write_image (save, "build/test/image_test_" + suffix + ".png", "RGB");
check_image ("build/test/image_test_" + suffix + ".png", private_data / ("image_test_" + suffix + ".png"));
write_image (save, "build/test/image_test_" + suffix + ".png", "RGB");
check_image ("build/test/image_test_" + suffix + ".png", private_data / ("image_test_" + suffix + ".png"));