ImageAnimation.java

/*
 * Copyright (C) 2019 John Glenn Neffenger
 *
 * 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 3 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, see <http://www.gnu.org/licenses/>.
 */
package org.status6.epd.javafx;

import java.awt.Graphics2D;
import java.awt.image.BufferedImage;
import java.awt.image.DataBufferInt;
import java.io.IOException;
import java.nio.IntBuffer;
import java.util.ArrayList;
import javafx.scene.image.ImageView;
import javafx.scene.image.PixelFormat;
import javafx.scene.image.WritableImage;
import javax.imageio.ImageIO;
import javax.imageio.ImageReader;

/**
 * An animation timer that cycles through the sequence of frames in an animated
 * GIF image file.
 *
 * @author John Neffenger
 */
class ImageAnimation extends FiniteAnimation {

    private static final String FORMAT_NAME = "gif";

    private final ArrayList<BufferedImage> frames;
    private final ImageView view;
    private final boolean patrol;
    private final int count;
    private final int width;
    private final int height;
    private final BufferedImage awtImage;
    private final Graphics2D graphics;
    private final PixelFormat<IntBuffer> format;
    private final WritableImage jfxImage1;
    private final WritableImage jfxImage2;

    private WritableImage jfxImage;
    private boolean reverse;
    private int index;

    /**
     * Gets a list of all animation frames in the GIF image.
     *
     * @param filename the name of the image file
     * @return the list of animation frames in the image
     * @throws IOException if an error occurs reading the image file
     * @throws IllegalArgumentException if the image format is not GIF
     */
    private static ArrayList<BufferedImage> getFrames(String filename) throws IOException {
        ArrayList<BufferedImage> list = new ArrayList<>();
        try (var input = ImageAnimation.class.getResourceAsStream("/" + filename)) {
            if (input == null) {
                throw new IOException(String.format(
                        "Failed loading image file: %s", filename));
            }
            try (var stream = ImageIO.createImageInputStream(input)) {
                ImageReader reader = ImageIO.getImageReadersByFormatName(FORMAT_NAME).next();
                reader.setInput(stream);
                int count = reader.getNumImages(true);
                if (count == 0) {
                    throw new IllegalArgumentException(String.format(
                            "Failed reading GIF image: %s", filename));
                }
                for (int i = 0; i < count; i++) {
                    list.add(reader.read(i));
                }
            }
        }
        return list;
    }

    /**
     * Creates a new image animation.
     *
     * @param view the node for painting each animation frame
     * @param filename the name of the image file
     * @param patrol {@code true} to cycle back and forth between the first and
     * last frames of the animation, called a <i>patrol cycle</i>; otherwise
     * {@code false} to loop back to the first frame after the last
     * @throws IOException if an error occurs reading the image file
     */
    ImageAnimation(ImageView view, String filename, boolean patrol) throws IOException {
        frames = getFrames(filename);
        this.view = view;
        this.patrol = patrol;
        count = frames.size();
        BufferedImage first = frames.get(0);
        width = first.getWidth();
        height = first.getHeight();
        for (BufferedImage image : frames) {
            if (image.getWidth() != width || image.getHeight() != height) {
                throw new IllegalArgumentException("GIF image must be a coalesced animation");
            }
        }

        /*
         * The fastest image conversion draws the source AWT image into an
         * intermediate AWT image of type INT_ARGB; then gets the intermediate
         * raster data and writes it to the target JavaFX image as pixels in the
         * INT_ARGB_PRE format (see https://github.com/jgneff/tofximage).
         * Because pixels in GIF images are either fully opaque or fully
         * transparent, their colors are the same whether or not premultiplied
         * with alpha.
         */
        awtImage = new BufferedImage(width, height, BufferedImage.TYPE_INT_ARGB);
        graphics = awtImage.createGraphics();
        format = PixelFormat.getIntArgbPreInstance();

        /*
         * Use double buffering on the JavaFX Application Thread to avoid
         * modifying an image in use by the QuantumRenderer thread; otherwise,
         * screen tearing is visible when there is enough competition with other
         * threads in the Java virtual machine.
         */
        jfxImage1 = new WritableImage(width, height);
        jfxImage2 = new WritableImage(width, height);
        jfxImage = jfxImage1;
    }

    /**
     * Gets the index for the next frame when in a patrol cycle.
     *
     * @return the index for the next frame
     */
    private int nextPatrolCycle() {
        int next = reverse ? index - 1 : index + 1;
        if (next < 0) {
            next = 1;
            reverse = false;
        } else if (next == count) {
            next = count - 2;
            reverse = true;
        }
        return next;
    }

    /**
     * Gets the index for the next frame when in a loop cycle.
     *
     * @return the index for the next frame
     */
    private int nextLoopCycle() {
        int next = index + 1;
        if (next == count) {
            next = 0;
        }
        return next;
    }

    @Override
    int getNumFrames() {
        return frames.size();
    }

    @Override
    public void handle(long now) {
        graphics.drawImage(frames.get(index), 0, 0, null);  // Draws into awtImage
        int[] data = ((DataBufferInt) awtImage.getRaster().getDataBuffer()).getData();
        jfxImage.getPixelWriter().setPixels(0, 0, width, height, format, data, 0, width);
        view.setImage(jfxImage);
        jfxImage = jfxImage == jfxImage2 ? jfxImage1 : jfxImage2;
        index = patrol ? nextPatrolCycle() : nextLoopCycle();
    }
}