82 lines
1.9 KiB
Go
82 lines
1.9 KiB
Go
package main
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import (
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"image"
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"math"
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"github.com/mattn/go-ciede2000"
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)
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// Maps RGB colors to the eink display's color values
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type ColorSpace []struct {
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Color Colorf
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Code uint8
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}
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func ditherPixel(image [][]Colorf, x int, y int, diff Colorf) {
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height := len(image)
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width := len(image[0])
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if x < 0 || y < 0 || x >= width || y >= height {
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return
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}
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image[y][x] = clampColor(addColorf(image[y][x], diff), 0, 1)
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}
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func ditherFloydSteinberg(image [][]Colorf, x int, y int, color Colorf) {
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ditherPixel(image, x+1, y, multColor(color, 7.0/16.0))
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ditherPixel(image, x-1, y+1, multColor(color, 3.0/16.0))
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ditherPixel(image, x, y+1, multColor(color, 5.0/16.0))
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ditherPixel(image, x+1, y+1, multColor(color, 1.0/16.0))
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}
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func ConvertToEInkImage(src image.Image, colorSpace ColorSpace) []byte {
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bounds := src.Bounds()
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width, height := bounds.Max.X, bounds.Max.Y
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image := convertImageToColors(src)
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var einkImage []byte
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for y := 0; y < height; y++ {
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for x := 0; x < width; x++ {
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// find closest color
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minDist := math.MaxFloat64
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bestColorCode := uint8(0x0)
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bestColor := Colorf{0, 0, 0}
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for _, def := range colorSpace {
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dist := ciede2000.Diff(convertToRGBA(image[y][x]), convertToRGBA(def.Color))
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if dist < minDist {
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minDist = dist
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bestColorCode = def.Code
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bestColor = def.Color
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}
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}
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einkImage = append(einkImage, byte(bestColorCode))
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// dither the remaining color using Floyd-Steinberg to create the illusion of shading
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diff := subtractColorf(image[y][x], bestColor)
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ditherFloydSteinberg(image, x, y, diff)
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}
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}
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// each byte holds two pixels for eink display
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einkImage = packBytesIntoNibbles(einkImage)
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return einkImage
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}
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func packBytesIntoNibbles(input []byte) []byte {
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// input length must divisible by 2
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var output []byte
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for x := 0; x < len(input); x += 2 {
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output = append(output, (input[x]<<4)|input[x+1])
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}
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return output
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}
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