Image coding method and apparatus using spatial predictive coding of chrominance and image decoding method and apparatus

Abstract

A coding method including dividing pixels of a chrominance component of an input image into blocks having a predetermined size; selecting one among a direct current prediction method, a vertical prediction method, a horizontal prediction method, and a hybrid prediction method according to a user's input; generating a prediction value of each pixel in a current block to be predictively coded, using at least one pixel value among pixel values in an upper reference block adjacent to the current block and in a side reference block adjacent to the current block, according to the selected prediction method; generating a differential value between the prediction value and a corresponding real pixel value in the current block; and coding the differential value and information on the selected prediction method using a predetermined coding method.

1 . A coding method comprising:
 (a) dividing pixels of a chrominance component of an input image into blocks having a predetermined size;   (b) selecting one among a direct current prediction method, a vertical prediction method, a horizontal prediction method, and a hybrid prediction method according to a user's input;   (c) generating a prediction value of each pixel in a current block to be predictively coded, using at least one pixel value among pixel values in an upper reference block adjacent to the current block and in a side reference block adjacent to the current block, according to the selected prediction method;   (d) generating a differential value between the prediction value and a corresponding real pixel value in the current block; and   (e) coding the differential value and information on the selected prediction method using a predetermined coding method.   
     
     
         2 . The coding method of  claim 1 , wherein the hybrid prediction method comprises calculating a vertical variation and a horizontal variation with respect to the current block using pixel values adjacent to the current block in the upper and side reference blocks, dividing the current block into a predetermined number of regions according to the vertical and horizontal variations, and generating prediction values of respective pixels in each region using the pixel values in the upper and side reference blocks. 
     
     
         3 . The coding method of  claim 2 , wherein the hybrid prediction method comprises comparing the vertical variation with the horizontal variation, dividing the current block into an upper region and a lower region in a vertical direction when the horizontal variation is greater than the vertical variation, generating prediction values in the upper region using pixel values in the upper reference block, and generating prediction values in the lower region using pixel values in the side reference block. 
     
     
         4 . The coding method of  claim 2 , wherein the hybrid prediction method comprises comparing the vertical variation with the horizontal variation, dividing the current block into a first region and a second region in a horizontal direction when the vertical variation is greater than the horizontal variation, generating prediction values in the first region adjacent to the side reference block using pixel values in the side reference block, and generating prediction values in the second region using pixel values in the upper reference block. 
     
     
         5 . A non-transitory computer readable recording medium storing a program code for executing the coding method of  claim 1  in a computer. 
     
     
         6 . A coding apparatus comprising:
 a selector, which selects one among predetermined prediction methods comprising a direct current prediction method, a vertical prediction method, a horizontal prediction method, and a hybrid prediction method according to a user's input;   a predictor, which generates a prediction value of each pixel in a current block to be predictively coded among blocks having a predetermined size, into which a chrominance component of an input image is divided, using at least one pixel value among pixel values in an upper reference block above the current block and in a side reference block on left of the current block, according to the selected prediction method;   a differential value generator, which generates a differential value between the prediction value and a corresponding real pixel value in the current block; and   a coder, which codes the differential value and information on the selected prediction method using a predetermined coding method.   
     
     
         7 . The coding apparatus of  claim 6 , wherein the predictor comprises a hybrid predictor, and the hybrid predictor calculates a vertical variation and a horizontal variation with respect to the current block using pixel values adjacent to the current block in the upper and side reference blocks, divides the current block into a predetermined number of regions according to the vertical and horizontal variations, and generates prediction values of respective pixels in each region using the pixel values in the upper and side reference blocks. 
     
     
         8 . The coding apparatus of  claim 7 , wherein the hybrid predictor compares the vertical variation with the horizontal variation, divides the current block into an upper region and a lower region in a vertical direction when the horizontal variation is greater than the vertical variation, generates prediction values in the upper region using pixel values in the upper reference block, and generates prediction values in the lower region using pixel values in the side reference block. 
     
     
         9 . The coding apparatus of  claim 7 , wherein the hybrid predictor compares the vertical variation with the horizontal variation, divides the current block into a first region and a second region in a horizontal, direction when the vertical variation is greater than the horizontal variation, generates prediction values in the first region adjacent to the side reference block using pixel values in the side reference block, and generates prediction values in the second region using pixel values in the upper reference block.