pixelgrabber.java

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/*
 * @(#)PixelGrabber.java	1.22 03/01/23
 *
 * Copyright 2003 Sun Microsystems, Inc. All rights reserved.
 * SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 */

package java.awt.image;

import java.util.Hashtable;
import java.awt.image.ImageProducer;
import java.awt.image.ImageConsumer;
import java.awt.image.ColorModel;
import java.awt.Image;

/**
 * The PixelGrabber class implements an ImageConsumer which can be attached
 * to an Image or ImageProducer object to retrieve a subset of the pixels
 * in that image.  Here is an example:
 * <pre>
 *
 * public void handlesinglepixel(int x, int y, int pixel) {
 *	int alpha = (pixel >> 24) & 0xff;
 *	int red   = (pixel >> 16) & 0xff;
 *	int green = (pixel >>  8) & 0xff;
 *	int blue  = (pixel      ) & 0xff;
 *	// Deal with the pixel as necessary...
 * }
 *
 * public void handlepixels(Image img, int x, int y, int w, int h) {
 *	int[] pixels = new int[w * h];
 *	PixelGrabber pg = new PixelGrabber(img, x, y, w, h, pixels, 0, w);
 *	try {
 *	    pg.grabPixels();
 *	} catch (InterruptedException e) {
 *	    System.err.println("interrupted waiting for pixels!");
 *	    return;
 *	}
 *	if ((pg.getStatus() & ImageObserver.ABORT) != 0) {
 *	    System.err.println("image fetch aborted or errored");
 *	    return;
 *	}
 *	for (int j = 0; j < h; j++) {
 *	    for (int i = 0; i < w; i++) {
 *		handlesinglepixel(x+i, y+j, pixels[j * w + i]);
 *	    }
 *	}
 * }
 *
 * </pre>
 *
 * @see ColorModel#getRGBdefault
 *
 * @version 	1.22, 01/23/03
 * @author 	Jim Graham
 */
public class PixelGrabber implements ImageConsumer {
    ImageProducer producer;

    int dstX;
    int dstY;
    int dstW;
    int dstH;

    ColorModel imageModel;
    byte[] bytePixels;
    int[] intPixels;
    int dstOff;
    int dstScan;

    private boolean grabbing;
    private int flags;

    private static final int GRABBEDBITS = (ImageObserver.FRAMEBITS
					    | ImageObserver.ALLBITS);
    private static final int DONEBITS = (GRABBEDBITS
					 | ImageObserver.ERROR);

    /**
     * Create a PixelGrabber object to grab the (x, y, w, h) rectangular
     * section of pixels from the specified image into the given array.
     * The pixels are stored into the array in the default RGB ColorModel.
     * The RGB data for pixel (i, j) where (i, j) is inside the rectangle
     * (x, y, w, h) is stored in the array at
     * <tt>pix[(j - y) * scansize + (i - x) + off]</tt>.
     * @see ColorModel#getRGBdefault
     * @param img the image to retrieve pixels from
     * @param x the x coordinate of the upper left corner of the rectangle
     * of pixels to retrieve from the image, relative to the default
     * (unscaled) size of the image
     * @param y the y coordinate of the upper left corner of the rectangle
     * of pixels to retrieve from the image
     * @param w the width of the rectangle of pixels to retrieve
     * @param h the height of the rectangle of pixels to retrieve
     * @param pix the array of integers which are to be used to hold the
     * RGB pixels retrieved from the image
     * @param off the offset into the array of where to store the first pixel
     * @param scansize the distance from one row of pixels to the next in
     * the array
     */
    public PixelGrabber(Image img, int x, int y, int w, int h,
			int[] pix, int off, int scansize) {
	this(img.getSource(), x, y, w, h, pix, off, scansize);
    }

