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import { rgb2y } from './color-metrics.js'
import { colorOrFallbackColorToRGBA } from './html-color-to-rgba.js'
/** @import {Algorithm} from './color-delta.js' */
export const fallbackAAColor = 'yellow'
export const fallbackDiffColor = 'red'
/**
* @param {object} params - function parameters
* @param {Uint8Array | Uint8ClampedArray} params.img1 - original image
* @param {Uint8Array | Uint8ClampedArray} params.img2 - image to compare
* @param {number} params.width - images width
* @param {number} params.height - images height
* @param {Algorithm} [params.algorithm] - output image
* @returns {{identical: boolean, diffMap: Uint8Array}} number of different pixels
*/
export function getNormalizedDiffs ({ img1, img2, width, height, algorithm = 'CIEDE2000' }) {
validateImagePreconditions({ img1, img2, width, height })
if (!validAlgorithms.includes(algorithm)) { throw new Error(`Invalid algorithm ${algorithm}, expected algorithms: ${validAlgorithms.join(', ')}.`) }
const len = width * height
const diffMap = new Uint8Array(len)
const a32 = new Uint32Array(img1.buffer, img1.byteOffset, len)
const b32 = new Uint32Array(img2.buffer, img2.byteOffset, len)
let identical = true
for (let pixelPos = 0; pixelPos < len; pixelPos++) {
if (a32[pixelPos] === b32[pixelPos]) { continue } // Fast way to check if pixels are identical
const pos = pixelPos * 4
const { delta, maxDelta } = colorDeltaImgPosition(img1, img2, pos, pos, algorithm)
diffMap[pixelPos] = Math.ceil(Math.abs(delta) * 100 / maxDelta)
identical = false
}
return { identical, diffMap }
}
/**
* Gets antialias map for non-identical pixels
*
* The result is an byte array, where 3 out of 8 bits are used ( e.g. 1100001 )
* first bit just tells if it was worked on, useful when calculating partial antialias map and recalculate again
* second bit just tells if it was calculated or ignored, no antialias is calculated on identical pixels
* last bit tells if the pixel is an antialias pixel
*
* @param {object} params - function parameters
* @param {Uint8Array | Uint8ClampedArray} params.img1 - original image
* @param {Uint8Array | Uint8ClampedArray} params.img2 - image to compare
* @param {number} params.width - images width
* @param {number} params.height - images height
* @returns {Uint8Array} anti alias map
*/
export function getAntiAliasMap (params) {
validateImagePreconditions(params)
const { img1, img2, width, height } = params
const len = width * height
const antiAliasMap = new Uint8Array(len)
const a32 = new Uint32Array(img1.buffer, img1.byteOffset, len)
const b32 = new Uint32Array(img2.buffer, img2.byteOffset, len)
for (let y = 0; y < height; y++) {
for (let x = 0; x < width; x++) {
const pos = y * width + x
if (a32[pos] === b32[pos]) { // Fast way to check if pixels are identical
antiAliasMap[pos] = 0b1000_0000
} else if (antialiased(img1, x, y, width, height, img2) || antialiased(img2, x, y, width, height, img1)) {
antiAliasMap[pos] = 0b1100_0001
} else {
antiAliasMap[pos] = 0b1100_0000
}
}
}
return antiAliasMap
}
/**
* @param {object} params - function parameters
* @param {Uint8Array | Uint8ClampedArray} params.img1 - original image
* @param {Uint8Array | Uint8ClampedArray} params.img2 - image to compare
* @param {number} params.width - images width
* @param {number} params.height - images height
* @param {Uint8Array | Uint8ClampedArray | null} [params.output] - output image
* @param {Uint8Array | Uint8ClampedArray | null} [params.diffMapOutput] - output for difference map,
* useful if you need a separate image for antialias or diff
* @param {number} [params.threshold] - threshold value, integer number between 0 and 100, both
* inclusive, if the difference is below or equal the threshold, it is considered similar
* pixel, and will not count as a different pixel
