PURPOSE: To process a logical pixel image having high horizontal resolution by performing raster scanning so as to restore a pixel image of predetermined resolution by elongating the respective pixels of an altered pixel image in an axial direction.

CONSTITUTION: LENGTH is set to zero in a block 102 and POINTER is initialized to a first dot of each logical pixel image in a block 104 and WIDTH is initialized to the number of pixels in each image pixel line and LAST is cleared in a block 106. Four continuous pixels are obtained from logical pixel image (line) arrangement in a block 108. Control is transmitted to the start of a THIN-RIGHT processor in a block 110 and, after the return from the THIN-RIGHT processor in a block 112, LAST is written in the pixel image altered within a CURRENT pixel position in a block 114.