70 lines
1.8 KiB
TypeScript
70 lines
1.8 KiB
TypeScript
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import Jimp from 'npm:jimp@0.22.8'
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function floydSteinberg (data: Buffer, w: number, h: number) {
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const errorMultiplier = .6 // 1 is normal, 0.5 is "reduced color bleeding"
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const filter = [
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[0, 0, 0, 7 / 48, 5 / 48],
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[3 / 48, 5 / 48, 7 / 48, 5 / 48, 3 / 48],
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[1 / 48, 3 / 48, 5 / 48, 3 / 48, 1 / 48]
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]
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const error = Array(h)
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let r: number
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let g: number
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let b: number
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for (let y = 0; y < h; y++) error[y] = new Float32Array(w)
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for (let y = 0; y < h; y++) {
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for (let x = 0; x < w; x++) {
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const id = ((y * w) + x) * 4
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r = data[id]
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g = data[id + 1]
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b = data[id + 2]
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let avg = (r + g + b) / 3
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avg -= error[y][x] * errorMultiplier
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let e = 0
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if (avg < 128) {
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e = -avg
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avg = 0
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} else {
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e = 255 - avg
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avg = 255
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}
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data[id] = data[id + 1] = data[id + 2] = avg
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data[id + 3] = 255
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for (let yy = 0; yy < 3; yy++) {
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for (let xx = -2; xx <= 2; xx++) {
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if (y + yy < 0 || h <= y + yy || x + xx < 0 || w <= x + xx) continue
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error[y + yy][x + xx] += e * filter[yy][xx + 2]
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}
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}
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}
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}
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return data
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}
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export default async function process (source: string, destinationWidth?: number, destinationHeight?: number, storeAs?: string): Uint8ClampedArray | null {
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try {
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const image = await Jimp.read(source)
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const width = destinationWidth ?? image.bitmap.width
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const height = destinationHeight ?? image.bitmap.height
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image.grayscale().cover(width, height)
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const data = floydSteinberg(image.bitmap.data, width, height)
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if (storeAs) {
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new Jimp({data, width, height }, (err, image) => image.write(storeAs))
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}
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return new Uint8ClampedArray(data)
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} catch (error) {
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console.error('failed to process image', error)
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return null
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}
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}
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