An image reading apparatus is composed of an image input unit for obtaining multi-valued image data by reading an image optically; an image processing unit for performing image processing including screen processing on the multi-valued image data obtained by the image input unit; a data converting unit for converting image data obtained by the image processing of the image processing unit into a form that is described in a page description language; and an image output unit for outputting image data obtained by the conversion of the data converting unit to the outside.