Image forming apparatus for forming a plurality of screened images

1. Field of the Invention An image forming apparatus includes an image reader for reading images, a memory for storing images read by the image reader, a compression circuit for compressing an arbitrary portion of an image placed on a page memory, a compressed image memory for storing images compressed by the compression circuit, a decompression circuit for decompressing images placed on the compressed image memory, a page memory for developing images decompressed by the decompression circuit, and a printer for outputting images on the page memory. When a plurality of images stored in the memory are to be screened, combined on the page memory and to be output, the images are developed such that screen patterns of respective images to be combined are superposed on the page memory. As a result, an image forming apparatus which is capable of screening, combining and printing a plurality of stored images without increasing memory capacity is provided.