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https://github.com/mazznoer/colorgrad

Go (Golang) color scales library for maps, charts, data-visualization & creative coding.
https://github.com/mazznoer/colorgrad

color color-scales colormap data-visualization gradient visual-encoding visualization

Last synced: 3 months ago
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Go (Golang) color scales library for maps, charts, data-visualization & creative coding.

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# colorgrad



[![Release](https://img.shields.io/github/release/mazznoer/colorgrad.svg)](https://github.com/mazznoer/colorgrad/releases/latest)

[![PkgGoDev](https://pkg.go.dev/badge/github.com/mazznoer/colorgrad)](https://pkg.go.dev/github.com/mazznoer/colorgrad)

![Build Status](https://github.com/mazznoer/colorgrad/actions/workflows/go.yml/badge.svg)

[![go report](https://goreportcard.com/badge/github.com/mazznoer/colorgrad)](https://goreportcard.com/report/github.com/mazznoer/colorgrad)



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



## Support This Project



[![Donate](https://liberapay.com/assets/widgets/donate.svg)](https://liberapay.com/mazznoer/donate)



## Index



* [Custom Gradient](#custom-gradient)

* [Preset Gradients](#preset-gradients)

* [Using the Gradient](#using-the-gradient)

* [Examples](#examples)

* [Playground](#playground)



```go

import "github.com/mazznoer/colorgrad"

```



## Custom Gradient



### Basic



```go

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

```

![img](doc/images/custom-default.png)



### Custom Colors



```go

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()

```

![img](doc/images/custom-colors.png)



### Using Web Color Format



`HtmlColors()` method accepts [named colors](https://www.w3.org/TR/css-color-4/#named-colors), hexadecimal (`#rgb`, `#rgba`, `#rrggbb`, `#rrggbbaa`), `rgb()`, `rgba()`, `hsl()`, `hsla()`, `hwb()`, and `hsv()`.



```go

grad, err := colorgrad.NewGradient().

    HtmlColors("#C41189", "#00BFFF", "#FFD700").

    Build()

```

![img](doc/images/custom-hex-colors.png)



```go

grad, err := colorgrad.NewGradient().

    HtmlColors("gold", "hotpink", "darkturquoise").

    Build()

```

![img](doc/images/custom-named-colors.png)



```go

grad, err := colorgrad.NewGradient().

    HtmlColors(

        "rgb(125,110,221)",

        "rgb(90%,45%,97%)",

        "hsl(229,79%,85%)",

    ).

    Build()

```

![img](doc/images/custom-css-colors.png)



### Domain & Color Position



Default domain is [0..1].



```go

grad, err := colorgrad.NewGradient().

    HtmlColors("deeppink", "gold", "seagreen").

    Build()

```

![img](https://raw.githubusercontent.com/mazznoer/colorgrad-rs/master/docs/images/domain-default.png)



Set the domain to [0..100].



```go

grad, err := colorgrad.NewGradient().

    HtmlColors("deeppink", "gold", "seagreen").

    Domain(0, 100).

    Build()

```

![img](https://raw.githubusercontent.com/mazznoer/colorgrad-rs/master/docs/images/domain-100.png)



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



```go

grad, err := colorgrad.NewGradient().

    HtmlColors("deeppink", "gold", "seagreen").

    Domain(-1, 1).

    Build()

```

![img](https://raw.githubusercontent.com/mazznoer/colorgrad-rs/master/docs/images/domain-neg1-1.png)



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



```go

grad, err := colorgrad.NewGradient().

    HtmlColors("deeppink", "gold", "seagreen").

    Domain(0, 0.7, 1).

    Build()

```

![img](https://raw.githubusercontent.com/mazznoer/colorgrad-rs/master/docs/images/color-position-1.png)



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



```go

grad, err := colorgrad.NewGradient().

    HtmlColors("deeppink", "gold", "seagreen").

    Domain(15, 30, 80).

    Build()

```

![img](https://raw.githubusercontent.com/mazznoer/colorgrad-rs/master/docs/images/color-position-2.png)



### Blending Mode



```go

grad, err := colorgrad.NewGradient().

    HtmlColors("#FFF", "#00F").

    Mode(colorgrad.BlendRgb).

    Build()

```

![blend-modes](doc/images/blend-modes-2.png)



### Interpolation Mode



```go

grad, err := colorgrad.NewGradient().

    HtmlColors("#C41189", "#00BFFF", "#FFD700").

    Interpolation(colorgrad.InterpolationLinear).

    Build()

```



`InterpolationLinear`

![interpolation-linear](doc/images/interpolation-linear.png)



`InterpolationCatmullRom`

![interpolation-catmull-rom](doc/images/interpolation-catmull-rom.png)



`InterpolationBasis`

![interpolation-basis](doc/images/interpolation-basis.png)



## Preset Gradients



See [PRESET.md](PRESET.md)



## Parsing GIMP Gradient



```go

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](doc/images/ggr-abstract-1.png)



## Using the Gradient



### Get the domain



```go

grad := colorgrad.Rainbow()



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

```



### Get single color at certain position



```go

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



```go

grad := colorgrad.Rainbow()



for _, c := range grad.Colors(10) {

    fmt.Println(c.HexString())

}

```



Output:



```console

#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.



```go

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

```

![img](doc/images/rainbow-sharp.png)



This is the effect of different smoothness.



![img](doc/images/sharp-gradients.png)



## Examples



### Gradient Image



```go

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:



![img](doc/images/custom-hex-colors.png)



### Colored Noise



```go

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:



![noise](doc/images/noise.png)



## Playground



* [Basic](https://play.golang.org/p/PlMov8BKfRc)

* [Random colors](https://play.golang.org/p/d67x9di4sAF)



## Dependencies



* [csscolorparser](https://github.com/mazznoer/csscolorparser)



## Inspirations



* [chroma.js](https://gka.github.io/chroma.js/#color-scales)

* [d3-scale-chromatic](https://github.com/d3/d3-scale-chromatic/)

* colorful's [gradientgen.go](https://github.com/lucasb-eyer/go-colorful/blob/master/doc/gradientgen/gradientgen.go)



## Links



* [colorgrad-rs](https://github.com/mazznoer/colorgrad-rs) - Rust port of this library