The generation of a false color is prevented. In a pixel mixture block, pixels of the same color are mixed. For example, red pixels are mixed to obtain a red mixed pixel and blue pixels are mixed to obtain a blue mixed pixel. Green pixels in an odd-numbered row and pixels in an even-numbered row are separately mixed to obtain a green mixed pixel and a green mixed pixel. A correlation direction in a partial color image 1 is detected from these mixed pixels. Interpolation pixels are generated from the mixed pixels according to the correlation direction such that a false color is not generated.