Java Color Contrast contrastColorByShift(Color color, int shift)

Description

Create a contrasting RGB color to a color by shifting the color (making it brighter or darker) so that if used as foreground/background they are different enough to be readable.

License

Open Source License

Parameter

Parameter	Description
color	the color we want to create a contrast for
shift	the shift value

Return

the contrast color

Declaration

public static Color contrastColorByShift(Color color, int shift)

Method Source Code


//package com.java2s;
/*// ww  w .j a  va 2 s  . c  o  m
 * Copyright (C) 2015 Dieter J Kybelksties
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
 *
 * @date: 2015-12-16
 * @author: Dieter J Kybelksties
 */

import java.awt.Color;

public class Main {
    /**
     * Create a contrasting RGB color to a color by shifting the color (making
     * it brighter or darker) so that if used as foreground/background they are
     * different enough to be readable.
     *
     * @param color the color we want to create a contrast for
     * @param shift the shift value
     * @return the contrast color
     */
    public static Color contrastColorByShift(Color color, int shift) {
        float alpha = (color == null) ? 1.0F : color.getAlpha() / 256.0F;
        if (color == null) {
            color = Color.BLACK;
        }

        if (shift < 1) {
            shift = 128;
        }

        int r1 = color.getRed();
        int g1 = color.getGreen();
        int b1 = color.getBlue();
        float r2 = (float) ((r1 + shift) % 256) / 256.0F;
        float g2 = (float) ((g1 + shift) % 256) / 256.0F;
        float b2 = (float) ((b1 + shift) % 256) / 256.0F;

        Color reval = makeColor(r2, g2, b2, alpha);

        return reval;
    }

    /**
     * Create a color with RGB values and by ensuring they are in legal range
     * [0..255].
     *
     * @param r red
     * @param g green
     * @param b blue
     * @return the color object
     */
    public static Color makeColor(int r, int g, int b) {
        r = (r < 0) ? 0 : r;
        r = (r > 255) ? 255 : r;
        g = (g < 0) ? 0 : g;
        g = (g > 255) ? 255 : g;
        b = (b < 0) ? 0 : b;
        b = (b > 255) ? 255 : b;
        return new Color(r, g, b);
    }

    /**
     * Create a color with RGB values and by ensuring they are in legal range
     * [0..255].
     *
     * @param r red
     * @param g green
     * @param b blue
     * @param a transparency
     * @return the color object
     */
    public static Color makeColor(float r, float g, float b, float a) {
        r = (r < 0.0F) ? 0.0F : r;
        r = (r > 1.0F) ? 1.0F : r;
        g = (g < 0.0F) ? 0.0F : g;
        g = (g > 1.0F) ? 1.0F : g;
        b = (b < 0.0F) ? 0.0F : b;
        b = (b > 1.0F) ? 1.0F : b;
        a = (a < 0.0F) ? 0.0F : a;
        a = (a > 1.0F) ? 1.0F : a;
        return new Color(r, g, b, a);
    }
}