colour_test.go

Documentation: github.com/alecthomas/chroma/v2

     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  }
    92
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