feat: add RGB to HSL color format conversion algorithm

Conversions/RgbHslConversion.js

@@ -0,0 +1,85 @@
+/**
+ * Given a color in RGB format, convert it to HSL format.
+ *
+ * For more info: https://www.niwa.nu/2013/05/math-behind-colorspace-conversions-rgb-hsl/
+ *
+ * @param {number[]} colorRgb - One dimensional array of integers (RGB color format).
+ * @returns {number[]} - One dimensional array of integers (HSL color format).
+ *
+ * @example
+ * const colorRgb = [24, 98, 118]
+ *
+ * const result = rgbToHsl(colorRgb)
+ *
+ * // The function returns the corresponding color in HSL format:
+ * // result = [193, 66, 28]
+ */
+
+const checkRgbFormat = (colorRgb) => colorRgb.every(c => c >= 0 && c <= 255);
+
+const rgbToHsl = (colorRgb) => {
+ if (!checkRgbFormat(colorRgb)) {
+ throw new Error('Input is not a valid RGB color.');
+ } 
+
+ let colorHsl = colorRgb
+
+ let red = Math.round(colorRgb[0])
+ let green = Math.round(colorRgb[1])
+ let blue = Math.round(colorRgb[2])
+
+ const limit = 255
+
+ colorHsl[0] = red / limit
+ colorHsl[1] = green / limit
+ colorHsl[2] = blue / limit
+
+ let minValue = Math.min(...colorHsl)
+ let maxValue = Math.max(...colorHsl)
+
+ let channel = 0
+
+ if (maxValue === colorHsl[1]) {
+ channel = 1
+ } else if (maxValue === colorHsl[2]) {
+ channel = 2
+ }
+
+ let luminance = (minValue + maxValue) / 2
+
+ let saturation = 0
+
+ if (minValue !== maxValue) {
+ if (luminance <= 0.5) {
+ saturation = (maxValue - minValue) / (maxValue + minValue)
+ } else {
+ saturation = (maxValue - minValue) / (2 - maxValue - minValue)
+ }
+ }
+
+ let hue = 0
+
+ if (saturation !== 0) {
+ if (channel === 0) {
+ hue = (colorHsl[1] - colorHsl[2]) / (maxValue - minValue)
+ } else if (channel === 1) {
+ hue = 2 + (colorHsl[2] - colorHsl[0]) / (maxValue - minValue)
+ } else {
+ hue = 4 + (colorHsl[0] - colorHsl[1]) / (maxValue - minValue)
+ }
+ }
+
+ hue *= 60
+
+ if (hue < 0) {
+ hue += 360
+ }
+
+ colorHsl[0] = Math.round(hue)
+ colorHsl[1] = Math.round(saturation * 100)
+ colorHsl[2] = Math.round(luminance * 100)
+
+ return colorHsl
+}
+
+export { rgbToHsl }

Conversions/test/RgbHslConversion.test.js

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+import { rgbToHsl } from '../RgbHslConversion'
+describe('RgbHslConversion', () => {
+ const validTestCases = [
+ [
+ [215, 19, 180],
+ [311, 84, 46]
+ ],
+ [
+ [21, 190, 18],
+ [119, 83, 41]
+ ],
+ [
+ [80, 100, 160],
+ [225, 33, 47]
+ ],
+ [
+ [80, 1, 16],
+ [349, 98, 16]
+ ],
+ [
+ [8, 20, 0],
+ [96, 100, 4]
+ ],
+ [
+ [0, 0, 0],
+ [0, 0, 0]
+ ],
+ [
+ [255, 255, 255],
+ [0, 0, 100]
+ ]
+ ]
+
+ const errorTestCases = [
+ [[256, 180, 9], 'Input is not a valid RGB color.'],
+ [[-90, 46, 8], 'Input is not a valid RGB color.'],
+ [[1, 39, 900], 'Input is not a valid RGB color.']
+ ]
+
+
+ test.each(validTestCases)(
+ 'Should return the color in HSL format.',
+ (colorRgb, expected) => {
+ expect(rgbToHsl(colorRgb)).toEqual(expected)
+ }
+ )
+
+ test.each(errorTestCases)(
+ 'Should return the error message.',
+ (colorRgb, expected) => {
+ expect(() => rgbToHsl(colorRgb)).toThrowError(expected)
+ }
+ )
+})