int gdImageCompare (gdImagePtr im1, gdImagePtr im2)
{
	int x, y;
	int p1, p2;
	int cmpStatus = 0;
	int sx, sy;

	if (im1->interlace != im2->interlace) {
		cmpStatus |= GD_CMP_INTERLACE;
	}

	if (im1->transparent != im2->transparent) {
		cmpStatus |= GD_CMP_TRANSPARENT;
	}

	if (im1->trueColor != im2->trueColor) {
		cmpStatus |= GD_CMP_TRUECOLOR;
	}

	sx = im1->sx;
	if (im1->sx != im2->sx) {
		cmpStatus |= GD_CMP_SIZE_X + GD_CMP_IMAGE;
		if (im2->sx < im1->sx) {
			sx = im2->sx;
		}
	}

	sy = im1->sy;
	if (im1->sy != im2->sy) {
		cmpStatus |= GD_CMP_SIZE_Y + GD_CMP_IMAGE;
		if (im2->sy < im1->sy) {
			sy = im2->sy;
		}
	}

	if (im1->colorsTotal != im2->colorsTotal) {
		cmpStatus |= GD_CMP_NUM_COLORS;
	}

	for (y = 0; y < sy; y++) {
		for (x = 0; x < sx; x++) {
			p1 = im1->trueColor ? gdImageTrueColorPixel(im1, x, y) : gdImagePalettePixel(im1, x, y);
			p2 = im2->trueColor ? gdImageTrueColorPixel(im2, x, y) : gdImagePalettePixel(im2, x, y);

			if (gdImageRed(im1, p1) != gdImageRed(im2, p2)) {
				cmpStatus |= GD_CMP_COLOR + GD_CMP_IMAGE;
				break;
			}
			if (gdImageGreen(im1, p1) != gdImageGreen(im2, p2)) {
				cmpStatus |= GD_CMP_COLOR + GD_CMP_IMAGE;
				break;
			}
			if (gdImageBlue(im1, p1) != gdImageBlue(im2, p2)) {
				cmpStatus |= GD_CMP_COLOR + GD_CMP_IMAGE;
				break;
			}
#if 0
			/* Soon we'll add alpha channel to palettes */
			if (gdImageAlpha(im1, p1) != gdImageAlpha(im2, p2)) {
				cmpStatus |= GD_CMP_COLOR + GD_CMP_IMAGE;
				break;
			}
#endif
		}
		if (cmpStatus & GD_CMP_COLOR) {
			break;
		}
	}

	return cmpStatus;
}