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refactor: ColorContrastRatio (#5457)
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Lines changed: 38 additions & 49 deletions

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‎src/main/java/com/thealgorithms/misc/ColorContrastRatio.java‎

Lines changed: 5 additions & 49 deletions
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@@ -7,8 +7,7 @@
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* calculate contrast ratio between colors on the web. This is used to calculate
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* the readability of a foreground color on top of a background color.
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* @since 2020-10-15
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* @see [Color Contrast
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* Ratio](https://www.w3.org/TR/WCAG20-TECHS/G17.html#G17-procedure)
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* @see <a href="https://www.w3.org/TR/WCAG20-TECHS/G17.html#G17-procedure">Color Contrast Ratio</a>
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* @author [Seth Falco](https://github.com/SethFalco)
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*/
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public class ColorContrastRatio {
@@ -34,8 +33,7 @@ public double getContrastRatio(Color a, Color b) {
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* @brief Calculates the relative luminance of a given color.
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* @param color Any color, used to get the red, green, and blue values.
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* @return The relative luminance of the color.
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* @see [More info on relative
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* luminance.](https://www.w3.org/TR/2008/REC-WCAG20-20081211/#relativeluminancedef)
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* @see <a href="https://www.w3.org/TR/2008/REC-WCAG20-20081211/#relativeluminancedef">More info on relative luminance.</a>
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*/
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public double getRelativeLuminance(Color color) {
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final double red = getColor(color.getRed());
@@ -46,63 +44,21 @@ public double getRelativeLuminance(Color color) {
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}
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/**
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* @brief Calculates the final value for a color to be used in the relative
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* luminance formula as described in step 1.
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* @brief Calculates the final value for a color to be used in the relative luminance formula as described in step 1.
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* @param color8Bit 8-bit representation of a color component value.
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* @return Value for the provided color component to be used in the relative
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* luminance formula.
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* @return Value for the provided color component to be used in the relative luminance formula.
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*/
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public double getColor(int color8Bit) {
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final double sRgb = getColorSRgb(color8Bit);
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return (sRgb <= 0.03928) ? sRgb / 12.92 : Math.pow((sRgb + 0.055) / 1.055, 2.4);
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}
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/**
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* @brief Calculates the Color sRGB value as denoted in step 1 of the
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* procedure document.
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* @brief Calculates the Color sRGB value as denoted in step 1 of the procedure document.
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* @param color8Bit 8-bit representation of a color component value.
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* @return A percentile value of the color component.
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*/
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private double getColorSRgb(double color8Bit) {
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return color8Bit / 255.0;
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}
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/**
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* You can check this example against another open-source implementation
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* available on GitHub.
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*
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* @see [Online Contrast
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* Ratio](https://contrast-ratio.com/#rgb%28226%2C%20229%2C%20248-on-rgb%2823%2C%20103%2C%20154%29)
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* @see [GitHub Repository for Online Contrast
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* Ratio](https://github.com/LeaVerou/contrast-ratio)
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*/
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private static void test() {
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final ColorContrastRatio algImpl = new ColorContrastRatio();
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final Color black = Color.BLACK;
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final double blackLuminance = algImpl.getRelativeLuminance(black);
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assert blackLuminance == 0 : "Test 1 Failed - Incorrect relative luminance.";
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final Color white = Color.WHITE;
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final double whiteLuminance = algImpl.getRelativeLuminance(white);
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assert whiteLuminance == 1 : "Test 2 Failed - Incorrect relative luminance.";
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final double highestColorRatio = algImpl.getContrastRatio(black, white);
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assert highestColorRatio == 21 : "Test 3 Failed - Incorrect contrast ratio.";
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final Color foreground = new Color(23, 103, 154);
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final double foregroundLuminance = algImpl.getRelativeLuminance(foreground);
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assert foregroundLuminance == 0.12215748057375966 : "Test 4 Failed - Incorrect relative luminance.";
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final Color background = new Color(226, 229, 248);
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final double backgroundLuminance = algImpl.getRelativeLuminance(background);
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assert backgroundLuminance == 0.7898468477881603 : "Test 5 Failed - Incorrect relative luminance.";
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final double contrastRatio = algImpl.getContrastRatio(foreground, background);
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assert contrastRatio == 4.878363954846178 : "Test 6 Failed - Incorrect contrast ratio.";
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}
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public static void main(String[] args) {
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test();
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}
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}

‎src/test/java/com/thealgorithms/misc/ColorContrastRatioTest.java‎

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package com.thealgorithms.misc;
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import static org.junit.jupiter.api.Assertions.assertEquals;
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import java.awt.Color;
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import java.util.stream.Stream;
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import org.junit.jupiter.params.ParameterizedTest;
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import org.junit.jupiter.params.provider.Arguments;
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import org.junit.jupiter.params.provider.MethodSource;
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class ColorContrastRatioTest {
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private final ColorContrastRatio colorContrastRationCalculator = new ColorContrastRatio();
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static Stream<Arguments> relativeLuminanceProvider() {
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return Stream.of(Arguments.of(Color.BLACK, 0.0), Arguments.of(Color.WHITE, 1.0), Arguments.of(new Color(23, 103, 154), 0.12215748057375966), Arguments.of(new Color(226, 229, 248), 0.7898468477881603));
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}
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static Stream<Arguments> contrastRatioProvider() {
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return Stream.of(Arguments.of(Color.BLACK, Color.WHITE, 21.0), Arguments.of(new Color(23, 103, 154), new Color(226, 229, 248), 4.878363954846178));
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}
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@ParameterizedTest
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@MethodSource("relativeLuminanceProvider")
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void testGetRelativeLuminance(Color color, double expectedLuminance) {
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assertEquals(expectedLuminance, colorContrastRationCalculator.getRelativeLuminance(color), 1e-10);
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}
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@ParameterizedTest
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@MethodSource("contrastRatioProvider")
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void testGetContrastRatio(Color a, Color b, double expectedRatio) {
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assertEquals(expectedRatio, colorContrastRationCalculator.getContrastRatio(a, b), 1e-10);
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}
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}

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