According to the present invention, an image signal processor, comprising a receiver, a mixing block, and an adjustment block, is provided. The receiver receives first, second, and third color pixel signals which an imaging device outputs. The mixing block generates first, second, and third color mixed pixel signals. The first, second, and third color mixed pixel signals are generated by mixing the first, second, and third color pixel signals generated by all the first, second, and third color pixels occupying a space of which the area is a second predetermined area whose the center is in agreement with the center of the first, second, and third color mixed pixel areas, respectively. The adjustment block adjusts the signal levels of the first, second, and third color mixed pixel signals based on first, second, and third pixel numbers.