Patent Publication Number: US-2020296301-A1

Title: Image processing arrangement

Description:
FIELD OF THE INVENTION 
     The present invention relates to processing of respective pieces of image data obtained from a visual light camera and from a thermographic camera that at least partially share a field of view. 
     BACKGROUND 
     For example many search and surveillance solutions at least partially rely on visual information obtained via usage of a camera assembly that may include one or more camera modules or camera units that may applied to capture still images and/or video stream depicting a location of interest. Such solutions involve portable devices that may be brought to the site of usage to capture images/video to depict locations of interest that may be non-accessible for direct visual inspection or fixed installations arranged to constantly monitor an area or space of interest. 
     A specific example of using such a camera assembly involves so-called search camera device, such as Savox SearchCam 3000. Such a device involves a camera assembly arranged in one end of an elongated shaft and a display unit arranged in or close to another end of the shaft, which display unit is arranged to display the current camera view to a user of the search camera device e.g. to enable locating victims or items of interest in collapsed buildings, inspecting underwater locations or objects, etc. Some search camera devices enable switching between normal camera operation and infrared camera operation in order to provide the user with the possibility of making use the part of the electromagnetic spectrum that provides the most useful visual information under the current operating conditions. 
     SUMMARY 
     An object of the present invention is to provide a technique that enables obtaining enhanced visual information for improved detection of objects of interest when used e.g. in a search camera device of a type described in the foregoing. 
     In the following a simplified summary of some embodiments of the present invention is provided in order to facilitate a basic understanding of some aspects of the present invention. The summary is not an extensive overview of the invention. It is neither intended to identify key or critical elements of the invention nor to delineate the scope of the invention. The following summary merely presents some concepts of the invention in a simplified form as a prelude to a more detailed description of exemplifying embodiments of the invention. 
     In accordance with an example embodiment, an image processing apparatus is provided, the apparatus comprising at least one processor and at least one memory including computer program code for one or more programs, the at least one memory and the computer program code configured to, with the at least one processor, cause the apparatus to perform at least the following: obtain a first image and a second image that at least partially illustrate the same real-world scene, wherein the first image comprises a visible light image and the second image comprises a thermal image; identify one or more spatial portions of the second image that represent a predefined temperature range; identify one or more spatial portions of the first image that illustrate the same portions of the real-world scene as illustrated in the identified one or more spatial portions of the second image; and derive, based on the first image, a composite image wherein the identified one or more spatial portions of the first image are emphasized. 
     In accordance with another example embodiment, an image capturing apparatus is provided, the apparatus comprising a camera assembly comprising a first imaging device for capturing visible light images and a second imaging device for capturing thermal images, the first and second cameras positioned with respect to each other such that they have at least partially overlapping respective fields of view; and an image processing apparatus according to the example embodiment described in the foregoing. 
     In accordance with another example embodiment, a search camera apparatus is provided, the apparatus comprising an elongated shaft, a display and an image capturing apparatus according to the example embodiment described in the foregoing, wherein the camera assembly is arranged at one end of the elongated shaft; the display is arranged in or close to the other end of the elongated shaft, and the image processing apparatus is further caused to provide the composite image for rendering on the display. 
     In accordance with another example embodiment, a method for image processing is provided, the method comprising: obtaining a first image and a second image that at least partially illustrate the same real-world scene, wherein the first image comprises a visible light image and the second image comprises a thermal image; identifying one or more spatial portions of the second image that represent a predefined temperature range; identifying one or more spatial portions of the first image that illustrate the same portions of the real-world scene as illustrated in the identified one or more spatial portions of the second image; and deriving, based on the first image, a composite image wherein the identified one or more spatial portions of the first image are emphasized. 
     According to another example embodiment, a computer program is provided, the computer program comprising computer readable program code configured to cause performing at least a method according to the example embodiment described in the foregoing when said program code is executed one or more computing apparatuses. 
     The computer program according to an example embodiment may be embodied on a volatile or a non-volatile computer-readable record medium, for example as a computer program product comprising at least one computer readable non-transitory medium having program code stored thereon, the program which when executed by one or more apparatuses causes the one or more apparatuses at least to perform the operations described hereinbefore for the computer program according to an example embodiment of the invention. 
     The exemplifying embodiments of the invention presented in this disclosure are not to be interpreted to pose limitations to the applicability of the appended claims. 
