Method and device for encoding and decoding a stack of images, and corresponding computer program product

Abstract

Encoding or decoding a stack of images of a same scene focused at different focalization distances from one image to another can involve encoding or decoding information representing an image of the stack of images, where the image meets an image sharpness criterion, reconstructing the image into a reconstructed image, and encoding or decoding at least one other image of the stack of images by prediction from at least the reconstructed image.

1 . A method comprising
 encoding a stack of images of a same scene focused at a different focalization distances from one image to another, wherein the encoding comprises:   encoding information representing an image of the stack of images, the image being selected in the stack of images according to an image sharpness criterion, and reconstructing the image into a reconstructed image;   encoding at least one other image of the stack of images by prediction from at least the reconstructed image.   
     
     
         2 . The method of  claim 1 , wherein the image sharpness criterion corresponds to a number of pixels in focus in an image. 
     
     
         3 . The method of  claim 2 , wherein the selected image in the stack of images is an image having a highest number of pixels in focus among the images included in the stack of images. 
     
     
         4 . The method of  claim 3 , wherein the image in the stack of images having the highest number of pixels in focus is an all-in-focus image. 
     
     
         5 . The method of  claim 1 , wherein encoding the at least one other image of the stack of images by prediction from at least the reconstructed image comprises encoding, for at least a pixel of the at least one other image, a value from a corresponding pixel collocated in the reconstructed image and from a blurring function depending on a depth position associated with the at least one other image to encode. 
     
     
         6 . The method of  claim 1 , wherein the stack of images is one of a group of stacks of images captured with different viewing angles, the stacks of images included in the group of stacks of images being ordered according to an orientation order of their respective viewing angles, and wherein the method further comprises:
 determining an inter-stack image encoding order from the orientation order and from a reference viewing angle corresponding to a viewing angle of the stack of images,   encoding at least one pixel of an image of at least one other stack of images included in the group of stacks of images processed according to the inter-stack image encoding order from the reconstructed image, the image of the at least one other focal stack being designated a reference image selected according to the image sharpness criterion.   
     
     
         7 . The method of  claim 6 , wherein the pixel of the reference image is encoded from the reconstructed image of the stack of images, captured from the reference viewing angle, and from information representing a disparity between the reference image and the reconstructed image of the stack of images. 
     
     
         8 . The method of  claim 6 , wherein the value of each pixel of the reference image, captured from a viewing angle different from the reference viewing angle, is encoded from the reconstructed image of the stack of images, captured with the reference viewing angle, and from a layered depth image of a scene associated to the group of stacks of images. 
     
     
         9 . The method of  claim 6 , wherein the group of stacks of images is captured at a reference instant t 0 , and is a part of a sequence of groups of stacks of images further comprising at least one other group of stacks of images captured at an instant t, and wherein the method further comprises encoding at least one pixel of a reference image of a stack of images, captured with the reference viewing angle, of the at least one other group of stacks of images, captured at an instant t, of the sequence of groups of stacks of images, by using a temporal prediction performed from the reconstructed image of the stack of images captured at the reference instant t 0 . 
     
     
         10 . The method of  claim 4 , further comprising
 combining at least the encoded information representing the image of the stack of images selected according to the image sharpness criterion and the at least one other encoded image of the stack of images into a signal representing the stack of images; and   inserting a map to reconstruct the all-in-focus image of the stack of images in the signal representing the stack of images.   
     
     
         11 . A method comprising:
 decoding a stack of images of a same scene focused at a different focalization distances from one image to another, wherein the decoding comprises
 decoding information representing an image of the stack of images, the image fulfilling an image sharpness criterion, 
 reconstructing at least one other image of the stack of images by prediction from at least the decoded image. 
   
     
     
         12 . The method of  claim 11 , wherein the image sharpness criterion corresponds to a number of pixels in focus in an image. 
     
     
         13 . The method of  claim 11 , wherein the image sharpness criterion indicates an image in the stack of images having a highest number of pixels in focus among the images included in the stack of images. 
     
     
         14 . The method of  claim 13 , wherein the image in the stack of images having the highest number of pixels in focus is an all-in focus image. 
     
     
         15 . A device comprising
 at least one processor configured to   encode a stack of images of a same scene focused at a different focalization distances from one image to another, wherein the at least one processor being configured to encode the stack of images comprises the at least one processor being further configured to:   encode information representing an image of the stack of images, the image being selected in the stack of images according to an image sharpness criterion, and reconstruct the image into a reconstructed image;   encode at least one other image of the stack of images by prediction from at least the reconstructed image.   
     
     
         16 . The device of  claim 15 , wherein the image sharpness criterion corresponds to a number of pixels in focus in an image. 
     
     
         17 . The method of  claim 15 , wherein the image sharpness criterion indicates an image in the stack of images having a highest number of pixels in focus among the images included in the stack of images. 
     
     
         18 . The method of  claim 17 , wherein the image in the stack of images having the highest number of pixels in focus is an all-in focus image. 
     
     
         19 . A device comprising
 at least one processor configured to   decode a stack of images comprising a set of images focused at a different focalization distances from one image to another, wherein the at least one processor being configured to decode the stack of images comprises the at least one processor being configured to:
 decode information representing an image of the stack of images, the image of the stack of images fulfilling an image sharpness criterion, 
 reconstruct at least one other image of the stack of images by prediction from at least the decoded image. 
   
     
     
         20 . The device of  claim 19 , wherein the image sharpness criterion corresponds to a number of pixels in focus in an image. 
     
     
         21 . The method of  claim 19 , wherein the image sharpness criterion indicates an image in the stack of images having a highest number of pixels in focus among the images included in the stack of images. 
     
     
         22 . The method of  claim 21 , wherein the image in the stack of images having the highest number of pixels in focus is an all-in focus image. 
     
     
         23 . A non-transitory computer-readable medium having program code instructions recorded thereon and capable of being executed by a processor for implementing a method according to  claim 1 .