    /**
     * Create a PixelGrabber object to grab the (x, y, w, h) rectangular
     * section of pixels from the image produced by the specified
     * ImageProducer into the given array.
     * The pixels are stored into the array in the default RGB ColorModel.
     * The RGB data for pixel (i, j) where (i, j) is inside the rectangle
     * (x, y, w, h) is stored in the array at
     * <tt>pix[(j - y) * scansize + (i - x) + off]</tt>.
     * @param ip the <code>ImageProducer</code> that produces the 
     * image from which to retrieve pixels
     * @param x the x coordinate of the upper left corner of the rectangle
     * of pixels to retrieve from the image, relative to the default
     * (unscaled) size of the image
     * @param y the y coordinate of the upper left corner of the rectangle
     * of pixels to retrieve from the image
     * @param w the width of the rectangle of pixels to retrieve
     * @param h the height of the rectangle of pixels to retrieve
     * @param pix the array of integers which are to be used to hold the
     * RGB pixels retrieved from the image
     * @param off the offset into the array of where to store the first pixel
     * @param scansize the distance from one row of pixels to the next in
     * the array
     * @see ColorModel#getRGBdefault
     */
    public PixelGrabber(ImageProducer ip, int x, int y, int w, int h,
			int[] pix, int off, int scansize) {
	producer = ip;
	dstX = x;
	dstY = y;
	dstW = w;
	dstH = h;
	dstOff = off;
	dstScan = scansize;
	intPixels = pix;
	imageModel = ColorModel.getRGBdefault();
    }

    /**
     * Create a PixelGrabber object to grab the (x, y, w, h) rectangular
     * section of pixels from the specified image.  The pixels are
     * accumulated in the original ColorModel if the same ColorModel
     * is used for every call to setPixels, otherwise the pixels are
     * accumulated in the default RGB ColorModel.  If the forceRGB
     * parameter is true, then the pixels will be accumulated in the
     * default RGB ColorModel anyway.  A buffer is allocated by the
     * PixelGrabber to hold the pixels in either case.  If (w < 0) or
     * (h < 0), then they will default to the remaining width and
     * height of the source data when that information is delivered.
     * @param img the image to retrieve the image data from
     * @param x the x coordinate of the upper left corner of the rectangle
     * of pixels to retrieve from the image, relative to the default
     * (unscaled) size of the image
     * @param y the y coordinate of the upper left corner of the rectangle
     * of pixels to retrieve from the image
     * @param w the width of the rectangle of pixels to retrieve
     * @param h the height of the rectangle of pixels to retrieve
     * @param forceRGB true if the pixels should always be converted to
     * the default RGB ColorModel
     */
    public PixelGrabber(Image img, int x, int y, int w, int h,
			boolean forceRGB)
    {
	producer = img.getSource();
	dstX = x;
	dstY = y;
	dstW = w;
	dstH = h;
	if (forceRGB) {
	    imageModel = ColorModel.getRGBdefault();
	}
    }

    /**
     * Request the PixelGrabber to start fetching the pixels.
     */
    public synchronized void startGrabbing() {
	if ((flags & DONEBITS) != 0) {
	    return;
	}
	if (!grabbing) {
	    grabbing = true;
	    flags &= ~(ImageObserver.ABORT);
	    producer.startProduction(this);
	}
    }

    /**
     * Request the PixelGrabber to abort the image fetch.
     */
    public synchronized void abortGrabbing() {
	imageComplete(IMAGEABORTED);
    }

    /**
     * Request the Image or ImageProducer to start delivering pixels and
     * wait for all of the pixels in the rectangle of interest to be
     * delivered.
     * @return true if the pixels were successfully grabbed, false on
     * abort, error or timeout
     * @exception InterruptedException
     *            Another thread has interrupted this thread.
     */
    public boolean grabPixels() throws InterruptedException {
	return grabPixels(0);
    }