     The verb “to comprise” and “to include” as well as their derivatives are used in this disclosure to refer to an open limitation that does not exclude the existence of also unrecited features. Moreover, it is to be understood that the use of “a” or “an”, i.e. a singular form, throughout this document does not exclude a plurality. Furthermore, features described in the foregoing are mutually freely combinable unless explicitly stated otherwise. 
     Some features of the invention are set forth in the appended claims. Aspects of the invention, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of some example embodiments when read in connection with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       Non-limiting exemplifying embodiments of the present invention and some of their advantages are explained in greater detail in the following with references to the accompanying drawings, in which: 
         FIG. 1  illustrates a block diagram of some logical elements of an image capturing apparatus according to an example; 
         FIG. 2  illustrates a block diagram of some logical elements of the image processing apparatus according to an example; 
         FIG. 3  illustrates a method according to an example; 
         FIG. 4  schematically illustrates a search camera apparatus according to an example; and 
         FIG. 5  illustrates a block diagram of some elements of an apparatus according to an example. 
     
    
    
     DETAILED DESCRIPTION OF NON-LIMITING EXAMPLE EMBODIMENTS 
       FIG. 1  illustrates a block diagram of some logical elements of an image capturing apparatus  100  according to an example. The image capturing apparatus  100  comprises a camera assembly  110  that is communicatively coupled to an image processing apparatus  120  via a communication link  130 . In this regard, the camera assembly  110  comprises a first camera  111  and a second camera  112 , each of which is communicatively coupled to the image processing apparatus  120 . In other examples, the image capturing apparatus  100  may include further entities and/or some entities depicted in  FIG. 1  may be combined with other entities. 
     The communicative coupling may enable transferring the respective images captured by the first camera  111  and the second camera  112  from the camera assembly  110  to the image processing apparatus  120  and enable transferring control information from the image processing apparatus  120  to the camera assembly  110 . The communicative coupling may further enable transferring other information between the camera assembly  110  and the image processing apparatus  120 . The communicative coupling may be provided, for example, using wired or wireless communication link between the camera assembly  110  and the image processing apparatus  120 . As an example in this regard, the coupling may be provided via one or more electrical wires and/or one or more optical links such as optical fibers. In another example, the communicative coupling may be provided via usage of a short-range wireless communication technique known in the art, such the wireless local area networking according to IEEE 802.11 series of standards (e.g. Wi-Fi) or the personal area networking according to the Bluetooth™ standards. In a further example, the communicative coupling may be provided via usage of cellular communication technologies known in the art. 
     The image processing apparatus  120  may be arranged to compose an image based on respective image data received from the first camera  111  and/or the second camera  112 . Hence, the image composed by the image processing apparatus  120  may comprise an image captured by the first camera  111  or a derivative thereof, an image captured by the second camera  112  or a derivative thereof, or a composite image composed based on a temporally aligned respective images captured by the first camera  111  and the second camera  112 . In the following, for clarity and brevity of description, the term composite image is applied to refer to the image derived by the image processing apparatus  120  for presentation to the user, even though in some scenarios it may not comprise a true composite image but rather an image derived based on an image captured by the first camera  111  or on an image captured by the second camera  112 . 
       FIG. 1  serves to illustrate logical components of the image capturing apparatus  100  and hence does not impose structural limitations concerning implementation of the image capturing apparatus  100 . As an example, the first camera  111  and the second camera  112  may be provided as separate entities that are both included in the camera assembly  110 , whereas in another example the first camera  111  and the second camera  112  may be provided as single entity where the first camera  111  and the second camera  112  may be independent sub-entities or where the first camera  111  and the second camera  112  may share some components within the single entity that serves to provide the first and second cameras  111 ,  112 . As another example, the image processing apparatus  120  may be provided as one or more entities that are arranged to (possibly jointly) provide the functionality described in the foregoing. In this regard, the image processing apparatus  120  may be provided as respective hardware or as a combination of hardware and software arranged to implement the functionality described for the image processing apparatus  120  in the foregoing. 
     The first camera  111  may be provided for capturing images using visible light and the second camera  112  may be provided for capturing using infrared (IR) radiation. The first camera  111  that makes use of visible portion of the electromagnetic radiation spectrum may be also referred to e.g. as a visible light camera or as a normal camera, whereas the second camera  112  that makes use of the IR portion of the electromagnetic radiation spectrum may be also referred to e.g. as an infrared camera (an IR camera), as a thermographic camera or as a thermal imaging camera. The first camera  111  may be arranged to capture visible light images based on received electromagnetic radiation at a first range of wavelengths whereas the second camera  112  may be arranged to capture thermal images based received electromagnetic radiation at a second range of wavelengths, where the second range covers wavelengths that longer than those of the first range. Typically, the first range covers wavelengths approximately in the range from 400 to 700 nanometers (nm), whereas the second range covers wavelengths from 700 nm onwards, e.g. from 700 to 1000 nm. In some examples, the second range may further extend to longer wavelengths, e.g. up to wavelengths in the microwave range (e.g. up to several thousand nanometers). 
