github.com/zach-klippenstein/go@v0.0.0-20150108044943-fcfbeb3adf58/src/image/color/ycbcr_test.go (about)

     1  // Copyright 2011 The Go Authors. All rights reserved.
     2  // Use of this source code is governed by a BSD-style
     3  // license that can be found in the LICENSE file.
     4  
     5  package color
     6  
     7  import (
     8  	"testing"
     9  )
    10  
    11  func delta(x, y uint8) uint8 {
    12  	if x >= y {
    13  		return x - y
    14  	}
    15  	return y - x
    16  }
    17  
    18  // Test that a subset of RGB space can be converted to YCbCr and back to within
    19  // 1/256 tolerance.
    20  func TestRoundtrip(t *testing.T) {
    21  	for r := 0; r < 255; r += 7 {
    22  		for g := 0; g < 255; g += 5 {
    23  			for b := 0; b < 255; b += 3 {
    24  				r0, g0, b0 := uint8(r), uint8(g), uint8(b)
    25  				y, cb, cr := RGBToYCbCr(r0, g0, b0)
    26  				r1, g1, b1 := YCbCrToRGB(y, cb, cr)
    27  				if delta(r0, r1) > 1 || delta(g0, g1) > 1 || delta(b0, b1) > 1 {
    28  					t.Fatalf("r0, g0, b0 = %d, %d, %d   r1, g1, b1 = %d, %d, %d", r0, g0, b0, r1, g1, b1)
    29  				}
    30  			}
    31  		}
    32  	}
    33  }