* @param {boolean} [params.antialias] - whether to include anti-aliasing detection
* @param {string} [params.aaColor] - color of anti-aliased pixels in diff output
* @param {string} [params.diffColor] - color of different pixels in diff output
* @param {boolean} [params.diffMask] - whether to include anti-aliasing detection
* @param {number} [params.alpha] - // opacity of original image in diff output
* @returns {{diffPixelAmount: number, aaPixelAmount: number}} number of different pixels
*/
export function calculateDiff ({
img1, img2, output, diffMapOutput, width, height,
threshold = 10,
antialias = false,
aaColor = fallbackAAColor,
diffColor = fallbackDiffColor,
diffMask = false,
alpha = 0.1,
}) {
validateImagePreconditions({ img1, img2, width, height, output })
if (diffMapOutput && diffMapOutput.length !== width * height) { throw new Error('diffMapOutput data size does not match width/height.') }
if (img1.length !== img2.length || (output && output.length !== img1.length)) { throw new Error('Image sizes do not match.') }
const { identical, diffMap } = getNormalizedDiffs({ img1, img2, width, height, algorithm: 'CIEDE2000' })
if (identical) { // fast path if identical
if (output && !diffMask) {
for (let i = 0, len = width * height; i < len; i++) drawGrayPixel(img1, 4 * i, alpha, output)
}
return {
diffPixelAmount: 0,
aaPixelAmount: 0,
}
}
const antiAliasMap = antialias ? getAntiAliasMap({ img1, img2, width, height }) : null
const [aaR, aaG, aaB] = colorOrFallbackColorToRGBA(aaColor, fallbackAAColor)
const [diffR, diffG, diffB] = colorOrFallbackColorToRGBA(diffColor, fallbackDiffColor)
let diffPixelAmount = 0
let aaPixelAmount = 0
// compare each pixel of one image against the other one
for (let y = 0; y < height; y++) {
for (let x = 0; x < width; x++) {
const pos = (y * width + x) * 4
const normalizedDelta = diffMap[y * width + x]
// the color difference is above the threshold
if (normalizedDelta > threshold) {
// check it's a real rendering difference or just anti-aliasing
if (antiAliasMap && (antiAliasMap[y * width + x] & 1) === 1) {
// one of the pixels is anti-aliasing; draw as yellow and do not count as difference
if (output) { drawPixel(output, pos, aaR, aaG, aaB) }
if (diffMapOutput) { diffMapOutput[y * width + x] = 0b0011 }
aaPixelAmount++
} else {
// found substantial difference not caused by anti-aliasing; draw it as such
if (output) { drawPixel(output, pos, diffR, diffG, diffB) }
if (diffMapOutput) { diffMapOutput[y * width + x] = 0b0001 }
diffPixelAmount++
}
} else {
if (output && !diffMask) {
// pixels are similar; draw background as grayscale image blended with white
drawGrayPixel(img1, pos, alpha, output)
}
if (diffMapOutput) { diffMapOutput[y * width + x] = 0 }
}
}
}
// return the number of different pixels
return {
diffPixelAmount,
aaPixelAmount,
}
}
/**
* Checks if `arr` is an 8-bit unsigned integer typed array
* @param {ArrayBufferView} arr - target object
*/
function isPixelData (arr) {
return arr instanceof Uint8Array || arr instanceof Uint8ClampedArray
}
/**
* check if a pixel is likely a part of anti-aliasing;
* based on "Anti-aliased Pixel and Intensity Slope Detector" paper by V. Vysniauskas, 2009
* @param {Uint8Array | Uint8ClampedArray} img - original image
* @param {number} x1 - pixel horizontal position
* @param {number} y1 - pixel vertical position
* @param {number} width - images width
* @param {number} height - images height
* @param {Uint8Array | Uint8ClampedArray} img2 - image to compare
*/
function antialiased (img, x1, y1, width, height, img2) {
const x0 = Math.max(x1 - 1, 0)
const y0 = Math.max(y1 - 1, 0)
const x2 = Math.min(x1 + 1, width - 1)
const y2 = Math.min(y1 + 1, height - 1)
const pos = (y1 * width + x1) * 4
let zeroes = x1 === x0 || x1 === x2 || y1 === y0 || y1 === y2 ? 1 : 0
let min = 0
let max = 0
let minX = width
let minY = height
