gecko/mobile/android/base/gfx/CheckerboardImage.java

/* -*- Mode: Java; c-basic-offset: 4; tab-width: 20; indent-tabs-mode: nil; -*-
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 * Version: MPL 1.1/GPL 2.0/LGPL 2.1
 *
 * The contents of this file are subject to the Mozilla Public License Version
 * 1.1 (the "License"); you may not use this file except in compliance with
 * the License. You may obtain a copy of the License at
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 * Software distributed under the License is distributed on an "AS IS" basis,
 * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
 * for the specific language governing rights and limitations under the
 * License.
 *
 * The Original Code is Mozilla Android code.
 *
 * The Initial Developer of the Original Code is Mozilla Foundation.
 * Portions created by the Initial Developer are Copyright (C) 2012
 * the Initial Developer. All Rights Reserved.
 *
 * Contributor(s):
 *   Patrick Walton <pcwalton@mozilla.com>
 *
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 * either the GNU General Public License Version 2 or later (the "GPL"), or
 * the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
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package org.mozilla.gecko.gfx;

import org.mozilla.gecko.GeckoAppShell;
import android.graphics.Color;
import java.nio.ByteBuffer;
import java.nio.ShortBuffer;
import java.util.Arrays;

/** A Cairo image that displays a tinted checkerboard. */
public class CheckerboardImage extends CairoImage {
    // The width and height of the checkerboard tile.
    private static final int SIZE = 16;
    // The pixel format of the checkerboard tile.
    private static final int FORMAT = CairoImage.FORMAT_RGB16_565;
    // The color to mix in to tint the background color.
    private static final int TINT_COLOR = Color.GRAY;
    // The amount to mix in.
    private static final float TINT_OPACITY = 0.4f;

    private ByteBuffer mBuffer;
    private int mMainColor;

    /** Creates a new checkerboard image. */
    public CheckerboardImage() {
        int bpp = CairoUtils.bitsPerPixelForCairoFormat(FORMAT);
        mBuffer = GeckoAppShell.allocateDirectBuffer(SIZE * SIZE * bpp / 8);
        setColor(Color.WHITE);
    }

    /** Returns the current color of the checkerboard. */
    public int getColor() {
        return mMainColor;
    }

    /** Sets the color of the checkerboard image and regenerates it. */
    public void setColor(int color) {
        if (mMainColor == color) {
            return;
        }

        mMainColor = color;
        int tintColor = tint(mMainColor);
        short mainColor16 = convertTo16Bit(mMainColor), tintColor16 = convertTo16Bit(tintColor);

        short[] mainPattern = new short[SIZE / 2], tintPattern = new short[SIZE / 2];
        Arrays.fill(mainPattern, mainColor16);
        Arrays.fill(tintPattern, tintColor16);

        // The checkerboard pattern looks like this:
        //
        // +---+---+
        // | N | T |  N = normal
        // +---+---+  T = tinted
        // | T | N |
        // +---+---+

        mBuffer.rewind();
        ShortBuffer shortBuffer = mBuffer.asShortBuffer();
        for (int i = 0; i < SIZE / 2; i++) {
            shortBuffer.put(mainPattern);
            shortBuffer.put(tintPattern);
        }
        for (int i = SIZE / 2; i < SIZE; i++) {
            shortBuffer.put(tintPattern);
            shortBuffer.put(mainPattern);
        }
    }

    // Tints the given color appropriately and returns the tinted color.
    private int tint(int color) {
        float negTintOpacity = 1.0f - TINT_OPACITY;
        float r = Color.red(color) * negTintOpacity + Color.red(TINT_COLOR) * TINT_OPACITY;
        float g = Color.green(color) * negTintOpacity + Color.green(TINT_COLOR) * TINT_OPACITY;
        float b = Color.blue(color) * negTintOpacity + Color.blue(TINT_COLOR) * TINT_OPACITY;
        return Color.rgb(Math.round(r), Math.round(g), Math.round(b));
    }

    // Converts a 32-bit ARGB color to 16-bit R5G6B5, truncating values and discarding the alpha
    // channel.
    private short convertTo16Bit(int color) {
        int r = Color.red(color) >> 3, g = Color.green(color) >> 2, b = Color.blue(color) >> 3;
        int c = ((r << 11) | (g << 5) | b);
        // Swap endianness.
        return (short)((c >> 8) | ((c & 0xff) << 8));
    }

    @Override
    protected void finalize() throws Throwable {
        try {
            if (mBuffer != null) {
                GeckoAppShell.freeDirectBuffer(mBuffer);
            }
        } finally {
            super.finalize();
        }
    }

    @Override
    public ByteBuffer getBuffer() {
        return mBuffer;
    }

    @Override
    public IntSize getSize() {
        return new IntSize(SIZE, SIZE);
    }

    @Override
    public int getFormat() {
        return FORMAT;
    }
}