In bitmapping an input rendering command to a bitmap, a logic operation designated by the rendering command is analyzed in accordance with the source and pattern as the logic operation target and a logic operation code. On the basis of the analysis result, an additional information operation corresponding to each pixel of the bitmap is created. On the basis of the additional information operation, additional information of each pixel is created. When image processing based on the additional information is executed for the bitmap, high-quality output image data can be created.