golor

A Go library for color manipulation, conversion, and accessibility.

go get github.com/0mega24/golor

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Overview

golor provides a single Color type (normalized sRGB) and a set of focused sub-packages for everything you might need to do with colors in Go.

Package	What it does
golor	Core type, constructors, hex parsing
convert	HSL, HSV, L*a*b*, LCH conversions
adjust	Lighten, darken, saturate, hue shift, warm/cool, tint, shade
blend	Blend modes: multiply, screen, overlay, soft light, and more
contrast	WCAG 2.1 contrast ratio and enforcement
deltae	Perceptual color difference (dE76 and CIEDE2000)
colorblind	Deficiency simulation and accessible palette generation
harmony	Complementary, triadic, analogous, tetradic, split schemes
gradient	Interpolation in RGB, HSL, L*a*b*, and LCH
transform	Fluent chained transformations

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Usage

Creating colors

import "github.com/0mega24/golor"

c := golor.RGB(255, 107, 53)       // from 8-bit channels
c := golor.RGBf(1.0, 0.42, 0.21)  // from normalized floats
c, err := golor.Hex("#ff6b35")     // from hex string

fmt.Println(c) // #ff6b35

Adjusting colors

import "github.com/0mega24/golor/adjust"

lighter  := adjust.Lighten(c, 0.1)
darker   := adjust.Darken(c, 0.1)
vibrant  := adjust.Saturate(c, 0.2)
muted    := adjust.Desaturate(c, 0.2)
shifted  := adjust.ShiftHue(c, 30)
warmer   := adjust.Warm(c, 0.3)
cooler   := adjust.Cool(c, 0.3)
tinted   := adjust.Tint(c, 0.2)   // toward white
shaded   := adjust.Shade(c, 0.2)  // toward black

Fluent chaining

import "github.com/0mega24/golor/transform"

result := transform.From(c).
    Lighten(0.1).
    Saturate(0.2).
    Warm(0.15).
    Color()

Color space conversions

import "github.com/0mega24/golor/convert"

hsl := convert.ToHSL(c)   // HSL{H:16, S:1.0, L:0.6}
hsv := convert.ToHSV(c)
lab := convert.ToLAB(c)
lch := convert.ToLCH(c)

back := convert.FromLCH(lch) // round-trips cleanly

Blend modes

import "github.com/0mega24/golor/blend"

out := blend.Multiply(base, layer)
out  = blend.Screen(base, layer)
out  = blend.Overlay(base, layer)
out  = blend.SoftLight(base, layer)
out  = blend.Mix(base, layer, 0.5) // linear interpolation

Contrast and accessibility

import "github.com/0mega24/golor/contrast"

r := contrast.Ratio(fg, bg)         // e.g. 4.87
ok := contrast.Meets(fg, bg, 4.5)   // WCAG AA

// Adjust fg until it meets the threshold against bg
fg = contrast.EnforceContrast(fg, bg, 4.5)

Perceptual color difference

import "github.com/0mega24/golor/deltae"

d76   := deltae.DeltaE76(c1, c2)    // fast, CIE 1976
d2000 := deltae.DeltaE2000(c1, c2)  // accurate, CIEDE2000

// Nudge palette entries apart until each pair differs by at least minDeltaE
palette = deltae.EnsureDistinct(palette, 10.0)

Colorblind simulation

import "github.com/0mega24/golor/colorblind"

sim := colorblind.Simulate(c, colorblind.Deuteranopia)
sim  = colorblind.Simulate(c, colorblind.Protanopia)
sim  = colorblind.Simulate(c, colorblind.Tritanopia)

// Shift palette hues until distinguishable under the given deficiency
safe := colorblind.AccessiblePalette(palette, colorblind.Deuteranopia)

Color harmonies

import "github.com/0mega24/golor/harmony"

pair    := harmony.Complementary(c)        // [2]Color
triad   := harmony.Triadic(c)             // [3]Color
quad    := harmony.Tetradic(c)            // [4]Color
analog  := harmony.Analogous(c)           // [3]Color
split   := harmony.SplitComplementary(c)  // [3]Color
shades  := harmony.Expand(c, 5)           // []Color, lightness spread

Gradients

import "github.com/0mega24/golor/gradient"

steps := gradient.RGB(black, white, 10)   // []Color, RGB interpolation
steps  = gradient.HSL(red, blue, 10)      // hue takes shortest path
steps  = gradient.LCH(red, blue, 10)      // perceptually uniform
steps  = gradient.LAB(red, blue, 10)

// Multi-stop
stops  := []golor.Color{black, red, yellow, white}
ramp   := gradient.MultiStopLCH(stops, 64)

---

Development

make test      # run tests with race detector
make lint      # run golangci-lint
make fmt       # format with gofumpt
make fix       # auto-fix lint issues where possible
make vet       # run go vet

Requires golangci-lint and gofumpt to be installed for lint and fmt.

See CONTRIBUTING.md for full contribution guidelines.

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License

Apache 2.0, see LICENSE.