c1 := YCbCr{uint8(i), 0x40, 0xc0}
		if err := eq(c0, c1); err != nil {
			t.Errorf("i=0x%02x:\n%v", i, err)
		}
	}
}

// TestCMYKRoundtrip tests that a subset of RGB space can be converted to CMYK
// and back to within 1/256 tolerance.
func TestCMYKRoundtrip(t *testing.T) {
	for r := 0; r < 256; r += 7 {
		for g := 0; g < 256; g += 5 {
			for b := 0; b < 256; b += 3 {