Patent Publication Number: US-2017372495-A1

Title: Methods and systems for color processing of digital images

Description:
TECHNICAL FIELD 
     The present disclosure generally relates to methods and systems for color processing of digital images and, more particularly, to methods and systems that color and re-color digital images. 
     BACKGROUND 
     Conventional processes for colorization of grayscale images and re-coloring of color images can produce visual artifacts in the resulting image. For example, conventional colorizing processes, particularly automatic color image processing/mapping methods, such as color transfer and color harmonization, can produce color inconsistency in areas where the color and/or luminance values change smoothly in the original image. Thus, strong artificial color edges that do not exist in the original image may be created in the resulting image. In addition, other types of image processing that do not modify color directly can also produce visual artifacts that affect the color of an image. 
     SUMMARY 
     Described herein are various systems and methods for digital image coloring and re-coloring that may eliminate or reduce visual artifacts in images in comparison to conventional colorization, re-coloring, or other image processing that can affect image color. In various embodiments, a first image (e.g., a grayscale image or color image) can be segmented to obtain segmented image regions. A morphological skeleton can be determined for each segmented image region, and color can be associated with each morphological skeleton. If the first image is a color image, the color associated with a morphological skeleton can be based on, for example, a most frequent color of the corresponding segmented image region in the first image. If the first image is a grayscale image, the color associated with a morphological skeleton can be based on, for example, a user-input color for each segmented image region. 
     Each color can be diffused from the associated morphological skeleton to obtain color information for a second image, and the second image can be obtained based on the color information. For example, in various embodiments, the second image can be obtained directly from the color diffusion process. In other embodiments, other processing, such as gamma correction, color saturation adjustment, etc., can be applied after the diffusion process to generate the second image. In this way, for example, better resulting color images (i.e., the second image) may be produced because morphological skeletons can span segmented image regions well. As a result, color can be evenly diffused throughout the segmented image regions, which may reduce undesirable desaturation that can occur near the edges of the regions 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a block diagram of an image collection device according to various embodiments. 
         FIG. 2  is a flowchart of an example of a method according to various embodiments. 
         FIG. 3  is an illustration of an input greyscale image to be colorized according to various embodiments. 
         FIG. 4  illustrates a segmented image that includes segmented image regions resulting from segmenting a greyscale image according to various embodiments. 
         FIG. 5  is a conceptual illustration showing a segmented image including a morphological skeleton determined for each segmented image region according to various embodiments. 
         FIG. 6  is a conceptual illustration showing color-seeded morphological skeletons according to various embodiments. 
         FIG. 7  is a conceptual illustration showing color diffusion from color-seeded morphological skeletons according to various embodiments. 
         FIG. 8  is a conceptual illustration of a colorized image of an input grayscale image according to various embodiments. 
         FIG. 9  is a flowchart of an example of another method according to various embodiments. 
         FIGS. 10A-B  show a conceptual illustration of an example of an implementation of the method of  FIG. 9  to re-color a colorized image of an original grayscale image according to various embodiments. 
         FIG. 11  illustrates another example of an apparatus according to various embodiments. 
     
    
    
     It should be understood that the drawings are for purposes of illustrating the concepts of the disclosure and are not necessarily the only possible configurations for illustrating the disclosure. 
     DETAILED DESCRIPTION 
     Processes for colorization of grayscale images, re-coloring of color images, and other types of image processing can produce visual artifacts in the color of resulting images. Described herein are various systems and methods for colorizing and re-coloring that may produce resulting images with fewer or no visual artifacts. In various embodiments, the techniques may be used as stand-alone methods for colorization and/or re-coloring digital images. In various embodiments, the techniques can be implemented as post-processing to help correct visual artifacts that can result from other colorizing or re-coloring processes. Some conventional methods might, for example, produce color inconsistency in areas where the color and/or luminance values change smoothly in the original image. Thus, strong artificial color edges that do not exist in the original image may be created in the resulting image. In this regard, various embodiments can be implemented as a regularization method that can be seen as a post-processing technique for improving the visual quality of any color image processing method. Algorithms, such as color transfer, color harmonization, etc., may be used first, and processes implementing the techniques described herein can be applied afterwards as post-processing. 
