Image processing circuit

摘要

An image processing circuit which adds, by means of a yellow color image data, forgery tracing information to yellow, magenta and cyan color image data obtained by reading out of an original. A tracing information adder replaces the read-out yellow color image data with a yellow color image of a higher density in a low-density area where the density of the read-out yellow color image data is equal to or below a set threshold value. In a high-density area where the density of the read-out yellow color image data exceeds the set threshold value, the tracing information is added by adding a predetermined value to the read-out yellow color image data.