An image processing apparatus for generating a luminance signal from a digital image signal comprising pixels in accordance with an RGB Bayer arrangement, the image processing apparatus comprising: generation means for receiving the digital image signal, generating a first image signal using the received digital image signal, the first image signal comprising an R color plane, a G color plane and a B color plane generated by the generation means so that each pixel has the G, R, and B signals, reduction means performing a low-pass filtering process and a downsampling process on the first image signal to generate a second image signal, the first image signal including therefore a frequency band higher than a frequency band of the second image signal; noise suppression means (206, 209) for performing a noise suppression process on each pixel of the first image signal and the second image signal; enlargement means for performing an upsampling process on the second image signal on which the noise suppression process has been performed; synthesis means for synthesizing, using the first image signal on which the noise suppression process has been performed and the second image signal on which the upsampling process has been performed, an image signal based on an edge component of each pixel of the first image signal, outputting corresponding R, G and B color planes; first luminance signal generation means for performing a compensation process on an image signal comprising signals of pixels of the RGB Bayer arrangement, in order to make each of the pixels have signals of all the colors, and generating a first luminance signal of each pixel using the image signal on which the compensation process has been performed; second luminance signal generation means for taking a value of each pixel of the image signal comprising signals of pixels of the RGB Bayer arrangement on which the compensation process has not been performed as a second luminance signal of each pixel, the second luminance signal having a higher resolution than that of the first luminance signal; and luminance signal mixing means for outputting a luminance signal based on the first and second luminance signals or a luminance signal obtained by selecting one of the first and second luminance signals; characterized in that the image processing apparatus further comprises rearrangement means for rearranging the image signal synthesized by the synthesis means to generate the image signal comprising signals of pixels of the RGB Bayer arrangement, the first luminance signal generation means performs the compensation process on the image signal generated by the rearrangement means, and the second luminance signal generation means takes the value of each pixel of the image signal generated by the rearrangement means as the second luminance signal of each pixel. generation means for receiving the digital image signal, generating a first image signal using the received digital image signal, the first image signal comprising an R color plane, a G color plane and a B color plane generated by the generation means so that each pixel has the G, R, and B signals, reduction means performing a low-pass filtering process and a downsampling process on the first image signal to generate a second image signal, the first image signal including therefore a frequency band higher than a frequency band of the second image signal; noise suppression means (206, 209) for performing a noise suppression process on each pixel of the first image signal and the second image signal; enlargement means for performing an upsampling process on the second image signal on which the noise suppression process has been performed; synthesis means for synthesizing, using the first image signal on which the noise suppression process has been performed and the second image signal on which the upsampling process has been performed, an image signal based on an edge component of each pixel of the first image signal, outputting corresponding R, G and B color planes; first luminance signal generation means for performing a compensation process on an image signal comprising signals of pixels of the RGB Bayer arrangement, in order to make each of the pixels have signals of all the colors, and generating a first luminance signal of each pixel using the image signal on which the compensation process has been performed; second luminance signal generation means for taking a value of each pixel of the image signal comprising signals of pixels of the RGB Bayer arrangement on which the compensation process has not been performed as a second luminance signal of each pixel, the second luminance signal having a higher resolution than that of the first luminance signal; and luminance signal mixing means for outputting a luminance signal based on the first and second luminance signals or a luminance signal obtained by selecting one of the first and second luminance signals; characterized in that the image processing apparatus further comprises rearrangement means for rearranging the image signal synthesized by the synthesis means to generate the image signal comprising signals of pixels of the RGB Bayer arrangement, the first luminance signal generation means performs the compensation process on the image signal generated by the rearrangement means, and the second luminance signal generation means takes the value of each pixel of the image signal generated by the rearrangement means as the second luminance signal of each pixel.