114 lines
2.4 KiB
Go
114 lines
2.4 KiB
Go
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package main
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import (
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"bytes"
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b64 "encoding/base64"
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"encoding/hex"
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"image"
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"image/color"
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_ "image/jpeg"
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"image/png"
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"log"
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"syscall/js"
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"time"
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"github.com/makeworld-the-better-one/dither/v2"
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)
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var nordPalette, _ = buildPalette([]string{
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"2e3440",
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"3b4252",
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"434c5e",
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"4c566a",
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"d8dee9",
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"e5e9f0",
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"eceff4",
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"8fbcbb",
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"88c0d0",
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"81a1c1",
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"5e81ac",
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"bf616a",
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"d08770",
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"ebcb8b",
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"a3be8c",
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"b48ead",
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})
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func buildPalette(pal []string) (color.Palette, error) {
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var palette = make(color.Palette, len(pal))
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for i, s := range pal {
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b, err := hex.DecodeString(s)
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if err != nil {
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return nil, err
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}
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palette[i] = color.RGBA{b[0], b[1], b[2], 0xff}
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}
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return palette, nil
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}
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func ditherImage(img image.Image) image.Image {
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// Build ditherer
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ditherer := dither.NewDitherer(nordPalette)
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ditherer.Matrix = dither.FloydSteinberg
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// Dither image in a copy
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dst := ditherer.DitherCopy(img)
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return dst
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}
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func decodeImage(imageData []byte) (image.Image, error) {
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img, imageType, err := image.Decode(bytes.NewReader(imageData))
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if err != nil {
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return nil, err
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}
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log.Printf("Decoded image as %v\n", imageType)
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return img, nil
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}
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// DittherNord returns a Promise that takes a UintArray containing a Jpeg or png image,
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// and resolves to a string containing a base64 encoded png image.
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func DitherNord() js.Func {
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return js.FuncOf(func(this js.Value, args []js.Value) interface{} {
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imageBytes := make([]byte, args[0].Length())
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js.CopyBytesToGo(imageBytes, args[0])
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handler := js.FuncOf(func(this js.Value, args []js.Value) interface{} {
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resolve := args[0]
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reject := args[1]
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go func() {
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// Decode image from raw bytes
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img, err := decodeImage(imageBytes)
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if err != nil {
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errorConstructor := js.Global().Get("Error")
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errorObject := errorConstructor.New(err.Error())
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reject.Invoke(errorObject)
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}
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// Perform dithering
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log.Println("Dithering image...")
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t1 := time.Now()
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ditheredImage := ditherImage(img)
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t2 := time.Now()
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log.Printf("Image dithered in %v\n", t2.Sub(t1))
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// Encode as PNG
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buf := new(bytes.Buffer)
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png.Encode(buf, ditheredImage)
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// Encode as img src b64 string and resolve
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encodedImage := b64.StdEncoding.EncodeToString(buf.Bytes())
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resolve.Invoke(js.ValueOf(encodedImage))
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}()
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return nil
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})
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promiseConstructor := js.Global().Get("Promise")
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return promiseConstructor.New(handler)
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})
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}
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