let maxX = 0
let maxY = 0
// go through 8 adjacent pixels
for (let x = x0; x <= x2; x++) {
for (let y = y0; y <= y2; y++) {
if (x === x1 && y === y1) continue
// brightness delta between the center pixel and adjacent one
const { delta } = colorDeltaImgPosition(img, img, pos, (y * width + x) * 4, 'Brightness')
// count the number of equal, darker and brighter adjacent pixels
if (delta === 0) {
zeroes++
// if found more than 2 equal siblings, it's definitely not anti-aliasing
if (zeroes > 2) return false
// remember the darkest pixel
} else if (delta < min) {
min = delta
minX = x
minY = y
// remember the brightest pixel
} else if (delta > max) {
max = delta
maxX = x
maxY = y
}
}
}
// if there are no both darker and brighter pixels among siblings, it's not anti-aliasing
if (min === 0 || max === 0) return false
// if either the darkest or the brightest pixel has 3+ equal siblings in both images
// (definitely not anti-aliased), this pixel is anti-aliased
return (hasManySiblings(img, minX, minY, width, height) && hasManySiblings(img2, minX, minY, width, height)) ||
(hasManySiblings(img, maxX, maxY, width, height) && hasManySiblings(img2, maxX, maxY, width, height))
}
// check if a pixel has 3+ adjacent pixels of the same color.
/**
*
* @param {Uint8Array | Uint8ClampedArray} img - original image
* @param {number} x1 - pixel horizontal position
* @param {number} y1 - pixel vertical position
* @param {number} width - images width
* @param {number} height - images height
*/
function hasManySiblings (img, x1, y1, width, height) {
const x0 = Math.max(x1 - 1, 0)
const y0 = Math.max(y1 - 1, 0)
const x2 = Math.min(x1 + 1, width - 1)
const y2 = Math.min(y1 + 1, height - 1)
const pos = (y1 * width + x1) * 4
let zeroes = x1 === x0 || x1 === x2 || y1 === y0 || y1 === y2 ? 1 : 0
// go through 8 adjacent pixels
for (let x = x0; x <= x2; x++) {
for (let y = y0; y <= y2; y++) {
if (x === x1 && y === y1) continue
const pos2 = (y * width + x) * 4
if (img[pos] === img[pos2] &&
img[pos + 1] === img[pos2 + 1] &&
img[pos + 2] === img[pos2 + 2] &&
img[pos + 3] === img[pos2 + 3]) zeroes++
if (zeroes > 2) return true
}
}
return false
}
/**
*
* @param {Uint8Array | Uint8ClampedArray } output - output image
* @param {number} pos - image position
* @param {number} r - rgb red value
* @param {number} g - rgb green value
* @param {number} b - rgb blue value
*/
function drawPixel (output, pos, r, g, b) {
output[pos + 0] = r
output[pos + 1] = g
output[pos + 2] = b
output[pos + 3] = 255
}
/**
*
* @param {Uint8Array | Uint8ClampedArray} img - original image
* @param {number} pos - image position
* @param {number} alpha - alpha value
* @param {Uint8Array | Uint8ClampedArray } output - output image
*/
function drawGrayPixel (img, pos, alpha, output) {
const r = img[pos + 0]
const g = img[pos + 1]
const b = img[pos + 2]
const a = alpha * img[pos + 3] / 255
const brightness = rgb2y(r, g, b)
const val = 255 + (brightness - 255) * a
drawPixel(output, pos, val, val, val)
}
/**
* @param {object} params - function parameters
* @param {Uint8Array | Uint8ClampedArray} params.img1 - original image
* @param {Uint8Array | Uint8ClampedArray} params.img2 - image to compare
* @param {Uint8Array | Uint8ClampedArray | null} [params.output] - output image
* @param {number} params.width - images width
* @param {number} params.height - images height
*/
function validateImagePreconditions ({ img1, img2, width, height, output }) {
if (!isPixelData(img1) || !isPixelData(img2) || (output && !isPixelData(output))) { throw new Error('Image data: Uint8Array or Uint8ClampedArray expected.') }
if (img1.length !== img2.length) { throw new Error('Image sizes do not match.') }
if (img1.length !== width * height * 4) { throw new Error('Image data size does not match width/height.') }
}
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