     The first camera  111  may comprise, for example, a digital camera unit or module arranged capture color images. In another example, the first camera  111  may comprise a digital camera unit or module arranged to capture monochrome images, such as grayscale images. In a further example, the first camera  111  may comprise a digital camera unit or module arranged to selectively capture one of color images or monochrome images in accordance with control information received from the image processing apparatus  120 . While color images typically convey more accurate representation of the scene depicted in an image, especially in poor lighting conditions a monochrome image may provide improved image quality and hence the possibility of selecting a device making use of the first camera  111  of desired type (e.g. color or monochrome imaging) or the possibility to select the mode of operation for the first camera  111  (e.g. color or monochrome imaging) may provide an advantage under certain operating conditions. Monochrome imaging may be provided, for example, by using a short-wave IR range of wavelengths (at approximately from 900 to 1700 nm) instead of the first range described in the foregoing. 
     Suitable cameras for serving as the first and second cameras  111 ,  112  are known in the art and a respective suitable camera unit or camera module may be applied as the first camera  111  and the second camera  112 . Consequently, details of the structure and/or operation of each of the first camera  111  and the second camera  112  are not provided in this disclosure since they are readily available for the skilled person apart from functional aspects that are relevant for describing some aspects of their usage as part of the camera assembly  110 . 
     The first camera  111  and the second camera  112  are arranged in the camera assembly  110  in fixed positions with respect to each other such that they have at least partially overlapping respective fields of view. Advantageously, the overlap is as extensive as possible in the sense that the first camera  111  and the second  112  camera enable capturing respective images that depict substantially the same scene and hence depict substantially the same real-world objects. As an example, this may be provided by arranging the first camera  111  and the second camera  112  relatively close to each other such that a first optical axis  113  of an optical system of the first camera  111  is parallel or substantially parallel with a second optical axis  114  of an optical system of the second camera  112  at a predefined distance D therefrom. The concept of ‘relatively close’ depends on the physical size of the camera assembly  110  and the physical sizes of the first camera  111  and the second camera  112  and a desired or typical distance from the camera assembly  110  to the real-world objects of interest. In an example, the first camera  111  and the second camera  112  are arranged side-by-side as close to each other as possible to ensure maximizing the overlap between respective fields of view of the first camera  111  and the second camera  112 . Consequently, as an example, the distance D between the first optical axis  113  and the second optical axis  114  may be in a range of a few centimeters. 
     Along the lines described in the foregoing, the camera assembly  110  may be operated under control of the image processing apparatus  120  in accordance with control information transferred via the communicative coupling, whereas the resulting respective images captured by the first camera  111  and the second camera  112  may be transferred from the camera assembly to the image processing apparatus  120  for analysis and/or processing therein. In particular, the camera assembly  110  may be arranged to capture and provide a respective single (still) image from the first and second cameras  111 ,  112  or it may be arranged to capture and provide a respective sequence of images (e.g. a respective video stream) from each of the first and second cameras  111 ,  112 . 
     As example, the control information transferred from the image processing apparatus  120  to the camera assembly  110  may comprise an indication or command to initiate or terminate capturing respective streams of images (e.g. video streams) using the first and second cameras  111 ,  112  and providing these streams to the image processing apparatus  120 . The indication or command to initiate the capturing and provision of the streams of images may comprise an indication of the frame rate to be applied in the streams of images provided from the camera assembly  110  to the image processing apparatus  120 . In an example, the frame rate may be a suitable value selected in a range from 5 to 240 frames per second (fps), e.g. 30 fps. In another example, the camera assembly  110  may be arranged to employ a fixed predefined frame rate (e.g. 30 fps) and hence no indication of the applicable frame rate need to be provided in the indication or command that serves to initiate capturing and provision of the streams of images. 
     In the above example the applied frame rate is implicitly assumed to be the same for the first camera  111  and the second camera  112 . In other examples, the respective frame rates of the first camera  111  and the second camera  112  may be selected or (pre)set independently of each other, such that the first and second cameras  112  may (also) employ different frame rates. 
