#### Color Contrast Ratio

d
```package com.thealgorithms.misc;

import java.awt.Color;

/**
* @brief A Java implementation of the official W3 documented procedure to
* calculate contrast ratio between colors on the web. This is used to calculate
* the readability of a foreground color on top of a background color.
* @since 2020-10-15
* @see [Color Contrast
* Ratio](https://www.w3.org/TR/WCAG20-TECHS/G17.html#G17-procedure)
* @author [Seth Falco](https://github.com/SethFalco)
*/
public class ColorContrastRatio {

/**
* @brief Calculates the contrast ratio between two given colors.
* @param a Any color, used to get the red, green, and blue values.
* @param b Another color, which will be compared against the first color.
* @return The contrast ratio between the two colors.
*/
public double getContrastRatio(Color a, Color b) {
final double aColorLuminance = getRelativeLuminance(a);
final double bColorLuminance = getRelativeLuminance(b);

if (aColorLuminance > bColorLuminance) {
return (aColorLuminance + 0.05) / (bColorLuminance + 0.05);
}

return (bColorLuminance + 0.05) / (aColorLuminance + 0.05);
}

/**
* @brief Calculates the relative luminance of a given color.
* @param color Any color, used to get the red, green, and blue values.
* @return The relative luminance of the color.
* luminance.](https://www.w3.org/TR/2008/REC-WCAG20-20081211/#relativeluminancedef)
*/
public double getRelativeLuminance(Color color) {
final double red = getColor(color.getRed());
final double green = getColor(color.getGreen());
final double blue = getColor(color.getBlue());

return 0.2126 * red + 0.7152 * green + 0.0722 * blue;
}

/**
* @brief Calculates the final value for a color to be used in the relative
* luminance formula as described in step 1.
* @param color8Bit 8-bit representation of a color component value.
* @return Value for the provided color component to be used in the relative
* luminance formula.
*/
public double getColor(int color8Bit) {
final double sRgb = getColorSRgb(color8Bit);
return (sRgb <= 0.03928) ? sRgb / 12.92 : Math.pow((sRgb + 0.055) / 1.055, 2.4);
}

/**
* @brief Calculates the Color sRGB value as denoted in step 1 of the
* procedure document.
* @param color8Bit 8-bit representation of a color component value.
* @return A percentile value of the color component.
*/
private double getColorSRgb(double color8Bit) {
return color8Bit / 255.0;
}

/**
* You can check this example against another open-source implementation
* available on GitHub.
*
* @see [Online Contrast
* Ratio](https://contrast-ratio.com/#rgb%28226%2C%20229%2C%20248-on-rgb%2823%2C%20103%2C%20154%29)
* @see [GitHub Repository for Online Contrast
* Ratio](https://github.com/LeaVerou/contrast-ratio)
*/
private static void test() {
final ColorContrastRatio algImpl = new ColorContrastRatio();

final Color black = Color.BLACK;
final double blackLuminance = algImpl.getRelativeLuminance(black);
assert blackLuminance == 0 : "Test 1 Failed - Incorrect relative luminance.";

final Color white = Color.WHITE;
final double whiteLuminance = algImpl.getRelativeLuminance(white);
assert whiteLuminance == 1 : "Test 2 Failed - Incorrect relative luminance.";

final double highestColorRatio = algImpl.getContrastRatio(black, white);
assert highestColorRatio == 21 : "Test 3 Failed - Incorrect contrast ratio.";

final Color foreground = new Color(23, 103, 154);
final double foregroundLuminance = algImpl.getRelativeLuminance(foreground);
assert foregroundLuminance == 0.12215748057375966 : "Test 4 Failed - Incorrect relative luminance.";

final Color background = new Color(226, 229, 248);
final double backgroundLuminance = algImpl.getRelativeLuminance(background);
assert backgroundLuminance == 0.7898468477881603 : "Test 5 Failed - Incorrect relative luminance.";

final double contrastRatio = algImpl.getContrastRatio(foreground, background);
assert contrastRatio == 4.878363954846178 : "Test 6 Failed - Incorrect contrast ratio.";
}

public static void main(String[] args) {
test();
}
}
```