1. package chroma

  2. 

  3. import (

  4. 	"math"

  5. 	"testing"

  6. 

  7. 	assert "github.com/alecthomas/assert/v2"

  8. )

  9. 

  10. func TestColourRGB(t *testing.T) {

  11. 	colour := ParseColour("#8913af")

  12. 	assert.Equal(t, uint8(0x89), colour.Red())

  13. 	assert.Equal(t, uint8(0x13), colour.Green())

  14. 	assert.Equal(t, uint8(0xaf), colour.Blue())

  15. }

  16. 

  17. func TestColourString(t *testing.T) {

  18. 	assert.Equal(t, "#8913af", ParseColour("#8913af").String())

  19. }

  20. 

  21. func distance(a, b uint8) uint8 {

  22. 	if a < b {

  23. 		return b - a

  24. 	}

  25. 	return a - b

  26. }

  27. 

  28. func TestColourBrighten(t *testing.T) {

  29. 	actual := NewColour(128, 128, 128).Brighten(0.5)

  30. 	// Closeish to what we expect is fine.

  31. 	assert.True(t, distance(192, actual.Red()) <= 2)

  32. 	assert.True(t, distance(192, actual.Blue()) <= 2)

  33. 	assert.True(t, distance(192, actual.Green()) <= 2)

  34. 	actual = NewColour(128, 128, 128).Brighten(-0.5)

  35. 	assert.True(t, distance(65, actual.Red()) <= 2)

  36. 	assert.True(t, distance(65, actual.Blue()) <= 2)

  37. 	assert.True(t, distance(65, actual.Green()) <= 2)

  38. }

  39. 

  40. func TestColourBrightess(t *testing.T) {

  41. 	actual := NewColour(128, 128, 128).Brightness()

  42. 	assert.True(t, distance(128, uint8(actual*255.0)) <= 2)

  43. }

  44. 

  45. // hue returns c's hue. See https://stackoverflow.com/a/23094494.

  46. func hue(c Colour) float64 {

  47. 	r := float64(c.Red()) / 255

  48. 	g := float64(c.Green()) / 255

  49. 	b := float64(c.Blue()) / 255

  50. 

  51. 	min := math.Min(math.Min(r, g), b)

  52. 	max := math.Max(math.Max(r, g), b)

  53. 

  54. 	switch {

  55. 	case r == min:

  56. 		return (g - b) / (max - min)

  57. 	case g == min:

  58. 		return 2 + (b-r)/(max-min)

  59. 	default:

  60. 		return 4 + (r-g)/(max-min)

  61. 	}

  62. }

  63. 

  64. func TestColourClampBrightness(t *testing.T) {

  65. 	// Start with a colour with a brightness close to 0.5.

  66. 	initial := NewColour(0, 128, 255)

  67. 	br := initial.Brightness()

  68. 	assertInDelta(t, 0.5, br)

  69. 

  70. 	// Passing a range that includes the colour's brightness should be a no-op.

  71. 	assert.Equal(t, initial.String(), initial.ClampBrightness(br-0.01, br+0.01).String())

  72. 

  73. 	// Clamping to [0, 0] or [1, 1] should produce black or white, respectively.

  74. 	assert.Equal(t, "#000000", initial.ClampBrightness(0, 0).String())

  75. 	assert.Equal(t, "#ffffff", initial.ClampBrightness(1, 1).String())

  76. 

  77. 	// Clamping to a brighter or darker range should produce the requested

  78. 	// brightness while preserving the colour's hue.

  79. 	brighter := initial.ClampBrightness(0.75, 1)

  80. 	assertInDelta(t, 0.75, brighter.Brightness())

  81. 	assertInDelta(t, hue(initial), hue(brighter))

  82. 

  83. 	darker := initial.ClampBrightness(0, 0.25)

  84. 	assertInDelta(t, 0.25, darker.Brightness())

  85. 	assertInDelta(t, hue(initial), hue(darker))

  86. }

  87. 

  88. func assertInDelta(t *testing.T, expected, actual float64) {

  89. 	const delta = 0.01 // used for brightness and hue comparisons

  90. 	assert.True(t, actual > (expected-delta) && actual < (expected+delta))

  91. }
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