imagedecoder.java

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// ImageDecoder - abstract class for reading in an image
//
// Copyright (C) 1996 by Jef Poskanzer <[e-mail]>.  All rights reserved.
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions
// are met:
// 1. Redistributions of source code must retain the above copyright
//    notice, this list of conditions and the following disclaimer.
// 2. Redistributions in binary form must reproduce the above copyright
//    notice, this list of conditions and the following disclaimer in the
//    documentation and/or other materials provided with the distribution.
//
// THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
// ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
// IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
// ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
// FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
// DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
// OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
// HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
// LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
// OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
// SUCH DAMAGE.
//
// Visit the ACME Labs Java page for up-to-date versions of this and other
// fine Java utilities: http://www.acme.com/java/

package Acme.JPM.Decoders;

import java.util.*;
import java.io.*;
import java.awt.image.*;

/// Abstract class for reading in an image.
// <P>
// A framework for classes that read in and decode an image in
// a particular file format.
// <P>
// This provides a very simplified rendition of the ImageProducer interface.
// It requires the decoder to read the image a row at a time.  It requires
// use of the RGBdefault color model.
// If you want more flexibility you can always implement ImageProducer
// directly.
// <P>
// <A HREF="/resources/classes/Acme/JPM/Decoders/ImageDecoder.java">Fetch the software.</A><BR>
// <A HREF="/resources/classes/Acme.tar.gz">Fetch the entire Acme package.</A>
// <P>
// @see PpmDecoder
// @see Acme.JPM.Encoders.ImageEncoder

public abstract class ImageDecoder implements ImageProducer
    {

    private InputStream in;
    private int width, height;
    private boolean[] rowsRead;
    private int[][] rgbPixels;
    private boolean startedRead = false;
    private boolean gotSize = false;
    private boolean err = false;
    private boolean producing = false;
    private Vector consumers = new Vector();
    private static final ColorModel model = ColorModel.getRGBdefault();


    /// Constructor.
    // @param in The stream to read the bytes from.
    public ImageDecoder( InputStream in )
	{
	this.in = in;
	}

    
    // Methods that subclasses implement.

    /// Subclasses implement this to read in enough of the image stream
    // to figure out the width and height.
    abstract void readHeader( InputStream in ) throws IOException;

    /// Subclasses implement this to return the width, or -1 if not known.
    abstract int getWidth();

    /// Subclasses implement this to return the height, or -1 if not known.
    abstract int getHeight();

    /// Subclasses implement this to read pixel data into the rgbRow
    // array, an int[width].  One int per pixel, no offsets or padding,
    // RGBdefault (AARRGGBB) color model.
    abstract void readRow( InputStream in, int row, int[] rgbRow ) throws IOException;


    // Our own methods.

    void readImage()
	{
	try
	    {
	    readHeader( in );
	    width = getWidth();
	    height = getHeight();
	    if ( width == -1 || height == -1 )
		err = true;
	    else
		{
		rowsRead = new boolean[height];
		for ( int row = 0; row < height; ++row )
		    rowsRead[row] = false;
		gotSize = true;
		notifyThem();
		rgbPixels = new int[height][width];
		for ( int row = 0; row < height; ++row )
		    {
		    readRow( in, row, rgbPixels[row] );
		    rowsRead[row] = true;
		    notifyThem();
		    }
		}
	    }
	catch ( IOException e )
	    {
	    err = true;
	    width = -1;
	    height = -1;
	    rowsRead = null;
	    rgbPixels = null;
	    }
	}

    private synchronized void notifyThem()
	{
	notifyAll();
	}

    void sendImage()
	{
	// Grab the list of consumers, in case it changes while we're sending.
	ImageConsumer[] c = new ImageConsumer[consumers.size()];
	int i;
	for ( i = 0; i < c.length; ++i )
	    c[i] = (ImageConsumer) consumers.elementAt( i );
	// Try to be as parallel as possible.
	waitForSize();
	for ( i = 0; i < c.length; ++i )
	    sendHead( c[i] );
	for ( int row = 0; row < height; ++row )
	    for ( i = 0; i < c.length; ++i )
		sendPixelRow( c[i], row );
	for ( i = 0; i < c.length; ++i )
	    sendTail( c[i] );
	producing = false;
	}