     As another example, the control information may comprise an indication or a command to capture respective (still) images using the first camera  111  and the second camera  112  and to provide the resulting pair of images to the image processing apparatus  120 . 
     As a further example, the control information may comprise a respective indication or command for adjusting or setting one of a plurality of camera parameters accordingly, such as image size, image resolution, focal length of the camera optics, etc. The control information may enable adjusting such camera parameters of the first camera  111  and the second camera  112  independently of each other or the camera parameter adjustment may at the same time adjust respective camera parameter of the first camera  111  and the second camera  112  in a similar manner. 
     As a yet further example, the control information may further comprise an indication whether to operate the first camera  111  in a color imaging mode or in a monochrome imaging mode, provided that the employed first camera  111  provides the possibility for such a selection. The monochrome imaging mode (that may rely e.g. on short-wave IR spectrum instead of the visible color spectrum, as described in the foregoing) may be useful for providing images of improved perceivable quality in low light conditions. 
     In a yet another example, the control information may comprise an indication or a command to enable or disable operation of the first camera  111  and/or the second camera  112 . In case only one of the first and second cameras  111 ,  112  is enabled, operation of the image processing apparatus  120  results in composing an output image that is based on an image obtained from the enabled one of the first and second cameras  111 ,  112 , while a true composite image results from operation of the image processing apparatus  120  in a scenario where both the first camera  111  and the second camera  112  are simultaneously or substantially simultaneously enabled. 
     In yet another example, the camera assembly  110  further comprises at least one light source for providing illumination within the fields of view of the first and second cameras  111 ,  112  to enable capturing useable images also in poor light conditions or in a dark space. In such an arrangement the control information may comprise an indication or a command to turn the light output from the at least one light source on or off. 
     The exemplifying indications or commands for operating one or both of the first and second cameras  111 ,  112  and/or other entities of the camera assembly  110  may provided based on user input received via a user interface (UI) of a device that makes use of the image processing arrangement  100 . 
     In the foregoing and in the following, the entities arranged for capturing the respective images using visible light and IR radiation are referred to as the first camera  111  and the second camera  112 , respectively. This, however, is a choice made for editorial clarity and brevity of description and the present disclosure is not limited to implementations that make use of elements that are explicitly designated as respective camera units or camera modules and/or to approaches that make use of entities that are explicitly designated as visible light images or thermal images. In this regard, the first camera  111  generalizes into a first imaging device that comprises an array of sensors that are sensitive to visible light (e.g. an image sensor array provided as a semiconductor charge-coupled device (CCD) or as a CMOS sensor array) that enables capturing an array of pixel values that are descriptive of intensity (and possibly also the color) of visible light received at respective spatial positions of the sensor array. Along similar lines, the second camera  112  generalizes into a second imaging device that comprises an array of temperature-sensitive sensors (e.g. an array of IR sensors) that enables capturing an array of pixel values that are descriptive of temperature sensed at respective spatial positions of the sensor array. Each of the first and second imaging devices comprises respective further elements of an imaging device known in the art, such as a shutter assembly that enables suitable exposure of the sensor array and an optical system that enables focusing the incoming electromagnetic radiation at the sensor array. 
       FIG. 2  illustrates a block diagram of some logical elements of the image processing apparatus  120  according to an example. The image processing apparatus  120  comprises an image analyzer  121  and an image composer  122 . In other examples, the image processing apparatus  120  include further entities and/or the image analyzer  121  and the image composer  122  may be combined with each other and/or with one or more other entities. 
     The image analyzer  121  receives the respective images from the first camera  111  and the second camera  112  of the camera assembly  110  via the communication link  130  and carries out an image analysis described in the following via non-limiting examples. An output of the image analysis is provided for the image composer  122  that composes a composite image based on at least an image captured by one of the first and second cameras  111 ,  112  and on the output of the image analysis. The image composer  122  further passes the composite image for presentation via the UI of a device that makes use of the image processing arrangement  100 . 
     The image analyzer  121  and the image composer  122  may be arranged to jointly carry out a processing described herein as steps of a method  200  that is illustrated via a flowchart depicted in  FIG. 3 . In the following, the method  200  is described with references to deriving a single composite image based on a temporally aligned pair of images that comprises a first image captured using the first camera  111  of the camera assembly  110  and a second image captured using the second camera  112  of the camera assembly  110 . However, the method  200  readily generalizes into deriving a sequence of composite images (e.g. a video stream) based on a series of temporally aligned pairs of images that each comprise a first image taken from a sequence of first images captured using the first camera  111  of the camera assembly  110  and a second image taken from a sequence of second images captured using the second camera  112  of the camera assembly  110 . The method  200  may be varied in a plurality of ways, for example in accordance with examples pertaining to respective functionality of components of the image processing apparatus  120  provided in the foregoing and in the following. 
