1. An image processing device configured to process image data configured of a plurality of pixels which are imaged by a color image sensor to measure one color from a plurality of color information for configuring compounded color information, said image processing device comprising: gray level transforming processing means configured to receive input of said image data, perform gray level transforming, and output image data having all said plurality of color information by each pixel being configured by one of said plurality of color information for configuring compounded color information; said gray level transforming processing means further including first gray value computing means configured to compute a first gray value according to the brightness of a pixel of interest which exists in a pixel location of interest; second gray value computing means configured to compute a second gray value by performing gray value transforming as to said first gray value which is computed with said first gray value computing means; and pixel value gray level transforming means configured to compute a pixel value subjected to gray level transforming of said pixel of interest, based on said first gray value computed by said first gray value computing means, said second gray value computed by said second gray value computing means, and the pixel value of said pixel of interest.