Patent ID: 8553985

Claim:
An image processing apparatus which performs boundary line extraction for raster image data, comprising: a detection unit configured to detect a color region formed from a plurality of pixels connected in an oblique direction of an 8-neighbor connection in the image data; a determination unit configured to determine whether the oblique 8-neighbor connection in the color region detected by said detection unit is to be modified to a 4-neighbor connection, in accordance with a connection state of the pixels connected by the oblique 8-neighbor connection and pixels surrounding the pixels connected by the oblique 8-neighbor connection; a modification unit configured to modify the oblique 8-neighbor connection in the color region, a modification of which is determined by said determination unit, by converting a pixel value of a pixel neighboring the pixels connected by the oblique 8-neighbor connection; and an extraction unit configured to extract a boundary line from image data modified by said modification unit.