feat: add RGB to HSL color format conversion algorithm (#1475)

* feat: add RGB to HSL color format conversion algorithm

* test: add self-tests for rgb to hsl conversion algorithm

* fix: change function code to concise format

* fix: use throw and segregate the test cases

* chore: clean up the test format

* chore: use correct styling

Author: piyushk77

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

@@ -0,0 +1,43 @@
+import { rgbToHsl } from '../RgbHslConversion'
+describe('RgbHslConversion', () => {
+  test.each([
+    [
+      [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]
+    ]
+  ])('Should return the color in HSL format.', (colorRgb, expected) => {
+    expect(rgbToHsl(colorRgb)).toEqual(expected)
+  })
+
+  test.each([
+    [[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.']
+  ])('Should return the error message.', (colorRgb, expected) => {
+    expect(() => rgbToHsl(colorRgb)).toThrowError(expected)
+  })
+})