b4d104db23
* Added algorithm for color contrast ratio.
* Added comment and example usage in main.
* Fixed calling method in main without creating object.
* Formatted with Google Java Formatter
* Add imports for ColorContrastRatio.java
* updating DIRECTORY.md
* Updated to follow repo conventions. Undid formatting of documents.
* Follow repository conventions.
* Formatted with Google Java Formatter
* Added test method with assetions.
* Formatted with Google Java Formatter
* Update Misc/ColorContrastRatio.java
Co-authored-by: Ayaan Khan <ayaankhan98@gmail.com>
* updating DIRECTORY.md
* Correct javadocs and parameter names.
* Formatted with Google Java Formatter
Co-authored-by: github-actions <${GITHUB_ACTOR}@users.noreply.github.com>
Co-authored-by: Ayaan Khan <ayaankhan98@gmail.com>
105 lines
4.1 KiB
Java
105 lines
4.1 KiB
Java
package Misc;
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import java.awt.Color;
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/**
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* @brief A Java implementation of the offcial W3 documented procedure to calculate contrast ratio
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* between colors on the web. This is used to calculate the readability of a foreground color on
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* top of a background color.
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* @since 2020-10-15
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* @see [Color Contrast Ratio](https://www.w3.org/TR/WCAG20-TECHS/G17.html#G17-procedure)
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* @author [Seth Falco](https://github.com/SethFalco)
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*/
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public class ColorContrastRatio {
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/**
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* @brief Calculates the contrast ratio between two given colors.
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* @param a Any color, used to get the red, green, and blue values.
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* @param b Another color, which will be compared against the first color.
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* @return The contrast ratio between the two colors.
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*/
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public double getContrastRatio(Color a, Color b) {
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final double aColorLuminance = getRelativeLuminance(a);
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final double bColorLuminance = getRelativeLuminance(b);
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if (aColorLuminance > bColorLuminance)
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return (aColorLuminance + 0.05) / (bColorLuminance + 0.05);
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return (bColorLuminance + 0.05) / (aColorLuminance + 0.05);
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}
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/**
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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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*/
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public double getRelativeLuminance(Color color) {
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final double red = getColor(color.getRed());
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final double green = getColor(color.getGreen());
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final double blue = getColor(color.getBlue());
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return 0.2126 * red + 0.7152 * green + 0.0722 * blue;
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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 luminance formula as
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* 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 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 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 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 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
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: "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
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: "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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}
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