A program product comprising a computer-usable medium having computer-readable program code embodied thereon for causing a computer to perform an image processing method, the method comprising:
- reading an image of a document by using a first image sensor unit including multiple image sensor chips arranged in a line to convert light incident from the document into electrical signals;
- calculating chroma data from an image signal constituted by the electrical signals of the image read at the reading;
- adjusting the chroma by using the chroma data calculated at the calculating;
- and
- performing, only on a low-chroma image signal, a conversion process for reducing the chroma based on the adjusting to suppress color irregularities occurring at intervals corresponding to widths of the multiple image sensor chips of the first image sensor unit.