An image processing system for processing an image represented by run-lengths includes a first block for, when a run-length is less than a base number which is a n-th power of "2" where n is an integer, representing the run-length by one byte, and a second block for, when a run-length is equal to or greater than the base number, representing the run-length by a first part corresponding to a multiple of the base number and a second part corresponding to a value less than the base number, each of the first part and the second part being represented by one byte, wherein run-length data obtained by the first block or the second block is processed.