look-up-table (LUT) mapping the full range of luminance values to a respective relative property value. The calculation of R j  may thus be replaced with retrieving a correct value from the LUT. 
     Once the alpha value has been determined, the images  520   a  and  520   b  may be blended together. Assuming  520   a  image is selected as the foreground image and the image  520   b  is selected as the background image, any pixel i at the coordinate (x i , y i ) in the combined image may be calculated by blending the pixel at coordinate (x i , y i ) of the image  520   a  and the pixel at coordinate (x i , y i ) of the image  520   b  using the following formula:
 
 V   520c, (xi, yi) =(1−α)* V   520b, (xi, yi) +α* V   520a, (xi, yi)  
 
     Alternatively, the alpha value α may be retrieved from an alpha channel. In response to receiving the image coordinate (x i , y i ) the alpha value at the position in the alpha channel corresponding to the coordinate (x i , y i ) may be retrieved. The alpha channel may include a two-dimensional matrix having the same dimensions as the first and the second image wherein each element of the matrix includes the alpha value for a pixel at a corresponding position in the first or the second image. In this sense the alpha channel may be represented by an image including pixels, wherein a pixel at coordinate (x i , y i ) may indicate an alpha value for a pixel at coordinate (x i , y i ) in the image  520   a  and the image  520   b.    
     The alpha channel may be a predetermined alpha channel. Alternatively, the alpha channel may be determined based on the first and the second image. The alpha channel may for example be determined in response to the processor  104  selecting the image  520   b  from the image set. The alpha channel may be calculated in respect of either one of the images  520   a  or  520   b . In the following it will be assumed that the image  520   a  is selected as the foreground image and that the image  520   b  is selected as the background image. The alpha channel may be determined by applying a predetermined function to the image  520   a  and the image  520   b . More specifically each pixel (x i , y i ) of the alpha channel may be determined as follows: A first property value (e.g. luminance value L 1 ) of a pixel at coordinate (x i , y i ) of the image  520   a  and a second property value (e.g. luminance value L 2 ) of a pixel at coordinate (x i , y i ) of the image  520   b  may be determined. The alpha value of the alpha channel for coordinate (x i , y i ) may then be calculated using the formula: α=R 1 /(R 1 +R 2 ), wherein R 1  and R 2  are the relative property values as defined above. 
     In a preferred usage scenario, the user may repeatedly provide new image coordinates (e.g. by tapping at or by moving a pointer to different locations in the combined image  520   c ) wherein an updated image  520   c  may be formed using any one of the above-mentioned methods and then presented on the display  102 . The user may thus interactively control the blending operation. Due to the efficiency of the method this functionality may be provided also on hardware having limited processing capacity. 
     The above-described method has a more general applicability in that it may be used in combination with other types of pixel properties than luminance. For example the first property value may be a saturation value and the second property value may be a saturation value, wherein corresponding relative saturation property values may be calculated in the same manner as described above. The relative saturation property values may then be used calculate a single alpha value or an alpha channel image, in a manner completely analogous to the above. 
     According to another example, the method may be applied to a scenario wherein images  520   a  and  520   b  have been captured with different settings of the focus point. Different parts of the depicted view may thus be sharp in the images  520   a  and  520   b . The first property value may be determined for the image  520   a  by high pass filtering the image  520   a . The high pass filtering may be implemented by applying a discrete Laplace transform to the image  520   a . The transform may be determined by convolving the image with the kernel: 
     
       
         
