Patent ID: 7259891

Claim:
A method of image compression comprising: a first region separation step of separating into regions containing black pixels and regions not containing black pixels in units of K rows (where K is an integer of one or more) by scanning an image in a main scanning direction; a second region separating step of separating regions containing black pixels and regions not containing black pixels in single column units by scanning in an auxiliary scanning direction intersecting said main scanning direction in logical rows defined by L (where L is an integer of one or more) rows including at least one row containing black pixels obtained by the first region separating step; a third region separating step of separating regions in which black pixels increase or decrease continuously in the same direction of the auxiliary scanning direction in the logical row in accordance with the separation results of said second region separating step; and an encoding step of encoding by using the regions obtained in said first, second and third region separating step as elements; wherein the encoding step includes a step of encoding the regions separated by said third region separating step with the number of columns of said region, the pixel value of the leading column of the region and the amount of change of the black pixels of each column of the second and subsequent columns of said region with respect to the immediately preceding column.