     The techniques described herein may be implemented in any kind of device that can perform image processing, such as a personal computer executing image processing software, an image collection device, e.g., a camera, video camera, etc., that includes image processing functionality, a smart phone, a tablet computer, etc. For example,  FIG. 1  is a block diagram of an image collection device  100  according to various embodiments. In  FIG. 1 , light  102  reflected from a scene can be collected and focused by optical elements  104 . The focused light  106  can be projected onto a detector  108 , which may be, for example, a charge coupled device or other kind of light detection system. Focused light  106  can be converted by detector  108  into an electrical signal, and can be then transferred over signal lines  110  to a detector controller  112 . In detector controller  112 , the individual signals from detector  108  can be converted into a digital image. The digital image may then be transferred by a processor  114  over a bus  116  to a random access memory (RAM)  118  for further processing. RAM  118  may be a dynamic RAM (DRAM), a static RAM (SRAM), a flash memory module, or other kind of computer memory. 
     Optical elements  104  may be connected to the bus  116  to allow optical elements  104  to be controlled by processor  114 . For example, processor  114  may adjust the focus, the stop, or other properties of optical elements  104  through bus  116 . 
     Processor  114  may be controlled by image collection and processing programs contained in a read only memory (ROM)  120  that can be accessible from bus  116 . The programs do not have to be in a ROM, but may be contained in any type of long-term memory, such as a disk drive, a flash card, or an electrically erasable programmable read only memory (EEPROM), among others. Generally, the programs in ROM  120  may include the image coloring, re-coloring, and color correction procedures discussed with respect to  FIGS. 2-10 . 
     The digital image may be stored before or after processing in a separate digital image storage  122 , such as a digital video tape, a recordable optical disk, a hard drive, and the like. Digital image storage  122  may also be combined with the program storage. For example, a disk drive may be used both to store both programs and digital images. 
     The images may be displayed on a display unit  124  that may be connected to bus  116 . Controls  126  may also be connected to bus  116  to control the collection and processing of the images by processor  114 . Such controls  126  may include keypads, selection knobs, and separate buttons for functions such as zooming, focusing, starting the collection of images, etc. 
     Images may be transferred from image collection device  100  through a network interface controller (NIC)  128  that may be connected to bus  116 . NIC  128  may be connected to an external local area network (LAN)  130 , which may be used to transfer the images to an external device  132  located on LAN  130 . 
     The arrangement of the functional blocks presented above is only one possible arrangement, and any number of other arrangements may be used. For example, NIC  128  may be directly coupled to an area of RAM  118  to allow direct memory access, or DMA, transfers to occur directly to and from RAM  118  of the digital collection device. This may accelerate data transfers when a large amount of data is involved, such as in a high definition digital video camera. Further, in other arrangements controls  126  and display  128  may be combined into a single unit. In yet other combinations, display  128  may be directly connected to detector controller  112  to off-load the display function from processor  114 . 
       FIG. 2  is a flowchart of an example of a method according to various embodiments. In some embodiments, the method may be implemented to colorize grayscale images. In some embodiments, the method may be implemented to re-color a color image. Likewise, in some embodiments the method may be used as a post-processing step to help correct visual artifacts that can result from other colorizing or re-coloring processes.  FIGS. 3-8  are conceptual drawings to illustrate an example of an implementation of the method of  FIG. 2  to colorize grayscale images according to various embodiments. During the description of the method of  FIG. 2  below,  FIGS. 3-8  will be referenced in order to illustrate how the method of  FIG. 2  can be implemented according to one particular embodiment. 
     Referring to  FIG. 2 , an image to be processed (e.g., a grayscale image to be colorized or a color image to be re-colored) can be obtained, for example, from the memory of an image processing device, such as digital image storage  122  of image collection device  100 . For example,  FIG. 3  is an illustration of an input greyscale image  300  to be colorized. The image can be segmented ( 201 ) to obtain segmented image regions. For example,  FIG. 4  illustrates a segmented image  400  that includes segmented image regions  401  resulting from segmenting greyscale image  300 . 
