Go package for working with colours, principally colour extraction and "snap to grid"
Documentation is incomplete.
package main
import (
"context"
"flag"
"image"
_ "image/jpeg"
"log"
"os"
"github.com/aaronland/go-colours/extruder"
"github.com/aaronland/go-colours/grid"
"github.com/aaronland/go-colours/palette"
)
func main() {
flag.Parse()
ctx := context.Background()
ex, _ := extruder.NewExtruder(ctx, "vibrant://")
gr, _ := grid.NewGrid(ctx, "euclidian://")
p, _ := palette.NewPalette(ctx, "css4://")
for _, path := range flag.Args() {
fh, _ := os.Open(path)
im, _, _ := image.Decode(fh)
colours, _ := ex.Colours(ctx, im, 5)
for _, c := range colours {
closest, _ := gr.Closest(ctx, c, p)
for _, cl := range closest {
log.Println(c, cl)
}
}
}
}
Note that error handling has been removed for the sake of brevity.
$> make cli
go build -mod vendor -ldflags="-s -w" -o bin/extrude cmd/extrude/main.go
go build -mod vendor -ldflags="-s -w" -o bin/inspect cmd/inspect/main.go
go build -mod vendor -ldflags="-s -w" -o bin/snap cmd/snap/main.go
go build -mod vendor -ldflags="-s -w" -o bin/review cmd/review/main.go
Command line tool to extrude (derive) dominant colours from one or more images as well as closest matches colours using zero or more "snap-to-grid" colour palettes as JSON-encoded data written to STDOUT.
$> ./bin/extrude -h
Command line tool to extrude (derive) dominant colours from one or more images as well as closest matches colours using zero or more "snap-to-grid" colour palettes as JSON-encoded data written to STDOUT.
Usage:
./bin/extrude [options] uri(N) uri(N)
-allow-remote
Allow fetching remote images (HTTP(S)). (default true)
-extruder-uri value
Zero or more aaronland/go-colours/extruder.Extruder URIs. Default is to use all registered extruder schemes.
-palette-uri value
Zero or more aaronland/go-colours/palette.Palette URIs. Default is to use all registered palette schemes.
-verbose
Enable verbose (debug) logging.
$> ./bin/extrude https://static.sfomuseum.org/media/176/270/453/3/1762704533_jnxsOwjYqsa8RyGsJrYFJvAjnQMe1Nqv_z.jpg | jq
[
{
"uri": "1762704533_jnxsOwjYqsa8RyGsJrYFJvAjnQMe1Nqv_z.png",
"extrusions": [
{
"extruder": "marekm4",
"palettes": [
"crayola",
"css3",
"css4"
],
"swatches": [
{
"colour": {
"name": "b6baa1",
"hex": "#b6baa1",
"reference": "marekm4"
},
"closest": [
{
"palette": "crayola",
"colour": {
"name": "Cadet Blue",
"hex": "#b0b7c6",
"reference": "crayola"
}
},
{
"palette": "css3",
"colour": {
"name": "darkgray",
"hex": "#a9a9a9",
"reference": "css3"
}
},
{
"palette": "css4",
"colour": {
"name": "darkgrey",
"hex": "#a9a9a9",
"reference": "css4"
}
}
]
},
{
"colour": {
"name": "728c9a",
"hex": "#728c9a",
"reference": "marekm4"
},
"closest": [
...and so on
Command line tool to perform colour extraction and "snap-to-grid" matching with one or more colour palettes for images, emitting the results as an HTML page.
$> ./bin/review -h
Command line tool to perform colour extraction and "snap-to-grid" matching with one or more colour palettes for images, emitting the results as an HTML page.
Usage:
./bin/review [options] uri(N) uri(N)
-allow-remote
Allow fetching remote images (HTTP(S)). (default true)
-extruder-uri value
Zero or more aaronland/go-colours/extruder.Extruder URIs. Default is to use all registered extruder schemes.
-palette-uri value
Zero or more aaronland/go-colours/palette.Palette URIs. Default is to use all registered palette schemes.
-root string
The path to a directory where images and HTML files associated with the review should be stored. If empty a new temporary directory will be created (and deleted when the application exits).
-verbose
Enable verbose (debug) logging.
$> ./bin/review https://static.sfomuseum.org/media/176/270/453/3/1762704533_jnxsOwjYqsa8RyGsJrYFJvAjnQMe1Nqv_z.jpg
2025/05/01 17:18:28 INFO Server is ready and features are viewable url=http://localhost:50530
And then when you open your browser to http://localhost:50530 (or whatever address the review tool chooses) you'd see something like this:
Unless you specify a custom -root flag all the images used by the web application (excluding the source images themselves) will be automatically be deleted when you stop the tool.
type Colour interface {
Name() string
Hex() string
Reference() string
Closest() []Colour
AppendClosest(Colour) error // I don't love this... (20180605/thisisaaronland)
String() string
}
type Extruder interface {
Colours(image.Image, int) ([]Colour, error)
Name() string
}
type Grid interface {
Closest(Colour, Palette) (Colour, error)
}
type Palette interface {
Reference() string
Colours() []Colour
}
Extruders are the things that generate a palette of colours for an image.Image.
This returns colours using the marekm4/color-extractor package.
This returns colours using the soniakeys/quant package (specifically the mean.Quantizer).
This returns colours using the vibrant package.
Grids are the things that perform operations or compare colours.
Palettes are a fixed set of colours.
This package exports a WebAssembly binary to export the functionality of the extrude.Extrude function in JavaScript.
This repository contains a pre-compiled extrude.wasm binary (found in the www/wasm folder). If you need or want to recompile the binary the easiest way is to use the handy wasmjs Makefile target:
$> make wasmjs
GOOS=js GOARCH=wasm \
go build -mod vendor -ldflags="-s -w" -tags wasmjs \
-o www/wasm/extrude.wasm \
cmd/extrude-wasm/main.go
For a working example serve the www folder from a web server. I like using the fileserver tool provided by the aaronland/go-http-fileserver package mostly because I wrote it but any old web server will do. For example:
$> fileserver -root www
2025/06/05 10:15:55 Serving www and listening for requests on http://localhost:8080
Open your web browser to http://localhost:8080 you'll see something like this:
You can extract (extrude) colours from a single image on disk. For example:
Or extract (extrude) colours, in real-time, from a video feed. For example:
Under the hood, this is an abbreviated version of what's going on:
function derive_colours(im_b64){
const opts = {
"grid": "euclidian://",
"palettes": [ "crayola://" ],
"extruders": [ "marekm4://" ],
};
const str_opts = JSON.stringify(opts);
// Where im_b64 is a base64-encoded image (NOT a data URI)
colours_extrude(str_opts, im_b64).then((rsp) => {
show_colours(rsp);
}).catch((err) => {
console.log("SAD", err);
});
}
The colours_extrude JavaScript function is the code to extract (extrude) colours which has been exported from the extrude.wasm WebAssembly binary. This example uses the sfomuseum/js-sfomuseum-golang-wasm library for taking care of all the mechanics for loading Go/WebAssembly binaries. For example:
sfomuseum.golang.wasm.fetch("wasm/extrude.wasm").then((rsp) => {
// do something here
}).catch((err) => {
console.error("Failed to load WASM binary", err);
});