In a color image processing apparatus, in a compression process section (an image compressing apparatus), when an original document is compressed, the edges of black texts and/or line drawings in the original document is detected, then a foreground layer (a first image) is generated in which the detected edges are expressed in the form of a binary image, and then lossless compression is performed on the foreground layer. Further, a background layer (a second image) is generated in which a density difference of the edges from the other parts in the original document is reduced, and then lossy compression is performed on the background layer. Then, these layers are combined into a compressed file.