Foreground/Background Segmentation in Digital Images

Abstract

An implementation efficient method of distinguishing between foreground and background regions of a digital image of a scene comprises capturing two images of nominally the same scene and storing the captured images in DCT-coded format, the first image being taken with the foreground more in focus than the background and the second image being taken with the background more in focus than the foreground. Regions of the first image are assigned as foreground or background according to whether the sum of selected higher order DCT coefficients decreases or increases for the equivalent regions of the second image.

1 - 23 . (canceled) 
     
     
         24 . A method of determining an orientation of an image relative to a digital image acquisition device, comprising:
 capturing two images nominally of the same scene with said digital image acquisition device;   comparing at least a portion of said two images adjacent the corresponding edges of said images to determine whether said portion comprises relatively more foreground than background; and   responsive to said portion comprising more than a threshold degree of foreground, determining that said images are oriented with said portion at their bottom.   
     
     
         25 . The method of  claim 24 , wherein said two images comprise a flash image and a non-flash image and in which said comparing comprises comparing luminance levels of pixels of said portion. 
     
     
         26 . The method of  claim 24 , wherein said two images comprise non-flash images and in which said comparing comprises comparing higher order DCT coefficients for at least one block of said portion. 
     
     
         27 . The method of  claim 24 , comprising implying an orientation of said digital image acquisition device in accordance with said image orientation. 
     
     
         28 . The method of  claim 24 , wherein said comparing comprises comparing respective portions adjacent a plurality of edges of said two images, and wherein a portion which is determined to include a greatest degree of foreground relative to other portions is deemed to be located at a bottom of said images. 
     
     
         29 . The method of  claim 28 , wherein the portion is deemed to be located at the bottom of said images based at least in part on its degree of foreground exceeding a degree of foreground for a portion adjacent an opposite edge by a given threshold. 
     
     
         30 . The method of  claim 29 , wherein said threshold is varied according to exposure level of said images or whether said images are classified as being indoor or outdoor, or combinations thereof. 
     
     
         31 . The method of  claim 28 , wherein a portion is deemed to be located at the bottom of said images when its degree of foreground exceeds a degree of foreground for a portion adjacent at least an adjacent edge, and a degree of foreground for a portion adjacent said adjacent edge exceeds a degree of foreground for a portion adjacent an opposite edge. 
     
     
         32 . A digital image acquisition system having no photographic film comprising:
 means for capturing two images nominally of the same scene;   means for comparing at least a portion of said two images adjacent the corresponding edges of said images to determine whether said portion comprises relatively more foreground than background; and   means, responsive to said portion comprising more than a threshold degree of foreground, for determining that said images are oriented with said portion at their bottom.   
     
     
         33 . One or more processor readable storage devices having processor readable code embodied thereon, said processor readable code for programming one or more processors to perform a method of determining an orientation of an image relative to a digital image acquisition device, the method comprising:
 capturing two images nominally of the same scene with said digital image acquisition device;   comparing at least a portion of said two images adjacent the corresponding edges of said images to determine whether said portion comprises relatively more foreground than background; and   responsive to said portion comprising more than a threshold degree of foreground, determining that said images are oriented with said portion at their bottom.   
     
     
         34 . The one or more storage devices of  claim 33 , wherein said two images comprise a flash image and a non-flash image and in which said comparing comprises comparing luminance levels of pixels of said portion. 
     
     
         35 . The one or more storage devices of  claim 33 , wherein said two images comprise non-flash images and in which said comparing comprises comparing higher order DCT coefficients for at least one block of said portion. 
     
     
         36 . The one or more storage devices of  claim 33 , comprising implying an orientation of said digital image acquisition device in accordance with said image orientation. 
     
     
         37 . The one or more storage devices of  claim 33 , wherein said comparing comprises comparing respective portions adjacent a plurality of edges of said two images, and wherein a portion which is determined to include a greatest degree of foreground relative to other portions is deemed to be located at a bottom of said images. 
     
     
         38 . The one or more storage devices of  claim 37 , wherein the portion is deemed to be located at the bottom of said images based at least in part on its degree of foreground exceeding a degree of foreground for a portion adjacent an opposite edge by a given threshold. 
     
     
         39 . The one or more storage devices of  claim 38 , wherein said threshold is varied according to exposure level of said images or whether said images are classified as being indoor or outdoor, or combinations thereof. 
     
     
         40 . The one or more storage devices of  claim 37 , wherein a portion is deemed to be located at the bottom of said images when its degree of foreground exceeds a degree of foreground for a portion adjacent at least an adjacent edge, and a degree of foreground for a portion adjacent said adjacent edge exceeds a degree of foreground for a portion adjacent an opposite edge. 
     
     
         41 . A digital image acquisition device, comprising:
 a lens and image sensor for capturing digital images;   a processor; and   one or more processor readable storage devices having processor readable code embodied thereon, said processor readable code for programming one or more processors to perform a method of determining an orientation of an image relative to a digital image acquisition device, the method comprising:
 capturing two images nominally of the same scene with said digital image acquisition device; 
 comparing at least a portion of said two images adjacent the corresponding edges of said images to determine whether said portion comprises relatively more foreground than background; and 
 responsive to said portion comprising more than a threshold degree of foreground, determining that said images are oriented with said portion at their bottom. 
   
     
     
         42 . The device of  claim 41 , wherein said two images comprise a flash image and a non-flash image and in which said comparing comprises comparing luminance levels of pixels of said portion. 
     
     
         43 . The device of  claim 41 , wherein said two images comprise non-flash images and in which said comparing comprises comparing higher order DCT coefficients for at least one block of said portion. 
     
     
         44 . The device of  claim 41 , wherein the method further comprises implying an orientation of said digital image acquisition device in accordance with said image orientation. 
     
     
         45 . The device of  claim 41 , wherein said comparing comprises comparing respective portions adjacent a plurality of edges of said two images, and wherein a portion which is determined to include a greatest degree of foreground relative to other portions is deemed to be located at a bottom of said images. 
     
     
         46 . The device of  claim 45 , wherein the portion is deemed to be located at the bottom of said images based at least in part on its degree of foreground exceeding a degree of foreground for a portion adjacent an opposite edge by a given threshold. 
     
     
         47 . The device of  claim 46 , wherein said threshold is varied according to exposure level of said images or whether said images are classified as being indoor or outdoor, or combinations thereof. 
     
     
         48 . The device of  claim 46 , wherein a portion is deemed to be located at the bottom of said images when its degree of foreground exceeds a degree of foreground for a portion adjacent at least an adjacent edge, and a degree of foreground for a portion adjacent said adjacent edge exceeds a degree of foreground for a portion adjacent an opposite edge.