     Segmentation can include superpixel segmentation, which can estimate consistent regions by grouping pixels into perceptually meaningful regions. The pixel groupings can capture image redundancy, provide a convenient primitive from which to compute image features, and reduce the complexity of subsequent image processing tasks. In some cases a superpixel algorithm, by itself, may create over-segmentation or under-segmentation, which may lead to additional color artifacts. In various embodiments, segmentation can include a modified superpixel segmentation that may mitigate creation of additional artifacts. A modified superpixel segmentation can include over-segmenting the image and then merging superpixels that are spatially close and have similar statistics (e.g., similar luminance mean and variance). For example, after a superpixel algorithm is applied, adjacent superpixels S 1  and S 2  can be merged if: 
       √{square root over ((μ S2 −μ S1 )+(σ S2 −σ S1 ) 2 )}&lt; T   (1)
 
     Where μ S2 , μ S1  and σ S2 , σ S1  are the mean and variance of the considered superpixels, respectively. T is a threshold, which can be set to 2.5. 
     It should be noted that superpixel segmentation is merely one type of segmentation that can be used. However, other methods for segmenting images can be implemented, as one skilled in the art will readily understand. In various embodiments, segmentation can be based on luminance information, for example, luminance components of an input image to be colorized such as grayscale image  300 . In some embodiments in which a color image is to be re-colored (e.g., to remove artifacts caused by the colorization process), segmentation can be based on luminance information of the color image itself, while in other embodiments, segmentation can be based on luminance information of the original grayscale image that was colorized to result in the colorized image (if luminance information of the original grayscale image is obtained). 
     In various embodiments, the methods of  FIG. 2  and  FIGS. 3-8  can be applied to grayscale and color images regardless of any previous image processing that the images may have undergone, i.e., independent of any previous image processing. In various embodiments, the methods may be used in post-processing of images to correct artifacts that can result from previous image processing. 
     After the image has been segmented, a morphological skeleton (e.g., a medial axis representation) can be determined ( 202 ) for each segmented image region. In other words, the segmented image regions can provide a basis for determining morphological skeletons. The morphological skeletons can be used as starting locations for color in a color diffusion process. Morphological skeletons may provide better color diffusion results in comparison to using other types of strokes or using points for the starting locations. In particular, morphological skeletons may span the segmented image regions better, such that color can be more evenly diffused throughout the segmented image regions. This may reduce undesirable desaturation that can occur near the edges of the segmented image regions, particularly when a single point within each segmented image region is used as the starting location. 
       FIG. 5  is a conceptual illustration  500  showing a segmented image including a morphological skeleton  501  determined for each segmented image region  401 . 
     A color can be associated ( 203 ) with each morphological skeleton. In other words, each morphological skeleton can be seeded with color. In various embodiments, the color associated with each morphological skeleton can be based on, for example, an input color image to be re-colored, a color template image, user input, etc. 
     As described above, the segmented image regions can provide a basis for determining morphological skeletons. In various embodiments, the segmented image regions also can provide a basis for determining the colors to be associated with the morphological skeletons. For example, in various embodiments directed to re-coloring an input color image, the color to associate with each morphological skeleton can be determined in a variety of ways. For example, in some embodiments the color associated with each morphological skeleton can be based on the color in the segmented image region in the input color image. For example, associating color with each morphological skeleton can include determining a most frequent color of the segmented image region in the input color image. In various embodiments, the color associated with each morphological skeleton can be determined based on a mean color, a median color, etc., of the segmented image region in the input color image. Other ways to determine the color to associate with each morphological skeleton can include, for example, clustering the hues in the input color image and assigning a closest hue to each segmented image region, using one or more of various voting schemes, etc., as one skilled in the art will readily understand. 
     In various embodiments directed to colorizing an input grayscale image, the color to associate with each morphological skeleton can be determined in a variety of ways. For example, in some embodiments the input grayscale image showing the boundaries of the segmented image regions can be displayed to a user, and the user can input a desired color for each segmented image region. The desired colors can be associated with the corresponding morphological skeletons. In other embodiments, a color image may be used as a template for the determining colors associated with morphological skeletons. For example, the color template image may be segmented as well, and the segmented image regions of the color template image may be matched with the segmented image regions of the input greyscale image, e.g., based on texture-mapping, etc. Colors can be associated with the morphological skeletons based on, for example, a most frequent color, a mean color, a median color, etc., of the segmented image region in the color template image that matches the segmented image region in the input grayscale image. 
