diff --git a/Conversions/RgbHsvConversion.java b/Conversions/RgbHsvConversion.java new file mode 100644 index 000000000000..60fffe7a5f72 --- /dev/null +++ b/Conversions/RgbHsvConversion.java @@ -0,0 +1,165 @@ +package Conversions; + +import java.util.Arrays; + +/** + * 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 class provides methods 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). + */ +public class RgbHsvConversion { + + public static void main(String[] args) { + // Expected RGB-values taken from https://www.rapidtables.com/convert/color/hsv-to-rgb.html + + // Test hsvToRgb-method + assert Arrays.equals(hsvToRgb(0, 0, 0), new int[] {0, 0, 0}); + assert Arrays.equals(hsvToRgb(0, 0, 1), new int[] {255, 255, 255}); + assert Arrays.equals(hsvToRgb(0, 1, 1), new int[] {255, 0, 0}); + assert Arrays.equals(hsvToRgb(60, 1, 1), new int[] {255, 255, 0}); + assert Arrays.equals(hsvToRgb(120, 1, 1), new int[] {0, 255, 0}); + assert Arrays.equals(hsvToRgb(240, 1, 1), new int[] {0, 0, 255}); + assert Arrays.equals(hsvToRgb(300, 1, 1), new int[] {255, 0, 255}); + assert Arrays.equals(hsvToRgb(180, 0.5, 0.5), new int[] {64, 128, 128}); + assert Arrays.equals(hsvToRgb(234, 0.14, 0.88), new int[] {193, 196, 224}); + assert Arrays.equals(hsvToRgb(330, 0.75, 0.5), new int[] {128, 32, 80}); + + // Test rgbToHsv-method + // approximate-assertions needed because of small deviations due to converting between + // int-values and double-values. + assert approximatelyEqualHsv(rgbToHsv(0, 0, 0), new double[] {0, 0, 0}); + assert approximatelyEqualHsv(rgbToHsv(255, 255, 255), new double[] {0, 0, 1}); + assert approximatelyEqualHsv(rgbToHsv(255, 0, 0), new double[] {0, 1, 1}); + assert approximatelyEqualHsv(rgbToHsv(255, 255, 0), new double[] {60, 1, 1}); + assert approximatelyEqualHsv(rgbToHsv(0, 255, 0), new double[] {120, 1, 1}); + assert approximatelyEqualHsv(rgbToHsv(0, 0, 255), new double[] {240, 1, 1}); + assert approximatelyEqualHsv(rgbToHsv(255, 0, 255), new double[] {300, 1, 1}); + assert approximatelyEqualHsv(rgbToHsv(64, 128, 128), new double[] {180, 0.5, 0.5}); + assert approximatelyEqualHsv(rgbToHsv(193, 196, 224), new double[] {234, 0.14, 0.88}); + assert approximatelyEqualHsv(rgbToHsv(128, 32, 80), new double[] {330, 0.75, 0.5}); + } + + /** + * 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. + */ + public static int[] hsvToRgb(double hue, double saturation, double value) { + if (hue < 0 || hue > 360) { + throw new IllegalArgumentException("hue should be between 0 and 360"); + } + + if (saturation < 0 || saturation > 1) { + throw new IllegalArgumentException("saturation should be between 0 and 1"); + } + + if (value < 0 || value > 1) { + throw new IllegalArgumentException("value should be between 0 and 1"); + } + + double chroma = value * saturation; + double hueSection = hue / 60; + double secondLargestComponent = chroma * (1 - Math.abs(hueSection % 2 - 1)); + double 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. + */ + public static double[] rgbToHsv(int red, int green, int blue) { + if (red < 0 || red > 255) { + throw new IllegalArgumentException("red should be between 0 and 255"); + } + + if (green < 0 || green > 255) { + throw new IllegalArgumentException("green should be between 0 and 255"); + } + + if (blue < 0 || blue > 255) { + throw new IllegalArgumentException("blue should be between 0 and 255"); + } + + double dRed = (double) red / 255; + double dGreen = (double) green / 255; + double dBlue = (double) blue / 255; + double value = Math.max(Math.max(dRed, dGreen), dBlue); + double chroma = value - Math.min(Math.min(dRed, dGreen), dBlue); + double saturation = value == 0 ? 0 : chroma / value; + double 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 new double[] {hue, saturation, value}; + } + + private static boolean approximatelyEqualHsv(double[] hsv1, double[] hsv2) { + boolean bHue = Math.abs(hsv1[0] - hsv2[0]) < 0.2; + boolean bSaturation = Math.abs(hsv1[1] - hsv2[1]) < 0.002; + boolean bValue = Math.abs(hsv1[2] - hsv2[2]) < 0.002; + + return bHue && bSaturation && bValue; + } + + private static int[] getRgbBySection( + double hueSection, double chroma, double matchValue, double secondLargestComponent) { + int red; + int green; + int 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 new int[] {red, green, blue}; + } + + private static int convertToInt(double input) { + return (int) Math.round(255 * input); + } +}