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package chroma
import (
"math"
"testing"
assert "github.com/alecthomas/assert/v2"
)
func TestColourRGB(t *testing.T) {
colour := ParseColour("#8913af")
assert.Equal(t, uint8(0x89), colour.Red())
assert.Equal(t, uint8(0x13), colour.Green())
assert.Equal(t, uint8(0xaf), colour.Blue())
}
func TestColourString(t *testing.T) {
assert.Equal(t, "#8913af", ParseColour("#8913af").String())
}
func distance(a, b uint8) uint8 {
if a < b {
return b - a
}
return a - b
}
func TestColourBrighten(t *testing.T) {
actual := NewColour(128, 128, 128).Brighten(0.5)
// Closeish to what we expect is fine.
assert.True(t, distance(192, actual.Red()) <= 2)
assert.True(t, distance(192, actual.Blue()) <= 2)
assert.True(t, distance(192, actual.Green()) <= 2)
actual = NewColour(128, 128, 128).Brighten(-0.5)
assert.True(t, distance(65, actual.Red()) <= 2)
assert.True(t, distance(65, actual.Blue()) <= 2)
assert.True(t, distance(65, actual.Green()) <= 2)
}
func TestColourBrightess(t *testing.T) {
actual := NewColour(128, 128, 128).Brightness()
assert.True(t, distance(128, uint8(actual*255.0)) <= 2)
}
// hue returns c's hue. See https://stackoverflow.com/a/23094494.
func hue(c Colour) float64 {
r := float64(c.Red()) / 255
g := float64(c.Green()) / 255
b := float64(c.Blue()) / 255
min := math.Min(math.Min(r, g), b)
max := math.Max(math.Max(r, g), b)
switch {
case r == min:
return (g - b) / (max - min)
case g == min:
return 2 + (b-r)/(max-min)
default:
return 4 + (r-g)/(max-min)
}
}
func TestColourClampBrightness(t *testing.T) {
// Start with a colour with a brightness close to 0.5.
initial := NewColour(0, 128, 255)
br := initial.Brightness()
assertInDelta(t, 0.5, br)
// Passing a range that includes the colour's brightness should be a no-op.
assert.Equal(t, initial.String(), initial.ClampBrightness(br-0.01, br+0.01).String())
// Clamping to [0, 0] or [1, 1] should produce black or white, respectively.
assert.Equal(t, "#000000", initial.ClampBrightness(0, 0).String())
assert.Equal(t, "#ffffff", initial.ClampBrightness(1, 1).String())
// Clamping to a brighter or darker range should produce the requested
// brightness while preserving the colour's hue.
brighter := initial.ClampBrightness(0.75, 1)
assertInDelta(t, 0.75, brighter.Brightness())
assertInDelta(t, hue(initial), hue(brighter))
darker := initial.ClampBrightness(0, 0.25)
assertInDelta(t, 0.25, darker.Brightness())
assertInDelta(t, hue(initial), hue(darker))
}
func assertInDelta(t *testing.T, expected, actual float64) {
const delta = 0.01 // used for brightness and hue comparisons
assert.True(t, actual > (expected-delta) && actual < (expected+delta))
}
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