     The method  200  commences from obtaining a first image and a second image, as indicated in block  202 . Along the lines described in the foregoing, the first image comprises an image captured by the first camera  111  and the second image comprises as image captured by the second camera  112 . As described in the foregoing, the image processing apparatus  120  may receive one or more first images (e.g. a sequence of first images) via the communication link  130  from the first camera  111  and store the received images in a memory provided in the image processing apparatus  120 . Along similar lines, the image processing apparatus  120  may receive one or more second images (e.g. a sequence of second images) via the communication link  130  from the second camera  112  and store the received images in the memory provided in the image processing apparatus  120 . 
     As an example in this regard, the image processing apparatus  120  may be arranged to store and keep a predefined number of most recently captured first and second images in the memory, thereby deleting the oldest images from the memory as new images are received from the camera assembly  120 . In one example, the predefined number may be one, resulting in the memory of the image processing apparatus storing only the most recently captured first image and the most recently captured second image. In another example, the image processing apparatus  120  may be arranged to store and keep in the memory the most recently captured images that cover a predefined time period (e.g. a period selected from a range from a fraction of a second to a few seconds). As a further example, the image processing apparatus  120  may be arranged to store and keep all first and second images received from the camera assembly  110  in its memory (e.g. until removed in response to a user action or command). 
     According to an example, the first and second images processed as a pair by the image processing apparatus  120  are captured at the same or substantially at the same time. According to another example, a given first image is ‘paired’ with an image of the sequence of second images having its capturing time closest to that of the given first image or, the other way around, a given second image is ‘paired’ with an image of the sequence of first images having its capturing time closest to that of the given second image. Consequently, a time aligned first and second images are obtained. 
     Due to the arrangement of the first and second cameras  111 ,  112  described in the foregoing (i.e. partially overlapping respective fields of view with respective optical axes  113  and  114  in parallel at the distance D from each other), the time aligned first and second images at least partially illustrate the same real-world scene. Consequently, the first and second images have an overlapping part that in both images illustrates the same real-world objects at the location of capturing the first and second images. However, due to the different characteristics of the images, i.e. the first image comprising a visible light image depicting a scene and the second image comprising a thermal image depicting at least partially the same scene, the second image provides information that is complementary to that provided by the first image (and vice versa). 
     The method  200  further comprises identifying one or more spatial portions of the second image that represent a predefined temperature range, as indicated in block  204 . Since the second image comprises a thermal image, pixel values of the second image are directly proportional to the temperature of the real-world objects depicted therein, the second image enables locating illustrated objects based on their temperature. Herein, the identification of the one or more spatial portions that represent the predefined temperature range may include, for example, identifying one or more sets of pixel positions of the second image wherein the pixel values of the second image fall within a predefined range of pixel values that represents the predefined temperature range, thereby identifying illustrated real-world objects having their temperature within the predefined temperature range. 
     In an example, the predefined temperature range is provided as a pre-configured range of temperature values set upon manufacturing or calibrating the image capturing apparatus  100 . In another example, the predefined temperature range is selected based on user input received via a user interface (UI) arranged for controlling at least some aspects of operation of the image capturing apparatus  100 . In this regard, for example, (end points of) the predefined temperature range may be set based in user input received via the UI or (the end points of) the predefined temperature range may be selected from a plurality of predefined temperature ranges based on user input received via the UI. 
     The predefined temperature range of interest depends on the application of the image capturing apparatus  100 . A non-limiting example of a predefined temperature range of interest comprises a range of temperatures of a living human body, e.g. from 30 to 50 degrees Celsius, which may be useful for example in search and surveillance applications that aim it identifying people depicted in the first and second images. Another example concerning the temperature range of interest comprises a range of combustion temperatures of different materials that typically appear in buildings, e.g. a range of temperatures from 300 to 1025 degrees Celsius. 