       FIG. 6  is a conceptual illustration  600  showing color-seeded morphological skeletons  601 , which are obtained by associating color with morphological skeletons  501 . 
     Color can be diffused ( 204 ) from each morphological skeleton. In various embodiments, color diffusion from morphological skeletons can be based, for example, on Levin&#39;s algorithm, which can take into account the luminance of nearby pixels, such that if the luminance is similar the color is diffused to the nearby pixel, and if the luminance is not similar the color is not diffused. At any given pixel, color diffusion from one morphological skeleton potentially can overlap with color diffusion from one or more other morphological skeletons. In these cases, various methods can be used to determine the final color assigned to the pixel. In various embodiments, for example, a confidence value can be determined for the diffused color from each morphological skeleton. The confidence values can be compared, and the diffused color with the highest confidence value can be assigned to the pixel. In other embodiments, a weight can be determined for the diffused color from each morphological skeleton, and the diffused colors can be combined based on the weights to obtain a final color value assigned to the pixel. In various embodiments, weights and/or confidence levels can be based on factors including, for example, distance from the morphological skeleton, morphological skeleton size, differences between the overlapping diffused colors, etc. Other methods of diffusing color may be used, such as methods that take into account texture, boundaries, etc., such as one skilled in the art will readily understand. 
       FIG. 7  is a conceptual illustration  700  showing color diffusion from color-seeded morphological skeletons  601 . The color diffusion is illustrated by small arrows extending from the color-seeded morphological skeletons. For the sake of clarity, color diffusion is illustrated for only some of the color-seeded morphological skeletons, but it should be understood that color is diffused from all of the color-seeded morphological skeletons. 
     A color image can be obtained ( 205 ) based on the diffused color. For example, in various embodiments the color image can be the direct result of the color diffusion. In some embodiments, other processing can be applied to the result of the color diffusion to obtain a final color image. Other processing can include, for example, gamma correction, color saturation adjustment, etc.  FIG. 8  is a conceptual illustration of a colorized image  800  of input grayscale image  300  that can result from the color diffusion of color-seeded morphological skeletons  601 . 
       FIG. 9  is a flowchart of an example of another method according to various embodiments. The method may be implemented to re-color a color image, for example, as a post-processing step to help correct visual artifacts that can result from other colorizing or re-coloring processes. In this regard, the method may help reduce or eliminate typical artifacts caused by automatic color image processing/mapping methods, such as color transfer, color harmonization, colorization of greyscale pictures, etc. In particular, some conventional image processing methods might produce color inconsistency in areas where the color and/or luminance values change smoothly in the original picture. For example, some conventional colorization methods can create spatial irregularities, strong artificial color edges, etc., that are not present in the original image. The method of  FIG. 9  may be viewed as a regularization method that can be implemented as a post-processing for improving the visual quality of any color image processing method. 
       FIGS. 10A-B  show a conceptual illustration of an example of an implementation of the method of  FIG. 9  to re-color a colorized image of an original grayscale image. During the description of the method of  FIG. 9  below,  FIGS. 10A-B  will be referenced in order to illustrate how the method of  FIG. 9  can be implemented according to one particular embodiment. 
     Referring to  FIG. 9 , luminance information of an original image can be obtained ( 901 ). The luminance information can include, for example, luminance components of the original image, such as values of a luminance channel at each pixel. Color information of a modified image can be obtained ( 902 ). The color information can include, for example, color components of the modified image, such as values of color channels at each pixel. The modified image can be an image resulting from image processing of the original image. In various embodiments, the modified image can be a colorized version of an original grayscale image. For example, in the implementation shown in  FIGS. 10A-B , an original grayscale image  1000  has been colorized, for example using a conventional colorization method, resulting in a colorized image  1001 . In some embodiments, the modified image can be a re-colored version of an original color image. 
