ColorUtil.java

package net.tasksnow.util;

import android.graphics.Color;


/**
 * @author D056943
 * @since 16:38:57 - 19.12.2012
 * @project cFoldersDemo
 */
public class ColorUtil {

    // ===========================================================
    // Constants
    // ===========================================================
    private static final int BRIGHTNESS_THRESHOLD = 130;
    private static float colorDiff = 0.18f;

    // ===========================================================
    // Constructors
    // ===========================================================
    private ColorUtil() {
    }

    // ===========================================================
    // Methods
    // ===========================================================

    /**
     * Calculate whether a color is light or dark, based on a commonly known
     * brightness formula.
     * 
     * @see {@literal http://en.wikipedia.org/wiki/HSV_color_space%23Lightness}
     */
    public static boolean isColorDark(int color) {
        return (((30 * Color.red(color)) + (59 * Color.green(color)) + (11 * Color.blue(color))) / 100) <= BRIGHTNESS_THRESHOLD;
    }

    public static int darkerColor(int color) {
        return changeColor(color, 1f - colorDiff);
    }

    public static int lighterColor(int color) {
        return changeColor(color, 1f + colorDiff);
    }

    public static int changeColor(int color, float multiplier) {
        int red = Color.red(color);
        int blue = Color.blue(color);
        int green = Color.green(color);

        return Color.rgb((int) (red * multiplier), (int) (green * multiplier), (int) (blue * multiplier));
    }

    public static int setAlpha(int color, int alpha) {

        int red = Color.red(color);
        int blue = Color.blue(color);
        int green = Color.green(color);

        return Color.argb(alpha, red, green, blue);
    }
}