Patent ID: 8471864

Claim:
An image processor comprising: a first dither data memory storing a first dither matrix; a second dither data memory storing a second dither matrix, the second dither matrix being configured of a plurality of sub-dither matrices, each sub-dither matrix having a plurality of elements each assigned with a threshold value falling in a range from a maximum threshold value to a minimum threshold value, each threshold value smaller than or equal to a predetermined intermediate threshold value being assigned in at least two corresponding sub-dither matrices of the plurality of sub-matrices, each threshold value greater than the predetermined intermediate threshold value being assigned in only one corresponding sub-dither matrix of the plurality of sub-dither matrices; a selecting unit selecting one of the first dither matrix and the second dither matrix; and a converting unit converting multi-value image data to binary data by comparing density of the multi-value image data to the threshold value set in corresponding element of the one of the first dither matrix and the second dither matrix selected by the selecting unit.