1 files changed, 33 insertions, 0 deletions
diff --git a/src/image/color/ycbcr_test.go b/src/image/color/ycbcr_test.go
new file mode 100644
index 000000000..92a0e6ff1
--- /dev/null
+++ b/src/image/color/ycbcr_test.go
@@ -0,0 +1,33 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package color
+
+import (
+	"testing"
+)
+
+func delta(x, y uint8) uint8 {
+	if x >= y {
+		return x - y
+	}
+	return y - x
+}
+
+// Test that a subset of RGB space can be converted to YCbCr and back to within
+// 1/256 tolerance.
+func TestRoundtrip(t *testing.T) {
+	for r := 0; r < 255; r += 7 {
+		for g := 0; g < 255; g += 5 {
+			for b := 0; b < 255; b += 3 {
+				r0, g0, b0 := uint8(r), uint8(g), uint8(b)
+				y, cb, cr := RGBToYCbCr(r0, g0, b0)
+				r1, g1, b1 := YCbCrToRGB(y, cb, cr)
+				if delta(r0, r1) > 1 || delta(g0, g1) > 1 || delta(b0, b1) > 1 {
+					t.Fatalf("r0, g0, b0 = %d, %d, %d   r1, g1, b1 = %d, %d, %d", r0, g0, b0, r1, g1, b1)
+				}
+			}
+		}
+	}
+}