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const PNG = require('pngjs').PNG | ||
const fs = require('fs') | ||
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const mode = (array) => { | ||
const map = new Map(); | ||
let maxFreq = 0; | ||
let mode; | ||
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for(const item of array) { | ||
let freq = map.has(item) ? map.get(item) : 0; | ||
freq++; | ||
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if(freq > maxFreq) { | ||
maxFreq = freq; | ||
mode = item; | ||
} | ||
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map.set(item, freq); | ||
} | ||
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return mode; | ||
}; | ||
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function getPngPixels(pngBuffer) { | ||
const png = PNG.sync.read(pngBuffer) | ||
return { | ||
depth: 4, | ||
order: 'rgba', | ||
width: png.width, | ||
height: png.height, | ||
data: Uint8ClampedArray.from(png.data) | ||
} | ||
} | ||
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function computeDelta(before, after) { | ||
const delta = new Uint8ClampedArray(before.data.length) | ||
for (let i = 0; i !== before.data.length / 4; ++i) { | ||
const brightnessBefore = 0.2126 * before.data[4*i] + 0.7152 * before.data[4*i+1] + 0.0722 * before.data[4*i+2] | ||
const brightnessAfter = 0.2126 * after.data[4*i] + 0.7152 * after.data[4*i+1] + 0.0722 * after.data[4*i+2] | ||
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delta[4*i] = Math.abs(brightnessBefore - brightnessAfter) | ||
delta[4*i+1] = Math.abs(brightnessBefore - brightnessAfter) | ||
delta[4*i+2] = Math.abs(brightnessBefore - brightnessAfter) | ||
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delta[4*i+3] = 255 | ||
} | ||
return { | ||
data: delta, | ||
colorType: 6, | ||
depth: 4, | ||
width: before.width, | ||
height: before.height | ||
} | ||
} | ||
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function binarize(delta, THRESHOLD = 0x40) { | ||
function getXY(x, y) { | ||
const pos = y * delta.width + x | ||
return delta.data[4 * pos] | ||
} | ||
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function binarizePixel(val) { | ||
return val > THRESHOLD ? 255 : 0 | ||
} | ||
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const ret = new Uint8ClampedArray(delta.data.length) | ||
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// pool surrounding pixels | ||
for (let y = 0; y !== delta.height; ++y) { | ||
for (let x = 0; x !== delta.width; ++x) { | ||
const vals = [] | ||
const SURROUNDING = 3 | ||
// get surrounding pixels | ||
for (let i = -SURROUNDING; i <= SURROUNDING; ++i) { | ||
for (let j = -SURROUNDING; j <= SURROUNDING; ++j) { | ||
vals.push(getXY(x+i, y+j)) | ||
} | ||
} | ||
const polledResult = Math.max(...vals) | ||
const pixelPos = y * delta.width + x | ||
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ret[pixelPos * 4] = binarizePixel(polledResult) | ||
ret[pixelPos * 4 + 1] = binarizePixel(polledResult) | ||
ret[pixelPos * 4 + 2] = binarizePixel(polledResult) | ||
ret[pixelPos * 4 + 3] = 255 // alpha channel | ||
} | ||
} | ||
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return { | ||
data: ret, | ||
colorType: 6, | ||
depth: 4, | ||
width: delta.width, | ||
height: delta.height | ||
} | ||
} | ||
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function locate(binaryMap, GAP_THRESHOLD = 10) { | ||
const { | ||
data, | ||
width, | ||
height | ||
} = binaryMap | ||
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function getXY(x, y) { | ||
const pos = y * width + x | ||
return data[pos * 4] | ||
} | ||
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const offsets = [] | ||
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// scan from right | ||
for (let y = 0; y !== height; ++y) { | ||
let observations = [] | ||
let rightPos = -1 | ||
let leftPos = -1 | ||
let rightDetected = false | ||
for (let x = width - 1; x >= 0; --x) { | ||
const val = getXY(x, y) | ||
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observations.push(val) | ||
observations.length > GAP_THRESHOLD && observations.shift() | ||
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// check for right rect's right edge | ||
if (rightPos === -1 && val === 0xff) { | ||
rightPos = x | ||
} | ||
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// check for left rect's left edge | ||
if ( rightPos >= 0 | ||
&& observations.length === GAP_THRESHOLD | ||
&& observations.filter(ob => ob === 0).length === GAP_THRESHOLD | ||
) { | ||
rightDetected = true | ||
} | ||
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if (rightDetected && leftPos === -1 && val === 0xff) { | ||
leftPos = x | ||
offsets.push(rightPos - leftPos) | ||
break | ||
} | ||
} | ||
} | ||
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// get mode of X | ||
return mode(offsets) | ||
} | ||
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module.exports = function deltaLocate(sourcePixels, knobPixels) { | ||
const delta = computeDelta(sourcePixels, knobPixels) | ||
const binaryDelta = binarize(delta) | ||
const xPos = locate(binaryDelta) | ||
return xPos | ||
} |