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Source file src/image/color/ycbcr_test.go

Documentation: image/color

  // 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 (
  	"fmt"
  	"testing"
  )
  
  func delta(x, y uint8) uint8 {
  	if x >= y {
  		return x - y
  	}
  	return y - x
  }
  
  func eq(c0, c1 Color) error {
  	r0, g0, b0, a0 := c0.RGBA()
  	r1, g1, b1, a1 := c1.RGBA()
  	if r0 != r1 || g0 != g1 || b0 != b1 || a0 != a1 {
  		return fmt.Errorf("got  0x%04x 0x%04x 0x%04x 0x%04x\nwant 0x%04x 0x%04x 0x%04x 0x%04x",
  			r0, g0, b0, a0, r1, g1, b1, a1)
  	}
  	return nil
  }
  
  // TestYCbCrRoundtrip tests that a subset of RGB space can be converted to YCbCr
  // and back to within 2/256 tolerance.
  func TestYCbCrRoundtrip(t *testing.T) {
  	for r := 0; r < 256; r += 7 {
  		for g := 0; g < 256; g += 5 {
  			for b := 0; b < 256; 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) > 2 || delta(g0, g1) > 2 || delta(b0, b1) > 2 {
  					t.Fatalf("\nr0, g0, b0 = %d, %d, %d\ny,  cb, cr = %d, %d, %d\nr1, g1, b1 = %d, %d, %d",
  						r0, g0, b0, y, cb, cr, r1, g1, b1)
  				}
  			}
  		}
  	}
  }
  
  // TestYCbCrToRGBConsistency tests that calling the RGBA method (16 bit color)
  // then truncating to 8 bits is equivalent to calling the YCbCrToRGB function (8
  // bit color).
  func TestYCbCrToRGBConsistency(t *testing.T) {
  	for y := 0; y < 256; y += 7 {
  		for cb := 0; cb < 256; cb += 5 {
  			for cr := 0; cr < 256; cr += 3 {
  				x := YCbCr{uint8(y), uint8(cb), uint8(cr)}
  				r0, g0, b0, _ := x.RGBA()
  				r1, g1, b1 := uint8(r0>>8), uint8(g0>>8), uint8(b0>>8)
  				r2, g2, b2 := YCbCrToRGB(x.Y, x.Cb, x.Cr)
  				if r1 != r2 || g1 != g2 || b1 != b2 {
  					t.Fatalf("y, cb, cr = %d, %d, %d\nr1, g1, b1 = %d, %d, %d\nr2, g2, b2 = %d, %d, %d",
  						y, cb, cr, r1, g1, b1, r2, g2, b2)
  				}
  			}
  		}
  	}
  }
  
  // TestYCbCrGray tests that YCbCr colors are a superset of Gray colors.
  func TestYCbCrGray(t *testing.T) {
  	for i := 0; i < 256; i++ {
  		c0 := YCbCr{uint8(i), 0x80, 0x80}
  		c1 := Gray{uint8(i)}
  		if err := eq(c0, c1); err != nil {
  			t.Errorf("i=0x%02x:\n%v", i, err)
  		}
  	}
  }
  
  // TestNYCbCrAAlpha tests that NYCbCrA colors are a superset of Alpha colors.
  func TestNYCbCrAAlpha(t *testing.T) {
  	for i := 0; i < 256; i++ {
  		c0 := NYCbCrA{YCbCr{0xff, 0x80, 0x80}, uint8(i)}
  		c1 := Alpha{uint8(i)}
  		if err := eq(c0, c1); err != nil {
  			t.Errorf("i=0x%02x:\n%v", i, err)
  		}
  	}
  }
  
  // TestNYCbCrAYCbCr tests that NYCbCrA colors are a superset of YCbCr colors.
  func TestNYCbCrAYCbCr(t *testing.T) {
  	for i := 0; i < 256; i++ {
  		c0 := NYCbCrA{YCbCr{uint8(i), 0x40, 0xc0}, 0xff}
  		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 {
  				r0, g0, b0 := uint8(r), uint8(g), uint8(b)
  				c, m, y, k := RGBToCMYK(r0, g0, b0)
  				r1, g1, b1 := CMYKToRGB(c, m, y, k)
  				if delta(r0, r1) > 1 || delta(g0, g1) > 1 || delta(b0, b1) > 1 {
  					t.Fatalf("\nr0, g0, b0 = %d, %d, %d\nc, m, y, k = %d, %d, %d, %d\nr1, g1, b1 = %d, %d, %d",
  						r0, g0, b0, c, m, y, k, r1, g1, b1)
  				}
  			}
  		}
  	}
  }
  
  // TestCMYKToRGBConsistency tests that calling the RGBA method (16 bit color)
  // then truncating to 8 bits is equivalent to calling the CMYKToRGB function (8
  // bit color).
  func TestCMYKToRGBConsistency(t *testing.T) {
  	for c := 0; c < 256; c += 7 {
  		for m := 0; m < 256; m += 5 {
  			for y := 0; y < 256; y += 3 {
  				for k := 0; k < 256; k += 11 {
  					x := CMYK{uint8(c), uint8(m), uint8(y), uint8(k)}
  					r0, g0, b0, _ := x.RGBA()
  					r1, g1, b1 := uint8(r0>>8), uint8(g0>>8), uint8(b0>>8)
  					r2, g2, b2 := CMYKToRGB(x.C, x.M, x.Y, x.K)
  					if r1 != r2 || g1 != g2 || b1 != b2 {
  						t.Fatalf("c, m, y, k = %d, %d, %d, %d\nr1, g1, b1 = %d, %d, %d\nr2, g2, b2 = %d, %d, %d",
  							c, m, y, k, r1, g1, b1, r2, g2, b2)
  					}
  				}
  			}
  		}
  	}
  }
  