     The mapping between the predefined temperature range and the corresponding range of pixel values may be provided via a predefined temperature mapping function that may be defined via a calibration procedure upon manufacturing the device making use of the image capturing apparatus  100  and/or upon configuring or re-configuring the image capturing apparatus  100  (e.g. by the user or by maintenance personnel). As an example, the calibration procedure may comprise defining a mapping between a pixel value and a corresponding temperature for a plurality of temperatures within a range from a predefined minimum temperature to a predefined maximum temperature, where the predefined temperature range of interest falls within the overall range bound by the minimum and maximum temperatures (i.e. the range of calibrated temperatures covers also temperatures below and/or above the temperature range of interest). In another example, the calibration procedure may comprise defining the mapping between a pixel value and a corresponding temperature for a plurality of temperatures within a range from a lower limit of the temperature range of interest to an upper limit of the temperature range of interest, the calibration thereby only covering the temperature range of interest. In a further example, the calibration procedure may comprise defining the mapping between a pixel value and a corresponding temperature at the lower limit of the temperature range of interest and/or at the upper limit of the temperature range of interest, the calibration thereby only covering the limit(s) of the temperature range of interest. 
     The method  200  further comprises identifying one or more spatial portions of the first image that depict the same portions of the real-world scene as illustrated in the identified in the one or more spatial portions of the second image, as indicated in block  206 . Consequently, the identified one or more spatial portions of the first image serve to depict the same real-world objects that are depicted in the identified one or more spatial portions of the second image. In this regard, since the spatial overlap between the first and second images is not complete, portions of the real-world scene depicted in some of the identified one or more spatial portions of the second image may not appear in the first image at all or may only partially appear in the first. image. 
     Since in the present example the first and second images are capturing using, respectively, the first camera  111  and the second camera  112  that have their respective optical axes  113  and  114  in parallel at the distance D from each other, there is a straightforward mapping between a pixel position of the second image that illustrates a certain point of the real-world scene and corresponding pixel position of the first image that also illustrates the certain point of the real-world scene. This relationship between the pixel position of the second image may be defined via a spatial mapping function, which in the present example involves a translation of a pixel position along an axis. As an example, assuming that optical axes  113  and  114  are at the distance D from each other along an axis x, the spatial mapping from a pixel position of the second image to the corresponding pixel position of the first image involves translation or shift in the direction of the axis x. Further considering a pixel at position (x 2 , y 2 ) in the image plane of the second image, the corresponding position (x 1 , y 1 ) in the first image may be derived, for example, using the spatial mapping function (x 1 , y 1 )=(x 2 +D, y 2 ). 
     The above example assumes the first camera  111  and the second camera  112  being arranged side-by-side, resulting in a shift of translation of a pixel position that represents the same point of the real-world scene along the horizontal axis of the image plane. Such mapping of pixel positions readily generalizes into any (predefined) relative positioning of the first and second cameras  111 ,  112  with respect to each other. Hence, the spatial mapping of a pixel position of the second image into the corresponding spatial position of the first image may be generalized into mapping a pixel position of the second image into a corresponding pixel position of the first image by translating the pixel position of the second image by a predefined amount in a predefined direction. A generalized version of the spatial mapping function may be donated, for example, as (x 1 , y 1 )=(x 2 +d x , y 2 +d y ), where (d x ) 2 +(d y ) 2 =D 2 . 
     The spatial mapping function may be defined upon manufacturing the device making use of the image capturing apparatus  100  and/or upon configuring or re-configuring the image capturing apparatus  100 . As a non-limiting example in this regard, the spatial mapping function may be found by using the first and second cameras  111 ,  112  to capture respective images of a scene that includes a single point in an uniform background and finding the shift (e.g. d x  and d y  as defined in the foregoing) that brings the point as illustrated in the second image into alignment with its illustration in the first image. 
     Consequently, the identification of the one or more spatial portions of the first image that illustrate the same portions of the real-world scene as illustrated in the identified one or more spatial portions of the second image may comprise using the spatial mapping function to find the one or more spatial portions of the first image based on the identified one or more spatial portions of the second image. In this regard, the spatial mapping function may be applied pixel-by-pixel, e.g. such that each set of pixel positions belonging to the one or more sets of pixel positions that define the identified one or more spatial portions of the second image is converted, pixel-by-pixel, into corresponding set of pixel positions of the first image via usage of the spatial mapping function, thereby obtaining the corresponding one or more sets of pixel positions of the first image that define the identified one or more spatial portions of the first image. 