     Segmented image regions can be determined ( 903 ) based on the luminance information of the original image. As in the method described above with respect to the method of  FIG. 2 , segmentation can include superpixel segmentation. In some cases superpixel algorithm, by itself, may create over-segmentation or under-segmentation, which may lead to additional color artifacts. In various embodiments, segmentation can include a modified superpixel segmentation, which can include over-segmenting the image and then merging superpixels that are spatially close and have similar statistics (e.g., similar luminance mean and variance). For example, after a superpixel algorithm is applied, adjacent superpixels S 1  and S 2  can be merged based on Equation (1) above, for example. Although superpixel segmentation is described herein as one method of segmentation, other methods for segmenting images can be implemented, as one skilled in the art will readily understand. 
       FIG. 10A  shows luminance information  1003  can be obtained from original grayscale image  1000 , and segmented image regions  1005  can be determined based on the luminance information. 
     A color seed can be determined ( 904 ) for each segmented image region based on the color information of the modified image. In various embodiments, determining a color seed for each segmented image region can include determining a starting location, such as a morphological skeleton, a point, etc., corresponding to the segmented image region and associating color with the morphological skeleton, where the associated color is based on the color information of the modified image. Techniques described above with respect to the method of  FIG. 2  can be applied, for example, to determine morphological skeletons and seed the morphological skeletons with color, as one skilled in the art will readily understand. Similar techniques can be used to determine points or other shapes as starting locations, and to seed the starting locations with color. For example, each starting location can be determined as a center point of each segmented image region. 
       FIG. 10A  shows a starting location  1007  determined for each segmented image region. For the sake of clarity, starting locations  1007  are shown as dots in  FIG. 10A . However, it should be understood that the starting locations can be, e.g., points, morphological skeletons, other strokes, etc. Color information  1009  can be obtained from colorized image  1001 , and starting locations  1007  can be seeded with color based on the color information to obtain color seeds  1011 . 
     It should be noted that the segmented image regions can provide a basis for determining the colors of the color seeds. For example, in various embodiments the color associated with each morphological skeleton, point, etc., can be based on the color of the segmented image region in the modified image, e.g., the colorized image in the example of  FIGS. 10A-10B . For example, associating color with each morphological skeleton, point, etc., can include determining a most frequent color of the segmented image region in the modified image. In various embodiments, the color associated with each morphological skeleton, point, etc., can be determined based on a mean color, a median color, etc., of the segmented image region in the modified image. Other ways to determine the color to associate with each morphological skeleton, point, etc., can include, for example, clustering the hues in the modified image and assigning a closest hue to each segmented image region, using one or more of various voting schemes, etc., as one skilled in the art will readily understand. 
     A re-colored image can be determined ( 905 ) based on diffusing the color seeds. As described above with respect to  FIG. 2 , in various embodiments color diffusion can be based, for example, on Levin&#39;s algorithm, which can take into account the luminance of nearby pixels, such that if the luminance is similar the color is diffused to the nearby pixel, and if the luminance is not similar the color is not diffused. In this case, the luminance of each pixel can be based on the luminance information, such as luminance components, of pixels in the original image. Other methods of diffusing color may be used, such as methods that take into account texture, boundaries, etc., such as one skilled in the art will readily understand. Color components can be determined based on diffusing the color seeds, and the re-colored image be determined by combining the color components with the luminance components of the original image. 
     In  FIG. 10B , color diffusion  1013  from seeds is illustrated by small arrows extending from color seeds  1011 . Re-colored image  1015  can be determined based on color diffusion  1013 . As in the method described above with respect to  FIG. 2 , in various embodiments the re-colored image can be the direct result of the color diffusion. In some embodiments, other processing can be applied to the result of the color diffusion to obtain a final re-colored image. Other processing can include, for example, gamma correction, color saturation adjustment, etc. 
       FIG. 11  illustrates another example of an apparatus according to various embodiments.  FIG. 11  is a block diagram of an apparatus  1100  for implementing various techniques described above for coloring and re-coloring digital images. Apparatus  1100  may be implemented, for example, as a general-purpose computing platform. 
     Apparatus  1100  can include a processor  1110  for executing the computer-executable programs that perform various techniques described above. The programs may be stored in a memory  1120 , which may also store image data. A bus  1130  can connect processor  1110  and memory  1120  to each other and to other components of apparatus  1100 . In some embodiments, apparatus  1100  may include multiple processors or processors with multiple processing cores, which may execute various parts of programs in parallel. 
