Tests whether the given colors are contrasting colors, according to the test described in the W3C accessibility evaluation working draft - Java 2D Graphics

Java examples for 2D Graphics:Color

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Description

Tests whether the given colors are contrasting colors, according to the test described in the W3C accessibility evaluation working draft

Demo Code

/*/*  w  w  w.j  av a2 s  .  c  o m*/
 * Copyright 2010 Google Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
//package com.java2s;
import java.awt.Color;

public class Main {
    /**
     * Tests whether the given colors are contrasting colors, according to the
     * test described in the W3C accessibility evaluation working draft
     * {@link "http://www.w3.org/TR/AERT#color-contrast"}.  This is a lenient
     * version of the test which allows the user to pass in the accepted leniency
     * margin.
     *
     * <p>The value of the leniency margin is in the range 0 to 1.0.  0 means
     * that the test is not lenient at all, 1.0 means that the test will pass for
     * all colors that are different.  It is recommended not to use values of more
     * than 0.01.
     *
     * @param color1 the first of the two checked colors
     * @param color2 the second of the two checked colors
     * @param margin the test leniency margin
     * @return whether the given colors are considered contrasting, taking the
     *     leniency margin into account
     */
    public static boolean testContrast(Color color1, Color color2,
            float margin) {
        float differenceFraction = 1f - margin;
        return luminanceDiff(color1, color2) > 125 * differenceFraction
                && colorDiff(color1, color2) > 500 * differenceFraction;
    }

    /**
     * Tests whether the given colors are contrasting colors, according to the
     * test described in the W3C accessibility evaluation working draft
     * {@link "http://www.w3.org/TR/AERT#color-contrast"}.
     *
     * @param color1 the first of the two checked colors
     * @param color2 the second of the two checked colors
     * @return whether the given colors are considered contrasting
     */
    public static boolean testContrast(Color color1, Color color2) {
        return luminanceDiff(color1, color2) > 125
                && colorDiff(color1, color2) > 500;
    }

    /**
     * Computes the luminance difference of two colors (a value in range 0-255).
     * It is the luminance value equal to the Y component of the YIQ or the YUV
     * color space models.
     */
    public static int luminanceDiff(Color c1, Color c2) {
        return Math.abs(luminance(c1) - luminance(c2));
    }

    /**
     * Calculates the Manhattan distance of two colors in the RGB color space
     * (a value in range 0-(255*3)).
     */
    public static int colorDiff(Color color1, Color color2) {
        return colorDiff(color1.getRed(), color1.getGreen(),
                color1.getBlue(), color2.getRed(), color2.getGreen(),
                color2.getBlue());
    }

    /**
     * Calculates the Manhattan distance of two colors in the RGB color space
     * (a value in range 0-(255*3)).
     */
    public static int colorDiff(int r1, int g1, int b1, int r2, int g2,
            int b2) {
        return Math.abs(r1 - r2) + Math.abs(g1 - g2) + Math.abs(b1 - b2);
    }

    /**
     * Computes the luminance value of a color (a value in range 0-255).
     * It is the luminance value equal to the Y component of the YIQ or the YUV
     * color space models.
     */
    public static int luminance(Color color) {
        return luminance(color.getRed(), color.getGreen(), color.getBlue());
    }

    /**
     * Computes the luminance value of a color (a value in range 0-255).
     * It is the luminance value equal to the Y component of the YIQ or the YUV
     * color space models.
     */
    public static int luminance(int red, int green, int blue) {
        return (red * 299 + green * 587 + blue * 114) / 1000;
    }
}

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