Creates a gradient of colors. - Android Graphics

Android examples for Graphics:Color

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Description

Creates a gradient of colors.

Demo Code

/*******************************************************************************
 * Copyright (c) 2011 MadRobot./*  ww w.  j  av a2 s.c o m*/
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the GNU Lesser Public License v2.1
 * which accompanies this distribution, and is available at
 * http://www.gnu.org/licenses/old-licenses/gpl-2.0.html
 * 
 * Contributors:
 *  Elton Kent - initial API and implementation
 ******************************************************************************/
//package com.java2s;

public class Main {
    /**
     * Creates a gradient of colors. This method is highly optimized and only
     * uses bit-shifting and additions (no multitplication nor devision), but it
     * will create a new integer array in each call.
     * 
     * @param startColor
     *            the first color
     * @param endColor
     *            the last color
     * @param steps
     *            the number of colors in the gradient, when 2 is given, the
     *            first one will be the startColor and the second one will the
     *            endColor.
     * @return an int array with the gradient.
     * 
     */
    public static final int[] getGradient(int startColor, int endColor,
            int steps) {
        int[] gradient = new int[steps];
        getGradient(startColor, endColor, gradient);
        return gradient;
    }

    /**
     * Creates a gradient of colors. This method is highly optimized and only
     * uses bit-shifting and additions (no multitplication nor devision).
     * 
     * @param startColor
     *            The first color
     * @param endColor
     *            The last color
     * @param gradient
     *            The array in which the gradient colors are stored. length of
     *            the array is the number of steps used in the gradient
     * 
     */
    public static final void getGradient(final int startColor,
            final int endColor, final int[] gradient) {
        int steps = gradient.length;
        if (steps == 0) {
            return;
        } else if (steps == 1) {
            gradient[0] = startColor;
            return;
        }
        int startAlpha = startColor >>> 24;
        int startRed = (startColor >>> 16) & 0x00FF;
        int startGreen = (startColor >>> 8) & 0x0000FF;
        int startBlue = startColor & 0x00000FF;

        final int endAlpha = endColor >>> 24;
        final int endRed = (endColor >>> 16) & 0x00FF;
        final int endGreen = (endColor >>> 8) & 0x0000FF;
        final int endBlue = endColor & 0x00000FF;

        final int stepAlpha = ((endAlpha - startAlpha) << 8) / (steps - 1);
        final int stepRed = ((endRed - startRed) << 8) / (steps - 1);
        final int stepGreen = ((endGreen - startGreen) << 8) / (steps - 1);
        final int stepBlue = ((endBlue - startBlue) << 8) / (steps - 1);
        startAlpha <<= 8;
        startRed <<= 8;
        startGreen <<= 8;
        startBlue <<= 8;

        gradient[0] = startColor;
        for (int i = 1; i < steps; i++) {
            startAlpha += stepAlpha;
            startRed += stepRed;
            startGreen += stepGreen;
            startBlue += stepBlue;

            gradient[i] = ((startAlpha << 16) & 0xFF000000)
                    | ((startRed << 8) & 0x00FF0000)
                    | (startGreen & 0x0000FF00) | (startBlue >>> 8);
            // | (( startBlue >>> 8) & 0x000000FF);
        }
    }
}

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