     A mass storage device  1140  can be connected to bus  1130  via a disk controller  1150 . Mass storage device  1140  may contain image or video data, as well as an operating system, other programs, other data, etc. Disk controller  1150  may operate according to Serial Advanced Technology Advancement (SATA), Small Computer System Interface (SCSI), or other standards, and may provide connection to multiple mass storage devices. 
     A video display  1160  can be connected to bus  1130  via a video controller  1170 . Video controller  1170  may provide its own memory and graphics-processing capability for use in implementing or accelerating certain aspects of the colorization, re-colorization, or color correction processes, as well as for providing the functions of image and UI display. 
     An input device  1180  can be connected to bus  1130  via an input/output (I/O) controller  1190 . I/O controller  1190  may utilize one or more of USB, IEEE 1394a, or other standards. Multiple input devices may be connected, such as keyboards, mice, and trackpads. Image and video capture devices may also be connected to the system through I/O controller  1190  or additional I/O controllers implementing other I/O standards. Networking functionality may be provided by I/O controller  1190  or a separate I/O controller. 
     Thus, various embodiments can include a system including a processor and a memory storing instructions configured to cause the processor to segment a first image to obtain segmented image regions, determine a morphological skeleton for each segmented image region, associate color with each morphological skeleton, diffuse each color from the associated morphological skeleton to obtain color information for a second image, and obtain the second image based on the color information. In various embodiments, segmenting the first image is based on luminance information of the first image. In various embodiments, segmenting the first image includes performing superpixel segmentation. In various embodiments, segmenting the first image further includes merging two or more superpixels, the superpixels resulting from performing the superpixel segmentation. In various embodiments, associating color with each morphological skeleton includes determining a color based on the corresponding segmented image region in the first image. In various embodiments, the first image is a color image, and determining the color based on the corresponding segmented image region includes determining a most frequent color of the segmented image region in the first image, and associating color with each morphological skeleton includes associating the most frequent color with the morphological skeleton. In various embodiments, the first image is a grayscale image, and determining the color based on the corresponding segmented image region includes displaying boundaries of the segmented image region and receiving a user-input color for the segmented image region, and associating color with each morphological skeleton includes associating the user-input color with the morphological skeleton. In various embodiments, associating color with each morphological skeleton includes determining a color based on a third image, the third image being a color image. In various embodiments, diffusing each color from the associated morphological skeleton includes diffusing each color based on luminance information of the first image. 
     Various embodiments can include a method including segmenting a first image to obtain segmented image regions, determining a morphological skeleton for each segmented image region, associating color with each morphological skeleton, diffusing each color from the associated morphological skeleton to obtain color information for a second image, and obtaining the second image based on the color information. In various embodiments, segmenting the first image is based on luminance information of the first image. In various embodiments, segmenting the first image includes performing superpixel segmentation. In various embodiments, segmenting the first image further includes merging two or more superpixels, the superpixels resulting from performing the superpixel segmentation. In various embodiments, associating color with each morphological skeleton includes determining a color based on the corresponding segmented image region in the first image. In various embodiments, the first image is a color image, and determining the color based on the corresponding segmented image region includes determining a most frequent color of the segmented image region in the first image, and associating color with each morphological skeleton includes associating the most frequent color with the morphological skeleton. In various embodiments, the first image is a grayscale image, and determining the color based on the corresponding segmented image region includes displaying boundaries of the segmented image region and receiving a user-input color for the segmented image region, and associating color with each morphological skeleton includes associating the user-input color with the morphological skeleton. In various embodiments, associating color with each morphological skeleton includes determining a color based on a third image, the third image being a color image. In various embodiments, diffusing each color from the associated morphological skeleton includes diffusing each color based on luminance information of the first image. 
