colorgrad

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

Support This Project

Index

Custom Gradient
Preset Gradients
Using the Gradient
Examples
Playground

import "github.com/mazznoer/colorgrad"

Custom Gradient

Basic

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

Custom Colors

grad, err := colorgrad.NewGradient().
    Colors(
        colorgrad.Rgb8(0, 206, 209, 255),
        colorgrad.Rgb8(255, 105, 180, 255),
        colorgrad.Rgb(0.274, 0.5, 0.7, 1),
        colorgrad.Hsv(50, 1, 1, 1),
        colorgrad.Hsv(348, 0.9, 0.8, 1),
    ).
    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()

blend-modes

Interpolation Mode

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

InterpolationLinear
interpolation-linear

InterpolationCatmullRom
interpolation-catmull-rom

InterpolationBasis
interpolation-basis

Preset Gradients

See PRESET.md

Parsing GIMP Gradient

import "os"
foreground := colorgrad.Rgb(0, 0, 0, 1)
background := colorgrad.Rgb(1, 1, 1, 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

gimp-gradient

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

Get n colors evenly spaced across gradient

grad := colorgrad.Rainbow()
for _, c := range grad.Colors(10) {
    fmt.Println(c.HexString())
}

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.

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)
}