colorgrad 🎨

Go (Golang) color scales library for data visualization, charts, games, maps, generative art and others.

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Index

• Custom Gradient
• Preset Gradients
• Using the Gradient
• Color Schemes
• Examples
• Playground

import "github.com/mazznoer/colorgrad"

Custom Gradient

Basic

grad, err := colorgrad.NewGradient().Build()

Custom Colors

Colors() method accept anything that implement color.Color interface.

import "image/color"
import "github.com/lucasb-eyer/go-colorful"

grad, err := colorgrad.NewGradient().
    Colors(
        color.RGBA{0, 206, 209, 255},
        color.RGBA{255, 105, 180, 255},
        colorful.Color{R: 0.274, G: 0.5, B: 0.7},
        colorful.Hsv(50, 1, 1),
        colorful.Hsv(348, 0.9, 0.8),
    ).
    Build()

Using Web Color Format

HtmlColors() method accepts named colors, hexadecimal (#rgb, #rgba, #rrggbb, #rrggbbaa), rgb(), rgba(), hsl(), hsla(), hwb(), and hsv().

grad, err := colorgrad.NewGradient().
    HtmlColors("#C41189", "#00BFFF", "#FFD700").
    Build()

grad, err := colorgrad.NewGradient().
    HtmlColors("gold", "hotpink", "darkturquoise").
    Build()

grad, err := colorgrad.NewGradient().
    HtmlColors(
        "rgb(125,110,221)",
        "rgb(90%,45%,97%)",
        "hsl(229,79%,85%)",
    ).
    Build()

Domain & Color Position

Default domain is [0..1].

grad, err := colorgrad.NewGradient().
    HtmlColors("deeppink", "gold", "seagreen").
    Build()

Set the domain to [0..100].

grad, err := colorgrad.NewGradient().
    HtmlColors("deeppink", "gold", "seagreen").
    Domain(0, 100).
    Build()

Set the domain to [-1..1].

grad, err := colorgrad.NewGradient().
    HtmlColors("deeppink", "gold", "seagreen").
    Domain(-1, 1).
    Build()

Set exact position for each color. The domain is [0..1].

grad, err := colorgrad.NewGradient().
    HtmlColors("deeppink", "gold", "seagreen").
    Domain(0, 0.7, 1).
    Build()

Set exact position for each color. The domain is [15..80].

grad, err := colorgrad.NewGradient().
    HtmlColors("deeppink", "gold", "seagreen").
    Domain(15, 30, 80).
    Build()

Blending Mode

grad, err := colorgrad.NewGradient().
    HtmlColors("#FFF", "#00F").
    Mode(colorgrad.BlendRgb).
    Build()

Interpolation Mode

grad, err := colorgrad.NewGradient().
    HtmlColors("#C41189", "#00BFFF", "#FFD700").
    Interpolation(colorgrad.InterpolationLinear).
    Build()

InterpolationLinear

InterpolationCatmullRom

InterpolationBasis

Preset Gradients

All preset gradients are in the domain [0..1].

Diverging

colorgrad.BrBG()

colorgrad.PRGn()

colorgrad.PiYG()

colorgrad.PuOr()

colorgrad.RdBu()

colorgrad.RdGy()

colorgrad.RdYlBu()

colorgrad.RdYlGn()

colorgrad.Spectral()

Sequential (Single Hue)

colorgrad.Blues()

colorgrad.Greens()

colorgrad.Greys()

colorgrad.Oranges()

colorgrad.Purples()

colorgrad.Reds()

Sequential (Multi-Hue)

colorgrad.Turbo()

colorgrad.Viridis()

colorgrad.Inferno()

colorgrad.Magma()

colorgrad.Plasma()

colorgrad.Cividis()

colorgrad.Warm()

colorgrad.Cool()

colorgrad.CubehelixDefault()

colorgrad.BuGn()

colorgrad.BuPu()

colorgrad.GnBu()

colorgrad.OrRd()

colorgrad.PuBuGn()

colorgrad.PuBu()

colorgrad.PuRd()

colorgrad.RdPu()

colorgrad.YlGnBu()

colorgrad.YlGn()

colorgrad.YlOrBr()

colorgrad.YlOrRd()

Cyclical

colorgrad.Rainbow()

colorgrad.Sinebow()

