An image, in which a character image and a photographic image are mixed, is efficiently encoded while preventing image quality deterioration. Hence, image data including foreground pixels and background pixels is input. In the image data, first image data is generated by setting a pixel value that does not occur as the foreground pixel to the pixel value of the background pixel based on the histogram of pixel values that occur as foreground pixels, and the first image data is encoded. In the image data, second image data is generated by setting a value based on the pixel value of the background pixel to the pixel value of the foreground pixel, and the second image data is encoded.