label_printer/escpos/rasterize.go

// This file was origionally from:
// https://github.com/mugli/png2escpos/blob/56fca745daa0149280e04b5155cb59f1796e8842/escpos/raster.go
//
// Copyright (c) 2019, Mehdi Hasan Khan
//
// Permission is hereby granted, free of charge, to any person obtaining a copy of
// this software and associated documentation files (the "Software"), to deal in
// the Software without restriction, including without limitation the rights to
// use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
// the Software, and to permit persons to whom the Software is furnished to do so,
// subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in all
// copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
// FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
// COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
// IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
// CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
//
// And adapted at:
// https://github.com/hennedo/escpos/blob/475ba147a030cd572bd9137e62a55185238738aa/bitimage.go
//
// MIT License
//
// Copyright (c) 2021 Hendrik Fellerhoff
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions
//
// The above copyright notice and this permission notice shall be included in all
// copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
// SOFTWARE.

package escpos

import (
	"fmt"
	"image"
)

func closestNDivisibleBy8(n int) int {
	q := n / 8
	n1 := q * 8

	return n1
}

func getPrintImageData(img image.Image) (x int, y int, data []byte) {
	width, height, pixels := getPixels(img)

	removeTransparency(&pixels)
	makeGrayscale(&pixels)

	printWidth := closestNDivisibleBy8(width)
	printHeight := closestNDivisibleBy8(height)
	bytes, _ := rasterize(printWidth, printHeight, &pixels)

	return printWidth, printHeight, bytes
}

func makeGrayscale(pixels *[][]pixel) {
	height := len(*pixels)
	width := len((*pixels)[0])

	for y := 0; y < height; y++ {
		row := (*pixels)[y]
		for x := 0; x < width; x++ {
			pixel := row[x]

			luminance := (float64(pixel.R) * 0.299) + (float64(pixel.G) * 0.587) + (float64(pixel.B) * 0.114)
			var value int
			if luminance < 128 {
				value = 0
			} else {
				value = 255
			}

			pixel.R = value
			pixel.G = value
			pixel.B = value

			row[x] = pixel
		}
	}
}

func removeTransparency(pixels *[][]pixel) {
	height := len(*pixels)
	width := len((*pixels)[0])

	for y := 0; y < height; y++ {
		row := (*pixels)[y]
		for x := 0; x < width; x++ {
			pixel := row[x]

			alpha := pixel.A
			invAlpha := 255 - alpha

			pixel.R = (alpha*pixel.R + invAlpha*255) / 255
			pixel.G = (alpha*pixel.G + invAlpha*255) / 255
			pixel.B = (alpha*pixel.B + invAlpha*255) / 255
			pixel.A = 255

			row[x] = pixel
		}
	}
}

func rasterize(printWidth int, printHeight int, pixels *[][]pixel) ([]byte, error) {
	if printWidth%8 != 0 {
		return nil, fmt.Errorf("printWidth must be a multiple of 8")
	}

	if printHeight%8 != 0 {
		return nil, fmt.Errorf("printHeight must be a multiple of 8")
	}

	bytes := make([]byte, (printWidth*printHeight)>>3)

	for y := 0; y < printHeight; y++ {
		for x := 0; x < printWidth; x = x + 8 {
			i := y*(printWidth>>3) + (x >> 3)
			bytes[i] =
				byte((getPixelValue(x+0, y, pixels) << 7) |
					(getPixelValue(x+1, y, pixels) << 6) |
					(getPixelValue(x+2, y, pixels) << 5) |
					(getPixelValue(x+3, y, pixels) << 4) |
					(getPixelValue(x+4, y, pixels) << 3) |
					(getPixelValue(x+5, y, pixels) << 2) |
					(getPixelValue(x+6, y, pixels) << 1) |
					getPixelValue(x+7, y, pixels))
		}
	}

	return bytes, nil
}

func getPixelValue(x int, y int, pixels *[][]pixel) int {
	row := (*pixels)[y]
	pixel := row[x]

	if pixel.R > 0 {
		return 0
	}

	return 1
}

func rgbaToPixel(r uint32, g uint32, b uint32, a uint32) pixel {
	return pixel{int(r >> 8), int(g >> 8), int(b >> 8), int(a >> 8)}
}

type pixel struct {
	R int
	G int
	B int
	A int
}

func getPixels(img image.Image) (int, int, [][]pixel) {

	bounds := img.Bounds()
	width, height := bounds.Max.X, bounds.Max.Y

	var pixels [][]pixel
	for y := 0; y < height; y++ {
		var row []pixel
		for x := 0; x < width; x++ {
			row = append(row, rgbaToPixel(img.At(x, y).RGBA()))
		}
		pixels = append(pixels, row)
	}

	return width, height, pixels
}