1. An image processing apparatus comprising: a gradient calculating part configured to calculate intensity gradient at each pixel in a color image produced by an image capturing system; a first color blur determining part configured to determine that a pixel at which the intensity gradient satisfies a color blur condition using a first threshold is a possible color blur pixel; and a second color blur determining part configured to detect a saturated pixel in the color image, and to determine, when a distance between the saturated pixel and the possible color blur pixel is within a second threshold, that the possible color blur pixel is a color blur pixel, wherein the first and second color blur determining parts are respectively configured to change the first and second thresholds depending on at least one of luminance and chroma of the possible color blur pixel.