To provide a method for extracting colors of an image from the one with uneven luminance due to illumination and an image processor using the method with comparatively simple structure and high-speed operation processing.

This image processor is constituted to calculate one or plural difference values among the difference values between an R value and a G value, the difference value between a B value and the G value, the difference value between the R value and the B value in addition to the R value, the G value and the B value of respective pixels in an image pickup area 11a, to set threshold values for the R value, the G value, the B value and the one or plural difference values among the difference values between the R value and the G value, the difference value between the B value and the G value, the difference value between the R value and the B value in one or plural selected pixels and to extract the pixel in which the R value, the G value, the B value and one or plural difference values among the difference value between the R value and the G value, the difference value between the B value and the G value, the difference value between the R value and the B value of an optional pixel in the image-pickup area 11a does not the threshold as the pixel with the same color as that of the selected pixel.