Parsing GIMP Gradient

import "os"
import "github.com/lucasb-eyer/go-colorful"

foreground := colorful.Color{R: 0, G: 0, B: 0}
background := colorful.Color{R: 1, G: 1, B: 1}
file, err := os.Open("Abstract_1.ggr")

if err != nil {
	panic(err)
}

defer file.Close()
grad, name, err2 := colorgrad.ParseGgr(file, foreground, background)
fmt.Println(name) // Abstract 1

Using the Gradient

Get the domain

grad := colorgrad.Rainbow()

fmt.Println(grad.Domain()) // 0 1

Get single color at certain position

grad := colorgrad.Rainbow()

fmt.Println(grad.At(0.0).Hex()) // #6e40aa
fmt.Println(grad.At(0.5).Hex()) // #aff05b
fmt.Println(grad.At(1.0).Hex()) // #6e40aa

Get n colors evenly spaced across gradient

.Colors() will return []color.Color.

grad := colorgrad.Rainbow()

for _, c := range grad.Colors(7) {
    fmt.Println(c)
}

Output:

{0.43021004989867906 0.25023866753368473 0.6663314402976028}
{0.9324699655386229 0.2641323667713124 0.5856493589115485}
{1 0.5479694546462268 0.220207078599215}
{0.68717707266999 0.9403236324800919 0.355050281779196}
{0.36562500000000014 0.9182994327976323 0.5525738542381139}
{0.25 0.589697182728592 0.877839930901789}
{0.4302100498986791 0.2502386675336847 0.6663314402976028}

.ColorfulColors() will return []colorful.Color.

grad := colorgrad.Rainbow()

for _, c := range grad.ColorfulColors(10) {
    fmt.Println(c.Hex())
}

Output:

#6e40aa
#c83dac
#ff5375
#ff8c38
#c9d33a
#7cf659
#5dea8d
#48b8d0
#4775de
#6e40aa

Hard-Edged Gradient

Convert gradient to hard-edged gradient with 11 segments and 0 smoothness.

grad := colorgrad.Rainbow().Sharp(11, 0)

This is the effect of different smoothness.

Color Schemes

import "github.com/mazznoer/colorgrad/scheme"

scheme.Category10

scheme.Accent

scheme.Dark2

scheme.Paired

scheme.Pastel1

scheme.Pastel2

scheme.Set1

scheme.Set2

scheme.Set3

scheme.Tableau10

Examples

Gradient Image

package main

import (
    "image"
    "image/png"
    "os"

    "github.com/mazznoer/colorgrad"
)

func main() {
    grad, _ := colorgrad.NewGradient().
        HtmlColors("#C41189", "#00BFFF", "#FFD700").
        Build()

    w := 1500
    h := 70
    fw := float64(w)

    img := image.NewRGBA(image.Rect(0, 0, w, h))

    for x := 0; x < w; x++ {
        col := grad.At(float64(x) / fw)
        for y := 0; y < h; y++ {
            img.Set(x, y, col)
        }
    }

    file, err := os.Create("gradient.png")
    if err != nil {
        panic(err.Error())
    }
    defer file.Close()
    png.Encode(file, img)
}

Example output:

Colored Noise

package main

import (
    "image"
    "image/png"
    "os"

    "github.com/mazznoer/colorgrad"
    "github.com/ojrac/opensimplex-go"
)

func main() {
    w := 600
    h := 350
    scale := 0.02

    grad := colorgrad.Rainbow().Sharp(7, 0.2)
    noise := opensimplex.NewNormalized(996)
    img := image.NewRGBA(image.Rect(0, 0, w, h))

    for y := 0; y < h; y++ {
        for x := 0; x < w; x++ {
            t := noise.Eval2(float64(x)*scale, float64(y)*scale)
            img.Set(x, y, grad.At(t))
        }
    }

    file, err := os.Create("noise.png")
    if err != nil {
        panic(err.Error())
    }
    defer file.Close()
    png.Encode(file, img)
}

Example output:

Playground

• Basic
• Random colors

Dependencies

• colorful
• csscolorparser

Inspirations

• chroma.js
• d3-scale-chromatic
• colorful's gradientgen.go

Links

• colorgrad-rs - Rust port of this library
• https://www.color-blindness.com/coblis-color-blindness-simulator/
• https://github.com/UniStuttgart-VISUS/visual-system-simulator