feat: add HSL to RGB color space conversion algorithm

Conversions/HslToRgbConversion.js

@@ -0,0 +1,85 @@
+/**
+ * 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 }

Conversions/test/HslToRgbConversion.test.js

@@ -0,0 +1,44 @@
+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)
+  })
+})