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import { distYIQ, distCIEDE2000, distRGB, distRieRGB, distYIQBrightness } from './color-metrics.js'
/** @param {number} num - number to round */
const rounded = (num) => +num.toFixed(5)
export const maxDelta = {
YIQ: rounded(distYIQ(0, 0, 0, 255, 255, 255)),
RGB: rounded(distRGB(0, 0, 0, 255, 255, 255)),
RieRGB: rounded(distRieRGB(0, 0, 0, 255, 255, 255)),
CIEDE2000: rounded(distCIEDE2000(0, 0, 0, 255, 255, 255)),
Brightness: rounded(Math.abs(distYIQBrightness(0, 0, 0, 255, 255, 255))),
}
export const validAlgorithms = Object.freeze(/** @type {const} */(['YIQ', 'CIEDE2000', 'RGB', 'RieRGB', 'Brightness']))
/** @typedef {(typeof validAlgorithms)[number]} Algorithm */
/**
*
* @param {Uint8Array | Uint8ClampedArray} img1 - original image
* @param {Uint8Array | Uint8ClampedArray} img2 - image to compare
* @param {number} posImg1 - pixel position on `img1`
* @param {number} posImg2 - pixel position on `img2`
* @param {Algorithm} algorithm - algorithm used to calculate delta defaults to CIEDE2000
* @returns {colorDelta} color delta result
*/
export function colorDeltaImgPosition (img1, img2, posImg1, posImg2, algorithm) {
const r1 = img1[posImg1 + 0]
const g1 = img1[posImg1 + 1]
const b1 = img1[posImg1 + 2]
const a1 = img1[posImg1 + 3]
const r2 = img2[posImg2 + 0]
const g2 = img2[posImg2 + 1]
const b2 = img2[posImg2 + 2]
const a2 = img2[posImg2 + 3]
return colorDelta(r1, g1, b1, a1, r2, g2, b2, a2, algorithm)
}
/**
* calculate color difference according to the paper "Measuring perceived color difference
* using YIQ NTSC transmission color space in mobile applications" by Y. Kotsarenko and F. Ramos
* @param {number} r1 - color 1 rgba red value
* @param {number} g1 - color 1 rgba green value
* @param {number} b1 - color 1 rgba blue value
* @param {number} a1 - color 1 rgba alpha value
* @param {number} r2 - color 2 rgba red value
* @param {number} g2 - color 2 rgba green value
* @param {number} b2 - color 2 rgba blue value
* @param {number} a2 - color 2 rgba alpha value
* @param {Algorithm} algorithm - algorithm used to calculate delta defaults to CIEDE2000
* @returns {colorDelta} color delta result
*/
export function colorDelta (r1, g1, b1, a1, r2, g2, b2, a2, algorithm) {
algorithm = Object.hasOwn(maxDelta, algorithm) ? algorithm : 'CIEDE2000'
if (a1 === a2 && r1 === r2 && g1 === g2 && b1 === b2) {
return {
delta: 0,
maxDelta: maxDelta[algorithm],
}
}
const algorithmFunction = (() => {
switch (algorithm) {
case 'YIQ': return distYIQ
case 'RGB': return distRGB
case 'RieRGB': return distRieRGB
case 'Brightness': return distYIQBrightness
case 'CIEDE2000':
default: return distCIEDE2000
}
})()
if (a1 < 255 || a2 < 255) {
const rgb1Light = colorBlend(r1, g1, b1, a1, 255, 255, 255)
const rgb2Light = colorBlend(r2, g2, b2, a2, 255, 255, 255)
const deltaLightBlend = rounded(algorithmFunction(
rgb1Light.R, rgb1Light.G, rgb1Light.B,
rgb2Light.R, rgb2Light.G, rgb2Light.B
))
const rgb1Dark = colorBlend(r1, g1, b1, a1, 0, 0, 0)
const rgb2Dark = colorBlend(r2, g2, b2, a2, 0, 0, 0)
const deltaDarkBlend = rounded(algorithmFunction(
rgb1Dark.R, rgb1Dark.G, rgb1Dark.B,
rgb2Dark.R, rgb2Dark.G, rgb2Dark.B
))
return {
delta: Math.max(deltaLightBlend, deltaDarkBlend),
maxDelta: maxDelta[algorithm],
}
}
const delta = rounded(algorithmFunction(r1, g1, b1, r2, g2, b2))
return {
delta,
maxDelta: maxDelta[algorithm],
}
}
/**
* @typedef {object} colorDelta
* @property {number} delta - color delta result
* @property {number} maxDelta - max possible result value
*/
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