     Various embodiments can include a non-transitory computer-readable medium storing computer-executable instructions executable to perform a method including segmenting a first image to obtain segmented image regions, determining a morphological skeleton for each segmented image region, associating color with each morphological skeleton, diffusing each color from the associated morphological skeleton to obtain color information for a second image, and obtaining the second image based on the color information. In various embodiments, segmenting the first image is based on luminance information of the first image. In various embodiments, segmenting the first image includes performing superpixel segmentation. In various embodiments, segmenting the first image further includes merging two or more superpixels, the superpixels resulting from performing the superpixel segmentation. In various embodiments, associating color with each morphological skeleton includes determining a color based on the corresponding segmented image region in the first image. In various embodiments, the first image is a color image, and determining the color based on the corresponding segmented image region includes determining a most frequent color of the segmented image region in the first image, and associating color with each morphological skeleton includes associating the most frequent color with the morphological skeleton. In various embodiments, the first image is a grayscale image, and determining the color based on the corresponding segmented image region includes displaying boundaries of the segmented image region and receiving a user-input color for the segmented image region, and associating color with each morphological skeleton includes associating the user-input color with the morphological skeleton. In various embodiments, associating color with each morphological skeleton includes determining a color based on a third image, the third image being a color image. In various embodiments, diffusing each color from the associated morphological skeleton includes diffusing each color based on luminance information of the first image. 
     It will be recognized by one skilled in the art that various aspects of the methods of the present disclosure may be executed in parallel on multiple systems to provide faster processing. For instance, in the case of processing a video file, frames may be divided among tens or hundreds of computing systems to provide parallel processing. Particular components, such as video display  1160 , may be omitted in some systems in some operating environments. Furthermore, multiple systems may utilize shared storage accessed via an I/O bus or via a network. 
     It will be further recognized by one skilled in the art that apparatus  1100  may be implemented within an image capture device such as a digital still camera or digital video camera. Various techniques disclosed herein may be implemented by apparatus  1100  at the time of image capture to color, re-color, or perform color correction. 
     It should also be appreciated that although various examples of various embodiments have been shown and described in detail herein, those skilled in the art can readily devise other varied embodiments that still remain within the scope of this disclosure. 
     All examples and conditional language recited herein are intended for instructional purposes to aid the reader in understanding the principles of the disclosure and the concepts contributed by the inventor to furthering the art, and are to be construed as being without limitation to such specifically recited examples and conditions. 
     Moreover, all statements herein reciting principles, aspects, and embodiments of the disclosure, as well as specific examples thereof, are intended to encompass both structural and functional equivalents thereof. Additionally, it is intended that such equivalents include both currently known equivalents as well as equivalents developed in the future, i.e., any elements developed that perform the same function, regardless of structure. 
     Thus, for example, it will be appreciated by those skilled in the art that the block diagrams presented herein represent conceptual views of illustrative circuitry, electrical components, optical components, etc., embodying the principles of the disclosure. Similarly, it will be appreciated that any flow charts, flow diagrams, state transition diagrams, pseudocode, and the like represent various processes which may be substantially represented in computer readable media and so executed by a computer or processor, whether or not such computer or processor is explicitly shown. 
     The functions of the various elements shown in the figures may be provided through the use of dedicated hardware as well as hardware capable of executing software in association with appropriate software. When provided by a processor, the functions may be provided by a single dedicated processor, by a single shared processor, or by a plurality of individual processors, some of which may be shared. Moreover, explicit use of the term “processor” or “controller” should not be construed to refer exclusively to hardware capable of executing software, and may implicitly include, without limitation, digital signal processor (“DSP”) hardware, read only memory (“ROM”) for storing software, random access memory (“RAM”), and nonvolatile storage. 
     Other hardware, conventional and/or custom, may also be included. Similarly, any switches shown in the figures are conceptual only. Their function may be carried out through the operation of program logic, through dedicated logic, through the interaction of program control and dedicated logic, or even manually, the particular technique being selectable by the implementer as more specifically understood from the context. 
     In the claims hereof, any element expressed as a means for performing a specified function is intended to encompass any way of performing that function including, for example, a combination of circuit elements that performs that function, software in any form, including, therefore, firmware, microcode or the like, combined with appropriate circuitry for executing that software to perform the function, etc. The disclosure as defined by such claims resides in the fact that the functionalities provided by the various recited means are combined and brought together in the manner which the claims call for. It is thus regarded that any means that can provide those functionalities are equivalent to those shown herein.