Change project structure to a Maven Java project + Refactor (#2816)

src/main/java/com/thealgorithms/conversions/RgbHsvConversion.java

@@ -0,0 +1,167 @@
+package com.thealgorithms.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);
+    }
+}