    /**
     * Request the Image or ImageProducer to start delivering pixels and
     * wait for all of the pixels in the rectangle of interest to be
     * delivered or until the specified timeout has elapsed.  This method
     * behaves in the following ways, depending on the value of 
     * <code>ms</code>:
     * <ul>
     * <li> If <code>ms</code> == 0, waits until all pixels are delivered
     * <li> If <code>ms</code> > 0, waits until all pixels are delivered 
     * as timeout expires.
     * <li> If <code>ms</code> < 0, returns <code>true</code> if all pixels 
     * are grabbed, <code>false</code> otherwise and does not wait.
     * </ul>
     * @param ms the number of milliseconds to wait for the image pixels
     * to arrive before timing out
     * @return true if the pixels were successfully grabbed, false on
     * abort, error or timeout
     * @exception InterruptedException
     *            Another thread has interrupted this thread.
     */
    public synchronized boolean grabPixels(long ms)
	throws InterruptedException
    {
	if ((flags & DONEBITS) != 0) {
	    return (flags & GRABBEDBITS) != 0;
	}
	long end = ms + System.currentTimeMillis();
	if (!grabbing) {
	    grabbing = true;
	    flags &= ~(ImageObserver.ABORT);
	    producer.startProduction(this);
	}
	while (grabbing) {
	    long timeout;
	    if (ms == 0) {
		timeout = 0;
	    } else {
		timeout = end - System.currentTimeMillis();
		if (timeout <= 0) {
		    break;
		}
	    }
	    wait(timeout);
	}
	return (flags & GRABBEDBITS) != 0;
    }

    /**
     * Return the status of the pixels.  The ImageObserver flags
     * representing the available pixel information are returned.
     * @return the bitwise OR of all relevant ImageObserver flags
     * @see ImageObserver
     */
    public synchronized int getStatus() {
	return flags;
    }

    /**
     * Get the width of the pixel buffer (after adjusting for image width).
     * If no width was specified for the rectangle of pixels to grab then
     * then this information will only be available after the image has
     * delivered the dimensions.
     * @return the final width used for the pixel buffer or -1 if the width
     * is not yet known
     * @see #getStatus
     */
    public synchronized int getWidth() {
	return (dstW < 0) ? -1 : dstW;
    }

    /**
     * Get the height of the pixel buffer (after adjusting for image height).
     * If no width was specified for the rectangle of pixels to grab then
     * then this information will only be available after the image has
     * delivered the dimensions.
     * @return the final height used for the pixel buffer or -1 if the height
     * is not yet known
     * @see #getStatus
     */
    public synchronized int getHeight() {
	return (dstH < 0) ? -1 : dstH;
    }

    /**
     * Get the pixel buffer.  If the PixelGrabber was not constructed
     * with an explicit pixel buffer to hold the pixels then this method
     * will return null until the size and format of the image data is
     * known.
     * Since the PixelGrabber may fall back on accumulating the data
     * in the default RGB ColorModel at any time if the source image
     * uses more than one ColorModel to deliver the data, the array
     * object returned by this method may change over time until the
     * image grab is complete.
     * @return either a byte array or an int array
     * @see #getStatus
     * @see #setPixels(int, int, int, int, ColorModel, byte[], int, int)
     * @see #setPixels(int, int, int, int, ColorModel, int[], int, int)
     */
    public synchronized Object getPixels() {
	return (bytePixels == null)
	    ? ((Object) intPixels)
	    : ((Object) bytePixels);
    }

    /**
     * Get the ColorModel for the pixels stored in the array.  If the
     * PixelGrabber was constructed with an explicit pixel buffer then
     * this method will always return the default RGB ColorModel,
     * otherwise it may return null until the ColorModel used by the
     * ImageProducer is known.
     * Since the PixelGrabber may fall back on accumulating the data
     * in the default RGB ColorModel at any time if the source image
     * uses more than one ColorModel to deliver the data, the ColorModel
     * object returned by this method may change over time until the
     * image grab is complete and may not reflect any of the ColorModel