           
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                     1 
                   
                   
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                     0 
                   
                   
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     Each pixel (x i , y i ) of the transformed image includes a property value (i.e. the first property value) for the pixel (x i , y i ) of the image  520   a . The second property value of the image  520   b  may be determined in a completely analogous manner wherein each pixel (x i , y i ) of the transformed image includes a property value (i.e. the second property value) for the pixel (x i , y i ) of the image  520   b.    
     Denoting the first property value as D 1  for a pixel (x i , y i ) of the image  520   a  and the second property value as D 2  for a pixel (x i , y i ) of the image  520   b  a respective alpha value may be determined as α=D 1 /(D 1 +D 2 ) (assuming that the image  520   a  is selected as the foreground image and that the image  520   b  is selected as the background image). Analogously to the above methods the alpha value may be calculated in response to the user inputting the image coordinates using the MMI  110  or by retrieving an alpha value from an alpha channel. 
     Using the method, the user may provide image coordinates in a region of an image wherein, assuming that one of the images  520   a ,  520   b  are sharp in said region, a combined image which is sharp in the desired region may be obtained. The user may thus interactively adjust the focus point in the image. 
     The above-described methods of combining images based on an alpha value may be regarded as an inventive aspect quite independent from the inventive aspects embodied in  FIGS. 1-4 . Thus, there is provided a method for combining images comprising: forming a combined image from a first image and a second image. The first image and the second image may depict a same view. The first and the second image may thus be similar in that they include the same photographic elements. The first image may be captured using a first camera setting and the second image may be captured using a second camera setting, different from the first setting. The first image may present a higher exposure level than the second image. The first image may be captured with a different focus point position than the second image. The first and second image may be combined based on an alpha value. The first and second image may be blended using the same alpha value for all pixels of the combined image. 
     The method may further comprise receiving a user indication of an image coordinate. The image coordinate may be an image coordinate of the first image or the second image. The image coordinate may be a pixel coordinate. The alpha value may be determined based on the received image coordinate. In response to receiving the image coordinate a first property value of a pixel of the first image may be determined, the pixel having a coordinate corresponding to the received image coordinate. Furthermore, a second property value of a pixel of the second image may be determined, the pixel having a coordinate corresponding to the received image coordinate. The alpha value may then be determined based on the first and second property value. 
     Alternatively, the alpha value may be determined by, in response to receiving the image coordinate, retrieving an alpha value at a coordinate of an alpha channel, which coordinate corresponds to the received image coordinate. The alpha channel may be a predetermined alpha channel. The alpha channel may be determined by applying a predetermined function to the first image and the second image. The predetermined function may include: for each alpha value of the alpha channel, determining a first property value of a pixel of the first image and a second property value of a pixel of the second image and calculating said alpha value of the alpha channel using the first and second property values. The pixel of the first image may have a coordinate corresponding to the received image coordinate. Similarly the pixel of the second image may have a coordinate corresponding to the received image coordinate. Hence by the user providing different image coordinates a different combined image may be formed. The method may be implemented in a device as discussed in connection with  FIGS. 5 a - c    above. 
     In the above, methods have been described in connection with a user device  100 . However it is contemplated that the methods may be used in other scenarios as well. The image set may be stored at a server connected to a network, such as the Internet. A user device may connect to the server via the network. The server may include input and output means for sending and receiving data to/from the user device via the network. The input and output means may be e.g. be realized by a Network Interface Card (NIC). The server may provide the image set to the user device wherein the user device may download the image set from the server. The user device may further download software instructions (e.g. in the form of Java, HTML, JavaScript or a combination thereof) implementing any one of the above-described methods. The user interface may hence be provided in the form of a web page. The web page may be displayed in a web browser running on the user device. A processor of the user device may then perform the respective method accordingly. Alternatively, processing means of the server may determine the initial representation of the view in any one of the above-described manners and send the primary image depicting the initial representation the user device using the output means. Upon receiving the primary image, the user device may present the image on a display thereof. The server may further, in a manner analogous to the above described methods, determine the available adjustments and provide user commands to the client device for effecting each adjustment. Similar to the above scenario, the user interface may be provided in the form of a web page. The web page may be displayed in a web browser running on the user device. The provided user commands may be presented on the web page. The user may apply one of the available adjustments by selecting one of the provided user commands, e.g. by selecting the appropriate option on the web page. The server may receive the user command via the input means (e.g. via the NIC). In response thereto an image depicting the adjusted representation may be sent to the client device for presentation. The image may e.g. be presented on the web page. 
     In the above the inventive concept has mainly been described with reference to a limited number of examples. However, as is readily appreciated by a person skilled in the art, other examples than the ones disclosed above are equally possible within the scope of the inventive concept, as defined by the appended claims.