    private synchronized void waitForSize()
	{
	while ( ( ! err ) && ( ! gotSize  ))
	    {
	    try
		{
		wait();
		}
	    catch ( InterruptedException ignore ) {}
	    }
	}

    private synchronized void waitForRow( int row )
	{
	while ( ( ! err ) && ( ! rowsRead[row] ) )
	    {
	    try
		{
		wait();
		}
	    catch ( InterruptedException ignore ) {}
	    }
	}

    private void sendHead( ImageConsumer ic )
	{
	if ( err )
	    return;
	ic.setDimensions( width, height );
	ic.setColorModel( model );
	ic.setHints(
	    ImageConsumer.TOPDOWNLEFTRIGHT | ImageConsumer.COMPLETESCANLINES |
	    ImageConsumer.SINGLEPASS | ImageConsumer.SINGLEFRAME );
	}

    private void sendPixelRow( ImageConsumer ic, int row )
	{
	if ( err )
	    return;
	waitForRow( row );
	if ( err )
	    return;
	ic.setPixels( 0, row, width, 1, model, rgbPixels[row], 0, width );
	}

    private void sendTail( ImageConsumer ic )
	{
	if ( err )
	    ic.imageComplete( ImageConsumer.IMAGEERROR );
	else
	    ic.imageComplete( ImageConsumer.STATICIMAGEDONE );

	}


    // Methods from ImageProducer.

    /// This method is used to register an ImageConsumer with the
    // ImageProducer for access to the image data during a later
    // reconstruction of the Image.  The ImageProducer may, at its
    // discretion, start delivering the image data to the consumer
    // using the ImageConsumer interface immediately, or when the
    // next available image reconstruction is triggered by a call
    // to the startProduction method.
    // @see #startProduction
    public void addConsumer( ImageConsumer ic )
	{
	if ( ic != null && ! isConsumer( ic ) )
	    consumers.addElement( ic );
	}

    /// This method determines if a given ImageConsumer object
    // is currently registered with this ImageProducer as one
    // of its consumers.
    public boolean isConsumer( ImageConsumer ic )
	{
	return consumers.contains( ic );
	}

    /// This method removes the given ImageConsumer object
    // from the list of consumers currently registered to
    // receive image data.  It is not considered an error
    // to remove a consumer that is not currently registered.
    // The ImageProducer should stop sending data to this
    // consumer as soon as is feasible.
    public void removeConsumer( ImageConsumer ic )
	{
	consumers.removeElement( ic );
	}

    /// This method both registers the given ImageConsumer object
    // as a consumer and starts an immediate reconstruction of
    // the image data which will then be delivered to this
    // consumer and any other consumer which may have already
    // been registered with the producer.  This method differs
    // from the addConsumer method in that a reproduction of
    // the image data should be triggered as soon as possible.
    // @see #addConsumer
    public void startProduction( ImageConsumer ic )
	{
	addConsumer( ic );
	if ( ! startedRead )
	    {
	    startedRead = true;
	    new ImageDecoderRead( this );
	    }
	if ( ! producing )
	    {
	    producing = true;
	    sendImage();
	    }
	}

    /// This method is used by an ImageConsumer to request that
    // the ImageProducer attempt to resend the image data one
    // more time in TOPDOWNLEFTRIGHT order so that higher
    // quality conversion algorithms which depend on receiving
    // pixels in order can be used to produce a better output
    // version of the image.  The ImageProducer is free to
    // ignore this call if it cannot resend the data in that
    // order.  If the data can be resent, then the ImageProducer
    // should respond by executing the following minimum set of
    // ImageConsumer method calls:
    // <PRE>
    //     ic.setHints( TOPDOWNLEFTRIGHT | [otherhints] );
    //     ic.setPixels( [...] );    // as many times as needed
    //     ic.imageComplete( [status] );
    // </PRE>
    // @see ImageConsumer#setHints
    public void requestTopDownLeftRightResend( ImageConsumer ic )
	{
	addConsumer( ic );
	waitForSize();
	sendHead( ic );
	for ( int row = 0; row < height; ++row )
	    sendPixelRow( ic, row );
	sendTail( ic );
	}

    }


class ImageDecoderRead extends Thread
    {

    private ImageDecoder parent;

    public ImageDecoderRead( ImageDecoder parent )
	{
	this.parent = parent;
	start();
	}

    // Methods from Runnable.

    public void run()
	{
	parent.readImage();
	}

    }