Patent ID: 7154420

Claim:
In an image coding apparatus for an image in which color code data of 2 bits corresponds to each pixel on an image, the image coding apparatus comprising: color code difference detecting means for detecting difference data between color code data of opposing pixel positions in divided horizontal lines and adjacent immediately-preceding divided lines with respect to each divided horizontal line within blocks forming an image, each time the blocks of the image equally divided into M (M: an arbitrary integer greater than 1) blocks in the horizontal direction are updated; and run-length coding means for run-length coding a coded word corresponding to a first run in a state in which said run contains difference information, except when said run is a special run, and coded words corresponding to runs other than said first run in a state in which said run contains transition type information indicating a type of transition of the difference data of an immediately-preceding run to the difference data of said run instead of difference information of said run, except when said run is a special run, each time difference data corresponding to a divided horizontal line from said color code difference detecting means is run-length coded at every run.