The compression processing unit 30 of the image processing apparatus makes the color conversion process section 50 to the layout analysis processing section 53 extract the text string region, and makes the foreground layer generating section 54 extract the foreground pixel from the text string region to generate the foreground layer. The line detection process section 52 extracts the line art from the input image data, and removes the pixel block configuring the line art from the foreground pixel-block mask generated by the foreground extracting section 51. The layout analysis processing section 53 estimates the direction of the text string in accordance with the distance of the foreground regions and the number of connected foreground regions, and merges the foreground regions connected in the estimated direction, to extract the text string region.