     The method  200  further comprises deriving, based on the first image, a composite image wherein the identified one or more spatial portions of the first image are emphasized, as indicated in block  208 . As described in the foregoing, the identified one or more spatial portions of the first image may be defined as respective one or more sets of pixels positions of the first image. As an example in this regard, the derivation of the composite image based on the first image may comprise generating a composite image where an emphasis image is overlaid on (a copy of) the first image, wherein the emphasis image comprises respective visual indications in spatial positions that spatially correspond to the identified one or more spatial portions of the first image while other parts of the emphasis image are transparent. Consequently, the visual indications introduced via the emphasis image serve to emphasize those real-world objects depicted in the first image that were found in the second image to represent the predefined temperature range. In another example, the emphasis may be provided via directly modifying the identified one or more spatial portions of the first image to include the respective visual indications, e.g. by replacing the image content in the identified one or more spatial portions of the first image with the respective visual indications or by modifying the image content in the identified one or more spatial portions of the first image in a predefined manner. 
     In an example, a visual indication introduced into the composite image e.g. via the emphasis image or via replacement of the corresponding image content in the respective identified spatial portion of the first image may comprise introducing respective image content as a predefined color and/or as a predefined pattern. In another example, a visual indication introduced into the composite image e.g. via modification of the respective identified spatial portion of the first image may comprise adding a predefined value to each pixel value within the respective identified spatial portion of the first image or subtracting a predefined value from each pixel value within the respective identified spatial portion of the first image to provide highlighting of the respective identified spatial portion of the first image while preserving at least some characteristics of the original illustration thereof provided in the first image. 
     In a further example, a visual indication introduced into the composite image e.g. via the emphasis image or via replacement of the corresponding image content in the respective identified spatial portion of the first image may comprise outlining the respective identified spatial portion of the first image using a line or border provided using a predefined color and/or a predefined pattern, e.g. by following or substantially following the shape of the outline of the respective identified spatial portion of the first image. In a further example, a visual indication introduced into the composite image e.g. via the emphasis image or via replacement of the corresponding image content in the first image may comprise modifying the image content around the respective identified spatial portion of the first images in a predefined manner, e.g. by at least partially enclosing the respective identified spatial portion of the first image inside a frame of predefined shape (e.g. a rectangular shape), where the frame may be provided using a predefined color and/or a predefined pattern. In yet further example, a visual indication introduced into the composite image e.g. via the emphasis image or via replacement of the corresponding image content in the respective identified spatial portion of the first image may comprise the image content of the respective identified spatial portion of the second image, whereas such a visual indication may be introduced via modification of the respective identified spatial portion of the first image e.g. by adding the image content of the respective identified spatial portion of the second image to the respective identified spatial portion of the first image or by subtracting the image content of the respective identified spatial portion of the second image from the respective identified spatial portion of the first image. 
     The method  200  may further comprise providing the composite image for rendering via a display, as indicated in block  210 . The display may be provided as part of the UI arranged for controlling at least some aspects of operation of the image capturing apparatus  100 . Consequently, the composite image provides the user of the image capturing apparatus  100  with an enhanced indication of real-world objects at the location of capturing the first and second images via emphasizing the real-world objects that are found to represent the temperature range of interest. 
     As a non-limiting example of a device that makes use of the image capturing apparatus  100 ,  FIG. 4  schematically illustrates a search camera apparatus  300  according to an example. The search camera apparatus  300  comprises an elongated shaft  302  that has the camera assembly  110  arranged at or close to one end of the shaft  302  (e.g. a front end or a distal end) and a housing  304  that includes the image processing apparatus  120  and a display (possibly together with one or more other components of the UI) mounted at or close to the other end of the shaft  302  (e.g. a rear end or a proximal end). The communication link  130  may be provided, for example, via one or more electrical wires and/or via one or more optical links such as optical fibers provided within the shaft  302 . The search camera apparatus  300  may be used e.g. such that the user places the front end of the shaft  302  such that the first and second cameras  111 ,  112  of the camera assembly  110  enable view to a location that cannot be directly observed or direct observation of which involves a risk, such as interior of a collapsed building or an underwater location. After such positioning the search camera apparatus  300  the user may activate the image capturing apparatus  100  therein e.g. to obtain a composite (still) image or a sequence of composite images (e.g. a vide stream) for viewing via the display provided in the housing  304 . 
     In a variation of the search camera device  300 , instead of arranging the camera assembly  110  and the housing  304  that hosts the image processing apparatus  120  and the display in the shaft  302 , the camera assembly  110  may be arranged in a first entity and the housing  304  may be arranged in a second entity that are moveable with respect to each other, thereby enabling improved flexibility in positioning the camera assembly  110  for observance of the location of interest. In such an arrangement, the first and second entities may be coupled to each other, for example, via a flexible cable that provides the communication link  130  (e.g. one or more electrical wires and/or one or more optical links such as optical fibers) therein. In another example, there is no physical link between first and second entities but the communication link  130  is provided via usage of a suitable wireless technique known in the art. Non-limiting examples in this regard include cellular communication technologies and short-range wireless communication techniques known in the art, such the wireless local area networking according to IEEE 802.11 series of standards (e.g. Wi-Fi) or the personal area networking according to the Bluetooth™ standards, thereby enabling further enhanced flexibility in positioning the camera assembly  110  for observation of the location of interest. 
