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// 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)

                                }

                        }

                }

        }

}