Add RGB-HSV conversion

Conversions/RgbHsvConversion.js

@@ -0,0 +1,180 @@
+/**
+ * The RGB color model is an additive color model in which red, green, and blue light are added
+ * together in various ways to reproduce a broad array of colors. The name of the model comes from
+ * the initials of the three additive primary colors, red, green, and blue. Meanwhile, the HSV
+ * representation models how colors appear under light. In it, colors are represented using three
+ * components: hue, saturation and (brightness-)value. This file provides functions for converting
+ * colors from one representation to the other. (description adapted from
+ * https://en.wikipedia.org/wiki/RGB_color_model and https://en.wikipedia.org/wiki/HSL_and_HSV).
+ */
+
+/*
+Doctests
+Expected RGB-values taken from https://www.rapidtables.com/convert/color/hsv-to-rgb.html
+Test hsvToRgb-method
+
+> hsvToRgb(0, 0, 0)
+[0, 0, 0]
+> hsvToRgb(0, 0, 1)
+[255, 255, 255]
+> hsvToRgb(0, 1, 1)
+[255, 0, 0]
+> hsvToRgb(60, 1, 1)
+[255, 255, 0]
+> hsvToRgb(120, 1, 1)
+[0, 255, 0]
+> hsvToRgb(240, 1, 1)
+[0, 0, 255]
+> hsvToRgb(300, 1, 1)
+[255, 0, 255]
+> hsvToRgb(180, 0.5, 0.5)
+[64, 128, 128]
+> hsvToRgb(234, 0.14, 0.88)
+[193, 196, 224]
+> hsvToRgb(330, 0.75, 0.5)
+[128, 32, 80]
+
+Test rgbToHsv-method
+function "approximatelyEqualHsv" needed because of small deviations due to rounding for the RGB-values.
+> approximatelyEqualHsv(rgbToHsv(0, 0, 0), [0, 0, 0])
+true
+> approximatelyEqualHsv(rgbToHsv(255, 255, 255), [0, 0, 1])
+true
+> approximatelyEqualHsv(rgbToHsv(255, 0, 0), [0, 1, 1])
+true
+> approximatelyEqualHsv(rgbToHsv(255, 255, 0), [60, 1, 1])
+true
+> approximatelyEqualHsv(rgbToHsv(0, 255, 0), [120, 1, 1])
+true
+> approximatelyEqualHsv(rgbToHsv(0, 0, 255), [240, 1, 1])
+true
+> approximatelyEqualHsv(rgbToHsv(255, 0, 255), [300, 1, 1])
+true
+> approximatelyEqualHsv(rgbToHsv(64, 128, 128), [180, 0.5, 0.5])
+true
+> approximatelyEqualHsv(rgbToHsv(193, 196, 224), [234, 0.14, 0.88])
+true
+> approximatelyEqualHsv(rgbToHsv(128, 32, 80), [330, 0.75, 0.5])
+true
+
+*/
+
+/**
+ * Conversion from the HSV-representation to the RGB-representation.
+ *
+ * @param hue Hue of the color.
+ * @param saturation Saturation of the color.
+ * @param value Brightness-value of the color.
+ * @return The tuple of RGB-components.
+ */
+function hsvToRgb (hue, saturation, value) { // eslint-disable-line no-unused-vars
+  if (hue < 0 || hue > 360) {
+    throw new Error('hue should be between 0 and 360')
+  }
+
+  if (saturation < 0 || saturation > 1) {
+    throw new Error('saturation should be between 0 and 1')
+  }
+
+  if (value < 0 || value > 1) {
+    throw new Error('value should be between 0 and 1')
+  }
+
+  const chroma = value * saturation
+  const hueSection = hue / 60
+  const secondLargestComponent = chroma * (1 - Math.abs(hueSection % 2 - 1))
+  const matchValue = value - chroma
+
+  return getRgbBySection(hueSection, chroma, matchValue, secondLargestComponent)
+}
+
+/**
+ * Conversion from the RGB-representation to the HSV-representation.
+ *
+ * @param red Red-component of the color.
+ * @param green Green-component of the color.
+ * @param blue Blue-component of the color.
+ * @return The tuple of HSV-components.
+ */
+function rgbToHsv (red, green, blue) { // eslint-disable-line no-unused-vars
+  if (red < 0 || red > 255) {
+    throw new Error('red should be between 0 and 255')
+  }
+
+  if (green < 0 || green > 255) {
+    throw new Error('green should be between 0 and 255')
+  }
+
+  if (blue < 0 || blue > 255) {
+    throw new Error('blue should be between 0 and 255')
+  }
+
+  const dRed = red / 255
+  const dGreen = green / 255
+  const dBlue = blue / 255
+  const value = Math.max(Math.max(dRed, dGreen), dBlue)
+  const chroma = value - Math.min(Math.min(dRed, dGreen), dBlue)
+  const saturation = value === 0 ? 0 : chroma / value
+  let hue
+
+  if (chroma === 0) {
+    hue = 0
+  } else if (value === dRed) {
+    hue = 60 * (0 + (dGreen - dBlue) / chroma)
+  } else if (value === dGreen) {
+    hue = 60 * (2 + (dBlue - dRed) / chroma)
+  } else {
+    hue = 60 * (4 + (dRed - dGreen) / chroma)
+  }
+
+  hue = (hue + 360) % 360
+
+  return [hue, saturation, value]
+}
+
+function approximatelyEqualHsv (hsv1, hsv2) { // eslint-disable-line no-unused-vars
+  const bHue = Math.abs(hsv1[0] - hsv2[0]) < 0.2
+  const bSaturation = Math.abs(hsv1[1] - hsv2[1]) < 0.002
+  const bValue = Math.abs(hsv1[2] - hsv2[2]) < 0.002
+
+  return bHue && bSaturation && bValue
+}
+
+function getRgbBySection (
+  hueSection, chroma, matchValue, secondLargestComponent) {
+  function convertToInt (input) {
+    return Math.round(255 * input)
+  }
+
+  let red
+  let green
+  let blue
+
+  if (hueSection >= 0 && hueSection <= 1) {
+    red = convertToInt(chroma + matchValue)
+    green = convertToInt(secondLargestComponent + matchValue)
+    blue = convertToInt(matchValue)
+  } else if (hueSection > 1 && hueSection <= 2) {
+    red = convertToInt(secondLargestComponent + matchValue)
+    green = convertToInt(chroma + matchValue)
+    blue = convertToInt(matchValue)
+  } else if (hueSection > 2 && hueSection <= 3) {
+    red = convertToInt(matchValue)
+    green = convertToInt(chroma + matchValue)
+    blue = convertToInt(secondLargestComponent + matchValue)
+  } else if (hueSection > 3 && hueSection <= 4) {
+    red = convertToInt(matchValue)
+    green = convertToInt(secondLargestComponent + matchValue)
+    blue = convertToInt(chroma + matchValue)
+  } else if (hueSection > 4 && hueSection <= 5) {
+    red = convertToInt(secondLargestComponent + matchValue)
+    green = convertToInt(matchValue)
+    blue = convertToInt(chroma + matchValue)
+  } else {
+    red = convertToInt(chroma + matchValue)
+    green = convertToInt(matchValue)
+    blue = convertToInt(secondLargestComponent + matchValue)
+  }
+
+  return [red, green, blue]
+}