Composes two colors with the ARGB format - Java 2D Graphics

Java examples for 2D Graphics:Color RGB

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Description

Composes two colors with the ARGB format

Demo Code

/**//  ww  w  .j av  a2s. c o m
 * Utility class to deal with ARGB color format
 *
 * @author Aritz Lopez
 * @license Lesser GNU Public License v3 (http://www.gnu.org/licenses/lgpl.html)
 */
//package com.java2s;

public class Main {
    public static void main(String[] argv) throws Exception {
        int foreground = 2;
        int background = 2;
        System.out.println(composite(foreground, background));
    }

    /**
     * The mask to get the two least significant bytes of an integer;
     */
    public static final int MASK = 0xFF;
    /**
     * The shifting used to put the alpha component in position
     */
    public static final int ALPHA_SHIFT = 24;
    /**
     * The shifting used to put the red component in position
     */
    public static final int RED_SHIFT = 16;
    /**
     * The shifting used to put the green component in position
     */
    public static final int GREEN_SHIFT = 8;

    /**
     * Composes two colors with the ARGB format: <br />
     * The format of the color integer is as follows: 0xAARRGGBB
     * Where:
     * <ol>
     * <li>AA is the alpha component (0-255)</li>
     * <li>RR is the red component (0-255)</li>
     * <li>GG is the green component (0-255)</li>
     * <li>BB is the blue component (0-255)</li>
     * </ol>
     * NOTE: The source of this method is quite obscure, but it's done this way because it's performance-critical (this method could be run thousands of times per second!)<br />
     * The code (unobscured) does this: <br /><br />
     * <code>
     * double alpha1 = getAlpha(foreground) / 256.0;<br />
     * double alpha2 = getAlpha(background) / 256.0;<br />
     * <br />
     * if (alpha1 == 1.0 || alpha2 == 0) return foreground;<br />
     * else if (alpha1 == 0) return background;<br />
     * <br />
     * int red1 = getRed(foreground);<br />
     * int red2 = getRed(background);<br />
     * int green1 = getGreen(foreground);<br />
     * int green2 = getGreen(background);<br />
     * int blue1 = getBlue(foreground);<br />
     * int blue2 = getBlue(background);<br />
     * <br />
     * double doubleAlpha = (alpha1 + alpha2 * (1 - alpha1));<br />
     * int finalAlpha = (int) (doubleAlpha * 256);<br />
     * <br />
     * double cAlpha2 = alpha2 * (1 - alpha1) * 0.5;<br />
     * <br />
     * int finalRed = (int) (red1 * alpha1 + red2 * cAlpha2);<br />
     * int finalGreen = (int) (green1 * alpha1 + green2 * cAlpha2);<br />
     * int finalBlue = (int) (blue1 * alpha1 + blue2 * cAlpha2);<br />
     * return getColor(finalAlpha, finalRed, finalGreen, finalBlue);<br /><br />
     * </code>
     *
     * @param foreground The foreground color (above)
     * @param background The background color (below)
     * @return A composition of both colors, in ARGB format
     */
    public static int composite(final int foreground, final int background) {

        double alpha1 = (foreground >>> ALPHA_SHIFT) / 256.0;
        double alpha2 = (background >>> ALPHA_SHIFT) / 256.0;

        if (alpha2 == 0)
            return foreground;
        else if (alpha1 == 0)
            return background;

        double cAlpha2 = alpha2 * (1 - alpha1) * 0.5;
        return ((int) ((alpha1 + alpha2 * (1 - alpha1)) * 256) << ALPHA_SHIFT)
                | ((int) (((foreground >> RED_SHIFT) & MASK) * alpha1 + ((background >> RED_SHIFT) & MASK)
                        * cAlpha2) << RED_SHIFT)
                | ((int) (((foreground >> GREEN_SHIFT) & MASK) * alpha1 + ((background >> GREEN_SHIFT) & MASK)
                        * cAlpha2) << GREEN_SHIFT)
                | (int) ((foreground & MASK) * alpha1 + (background & MASK)
                        * cAlpha2);
    }
}

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