PURPOSE: To make it possible to simply and easily perform an image conversion processing and to faithfully reproduce the processing by reading the image of a screen as image data by dots, performing a conversion processing for the data as raster line data and recording the obtained raster line data in the memory and recording medium of a computer.

CONSTITUTION: As for the image read as dots in a computer 3 by an image scanner 2, the scanning direction of the image scanner 2 is investigated by defining a preliminarily set origin as an origin by using a conversion program 4. The dot value in the part where the image of an original picture on the scanning line is not formed is defined as 0 and the dot value composing the image is defined as 1. A linear storage is performed between the dot on the contour of the origin of the image existing on the scanning line and the dot on the side of an end point and the parts within the contour of the image is converted as the respective raster line data. The data is stored in the memory of a computer 3, is coded and is recorded in a recording medium 5.