  // TestCMYKGray tests that CMYK colors are a superset of Gray colors.
  func TestCMYKGray(t *testing.T) {
  	for i := 0; i < 256; i++ {
  		if err := eq(CMYK{0x00, 0x00, 0x00, uint8(255 - i)}, Gray{uint8(i)}); err != nil {
  			t.Errorf("i=0x%02x:\n%v", i, err)
  		}
  	}
  }
  
  func TestPalette(t *testing.T) {
  	p := Palette{
  		RGBA{0xff, 0xff, 0xff, 0xff},
  		RGBA{0x80, 0x00, 0x00, 0xff},
  		RGBA{0x7f, 0x00, 0x00, 0x7f},
  		RGBA{0x00, 0x00, 0x00, 0x7f},
  		RGBA{0x00, 0x00, 0x00, 0x00},
  		RGBA{0x40, 0x40, 0x40, 0x40},
  	}
  	// Check that, for a Palette with no repeated colors, the closest color to
  	// each element is itself.
  	for i, c := range p {
  		j := p.Index(c)
  		if i != j {
  			t.Errorf("Index(%v): got %d (color = %v), want %d", c, j, p[j], i)
  		}
  	}
  	// Check that finding the closest color considers alpha, not just red,
  	// green and blue.
  	got := p.Convert(RGBA{0x80, 0x00, 0x00, 0x80})
  	want := RGBA{0x7f, 0x00, 0x00, 0x7f}
  	if got != want {
  		t.Errorf("got %v, want %v", got, want)
  	}
  }
  
  var sink8 uint8
  var sink32 uint32
  
  func BenchmarkYCbCrToRGB(b *testing.B) {
  	// YCbCrToRGB does saturating arithmetic.
  	// Low, middle, and high values can take
  	// different paths through the generated code.
  	b.Run("0", func(b *testing.B) {
  		for i := 0; i < b.N; i++ {
  			sink8, sink8, sink8 = YCbCrToRGB(0, 0, 0)
  		}
  	})
  	b.Run("128", func(b *testing.B) {
  		for i := 0; i < b.N; i++ {
  			sink8, sink8, sink8 = YCbCrToRGB(128, 128, 128)
  		}
  	})
  	b.Run("255", func(b *testing.B) {
  		for i := 0; i < b.N; i++ {
  			sink8, sink8, sink8 = YCbCrToRGB(255, 255, 255)
  		}
  	})
  }
  
  func BenchmarkRGBToYCbCr(b *testing.B) {
  	// RGBToYCbCr does saturating arithmetic.
  	// Different values can take different paths
  	// through the generated code.
  	b.Run("0", func(b *testing.B) {
  		for i := 0; i < b.N; i++ {
  			sink8, sink8, sink8 = RGBToYCbCr(0, 0, 0)
  		}
  	})
  	b.Run("Cb", func(b *testing.B) {
  		for i := 0; i < b.N; i++ {
  			sink8, sink8, sink8 = RGBToYCbCr(0, 0, 255)
  		}
  	})
  	b.Run("Cr", func(b *testing.B) {
  		for i := 0; i < b.N; i++ {
  			sink8, sink8, sink8 = RGBToYCbCr(255, 0, 0)
  		}
  	})
  }
  
  func BenchmarkYCbCrToRGBA(b *testing.B) {
  	// RGB does saturating arithmetic.
  	// Low, middle, and high values can take
  	// different paths through the generated code.
  	b.Run("0", func(b *testing.B) {
  		c := YCbCr{0, 0, 0}
  		for i := 0; i < b.N; i++ {
  			sink32, sink32, sink32, sink32 = c.RGBA()
  		}
  	})
  	b.Run("128", func(b *testing.B) {
  		c := YCbCr{128, 128, 128}
  		for i := 0; i < b.N; i++ {
  			sink32, sink32, sink32, sink32 = c.RGBA()
  		}
  	})
  	b.Run("255", func(b *testing.B) {
  		c := YCbCr{255, 255, 255}
  		for i := 0; i < b.N; i++ {
  			sink32, sink32, sink32, sink32 = c.RGBA()
  		}
  	})
  }
  
  func BenchmarkNYCbCrAToRGBA(b *testing.B) {
  	// RGBA does saturating arithmetic.
  	// Low, middle, and high values can take
  	// different paths through the generated code.
  	b.Run("0", func(b *testing.B) {
  		c := NYCbCrA{YCbCr{0, 0, 0}, 0xff}
  		for i := 0; i < b.N; i++ {
  			sink32, sink32, sink32, sink32 = c.RGBA()
  		}
  	})
  	b.Run("128", func(b *testing.B) {
  		c := NYCbCrA{YCbCr{128, 128, 128}, 0xff}
  		for i := 0; i < b.N; i++ {
  			sink32, sink32, sink32, sink32 = c.RGBA()
  		}
  	})
  	b.Run("255", func(b *testing.B) {
  		c := NYCbCrA{YCbCr{255, 255, 255}, 0xff}
  		for i := 0; i < b.N; i++ {
  			sink32, sink32, sink32, sink32 = c.RGBA()
  		}
  	})
  }
  

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