       FIG. 5  illustrates a block diagram of some components of an exemplifying apparatus  500 . The apparatus  500  may comprise further components, elements or portions that are not depicted in  FIG. 5 . The apparatus  500  may be employed e.g. in implementing the image processing apparatus  120  using a combination of hardware and software. 
     The apparatus  500  comprises a processor  516  and a memory  515  for storing data and computer program code  517 . The memory  515  and a portion of the computer program code  517  stored therein may be further arranged to, with the processor  516 , to implement at least some of the operations, procedures and/or functions described in the foregoing in context of the image processing apparatus  120 . 
     The apparatus  500  comprises a communication portion  512  for communication with other devices. The communication portion  512  comprises at least one communication apparatus that enables wired or wireless communication with other apparatuses. A communication apparatus of the communication portion  512  may also be referred to as a respective communication means. 
     The apparatus  500  may further comprise user I/O (input/output) components  518  that may be arranged, possibly together with the processor  516  and a portion of the computer program code  517 , to provide a user interface for receiving input from a user of the apparatus  500  and/or providing output to the user of the apparatus  500  to control at least some aspects of operation of the image processing apparatus  120 . The user I/O components  518  may comprise hardware components such as a display, a touchscreen, a touchpad, a mouse, a joystick, a keyboard, and/or an arrangement of one or more keys or buttons, etc. The user I/O components  518  may be also referred to as peripherals. The processor  516  may be arranged to control operation of the apparatus  500  e.g. in accordance with a portion of the computer program code  517  and possibly further in accordance with the user input received via the user I/O components  518  and/or in accordance with information received via the communication portion  512 . 
     Although the processor  516  is depicted as a single component, it may be implemented as one or more separate processing components. Similarly, although the memory  515  is depicted as a single component, it may be implemented as one or more separate components, some or all of which may be integrated/removable and/or may provide permanent/semi-permanent/dynamic/cached storage. 
     The computer program code  517  stored in the memory  515 , may comprise computer-executable instructions that control one or more aspects of operation of the apparatus  500  when loaded into the processor  516 . As an example, the computer-executable instructions may be provided as one or more sequences of one or more instructions. The processor  516  is able to load and execute the computer program code  517  by reading the one or more sequences of one or more instructions included therein from the memory  515 . The one or more sequences of one or more instructions may be configured to, when executed by the processor  516 , cause the apparatus  500  to carry out at least some of the operations, procedures and/or functions described in the foregoing in context of the image processing apparatus  120 . 
     Hence, the apparatus  500  may comprise at least one processor  516  and at least one memory  515  including the computer program code  517  for one or more programs, the at least one memory  515  and the computer program code  517  configured to, with the at least one processor  516 , cause the apparatus  500  to perform at least some of the operations, procedures and/or functions described in the foregoing in context of the image processing apparatus  120 . 
     The computer programs stored in the memory  515  may be provided e.g. as a respective computer program product comprising at least one computer-readable non-transitory medium having the computer program code  517  stored thereon, the computer program code, when executed by the apparatus  500 , causes the apparatus  500  at least to perform at least some of the operations, procedures and/or functions described in the foregoing in context of the image processing apparatus  120 . The computer-readable non-transitory medium may comprise a memory device or a record medium such as a CD-ROM, a DVD, a Blu-ray disc or another article of manufacture that tangibly embodies the computer program. As another example, the computer program may be provided as a signal configured to reliably transfer the computer program. 
     Reference(s) to a processor should not be understood to encompass only programmable processors, but also dedicated circuits such as field-programmable gate arrays (FPGA), application specific circuits (ASIC), signal processors, etc. Features described in the preceding description may be used in combinations other than the combinations explicitly described. 
     The specific examples provided in the description given above should not be construed as limiting. Therefore, the present invention is not limited merely to the embodiments described above. Features described in the preceding description may be used in combinations other than the combinations explicitly described. Although functions have been described with reference to certain features, those functions may be performable by other features whether described or not. Although features have been described with reference to certain embodiments, those features may also be present in other embodiments whether described or not.