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feat: add HSL to RGB color space conversion algorithm #1518

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c9342e8
feat: add HSL to RGB conversion algorithm
piyushk77 Oct 12, 2023
c0f47f0
test: add self-tests for hsl to rgb conversion algorithm
piyushk77 Oct 12, 2023
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85 changes: 85 additions & 0 deletions Conversions/HslToRgbConversion.js
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/**
* Given a color in HSL format, convert it to RGB format.
*
* @see
* For more info: https://www.niwa.nu/2013/05/math-behind-colorspace-conversions-rgb-hsl/
*
* @param {number[]} colorHsl - One dimensional array of integers (HSL color format).
* @returns {number[]} - One dimensional array of integers (RGB color format).
*
* @example
* const colorHsl = [120, 50, 15]
*
* const result = hslToRgb(colorHsl)
*
* // The function returns the corresponding color in RGB format:
* // result = [19, 57, 19]
*/

const checkHslFormat = (colorHsl) => {
return (
colorHsl[0] >= 0 &&
colorHsl[0] <= 360 &&
colorHsl[1] >= 0 &&
colorHsl[1] <= 100 &&
colorHsl[2] >= 0 &&
colorHsl[2] <= 100
)
}

const hslToRgb = (colorHsl) => {
if (!checkHslFormat(colorHsl)) {
throw new Error('Input is not a valid HSL color.')
}

let luminance = colorHsl[2] / 100

// Check if color is a shade of grey
if (colorHsl[1] === 0) {
let colorRgb = new Array(3).fill(255 * luminance)
return colorRgb
}

let firstFormula = 0

if (luminance < 0.5) {
firstFormula = luminance * (1 + colorHsl[1] / 100)
} else {
firstFormula =
luminance + colorHsl[1] / 100 - (luminance * colorHsl[1]) / 100
}

let secondFormula = 2 * luminance - firstFormula

// Normalize Hue
let hue = colorHsl[0] / 360
let colorRgb = colorHsl
colorRgb[0] = hue + 1 / 3
colorRgb[1] = hue
colorRgb[2] = hue - 1 / 3

for (let i = 0; i <= 2; i++) {
if (colorRgb[i] < 0) {
colorRgb[i] += 1
} else if (colorRgb[i] > 1) {
colorRgb[i] -= 1
}

if (6 * colorRgb[i] < 1) {
colorRgb[i] =
secondFormula + (firstFormula - secondFormula) * 6 * colorRgb[i]
} else if (2 * colorRgb[i] < 1) {
colorRgb[i] = firstFormula
} else if (3 * colorRgb[i] < 2) {
colorRgb[i] =
secondFormula +
(firstFormula - secondFormula) * 6 * (2 / 3 - colorRgb[i])
} else {
colorRgb[i] = secondFormula
}
colorRgb[i] = Math.round(colorRgb[i] * 255)
}
return colorRgb
}

export { hslToRgb }
44 changes: 44 additions & 0 deletions Conversions/test/HslToRgbConversion.test.js
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import { hslToRgb } from '../HslToRgbConversion'
describe('HslToRgbConversion', () => {
test.each([
[
[311, 84, 46],
[216, 19, 180]
],
[
[119, 83, 41],
[21, 191, 18]
],
[
[225, 33, 47],
[80, 100, 159]
],
[
[349, 98, 16],
[81, 1, 15]
],
[
[96, 100, 4],
[8, 20, 0]
],
[
[0, 0, 0],
[0, 0, 0]
],
[
[0, 0, 100],
[255, 255, 255]
]
])('Should return the color in RGB format.', (colorHsl, expected) => {
expect(hslToRgb(colorHsl)).toEqual(expected)
})

test.each([
[[360, 180, 9], 'Input is not a valid HSL color.'],
[[-90, 46, 8], 'Input is not a valid HSL color.'],
[[1, 39, 900], 'Input is not a valid HSL color.'],
[[1, 139, 100], 'Input is not a valid HSL color.']
])('Should return the error message.', (colorHsl, expected) => {
expect(() => hslToRgb(colorHsl)).toThrowError(expected)
})
})