imageencoder.java

图像文件分析

// ImageEncoder - abstract class for writing out 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.Encoders;

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

/// Abstract class for writing out an image.
// <P>
// A framework for classes that encode and write out an image in
// a particular file format.
// <P>
// This provides a simplified rendition of the ImageConsumer interface.
// It always delivers the pixels as ints in the RGBdefault color model.
// It always provides them in top-down left-right order.
// If you want more flexibility you can always implement ImageConsumer
// directly.
// <P>
// <A HREF="/resources/classes/Acme/JPM/Encoders/ImageEncoder.java">Fetch the software.</A><BR>
// <A HREF="/resources/classes/Acme.tar.gz">Fetch the entire Acme package.</A>
// <P>
// @see GifEncoder
// @see PpmEncoder
// @see Acme.JPM.Decoders.ImageDecoder

public abstract class ImageEncoder implements ImageConsumer
    {

    protected OutputStream out;

    private ImageProducer producer;
    private int width = -1;
    private int height = -1;
    private int hintflags = 0;
    private boolean started = false;
    private boolean encoding;
    private IOException iox;
    private static final ColorModel rgbModel = ColorModel.getRGBdefault();
    private Hashtable props = null;

    /// Constructor.
    // @param img The image to encode.
    // @param out The stream to write the bytes to.
    public ImageEncoder( Image img, OutputStream out ) throws IOException
	{
	this( img.getSource(), out );
	}

    /// Constructor.
    // @param producer The ImageProducer to encode.
    // @param out The stream to write the bytes to.
    public ImageEncoder( ImageProducer producer, OutputStream out ) throws IOException
	{
	this.producer = producer;
	this.out = out;
	}


    // Methods that subclasses implement.

    /// Subclasses implement this to initialize an encoding.
    abstract void encodeStart( int w, int h ) throws IOException;

    /// Subclasses implement this to actually write out some bits.  They
    // are guaranteed to be delivered in top-down-left-right order.
    // One int per pixel, index is row * scansize + off + col,
    // RGBdefault (AARRGGBB) color model.
    abstract void encodePixels(
	int x, int y, int w, int h, int[] rgbPixels, int off, int scansize )
	throws IOException;

    /// Subclasses implement this to finish an encoding.
    abstract void encodeDone() throws IOException;


    // Our own methods.

    /// Call this after initialization to get things going.
    public synchronized void encode() throws IOException
	{
	encoding = true;
	iox = null;
	producer.startProduction( this );
	while ( encoding )
	    try
		{
		wait();
		}
	    catch ( InterruptedException e ) {}
	if ( iox != null )
	    throw iox;
	}

    private boolean accumulate = false;
    private int[] accumulator;

    private void encodePixelsWrapper(
	int x, int y, int w, int h, int[] rgbPixels, int off, int scansize )
	throws IOException
	{
	if ( ! started )
	    {
	    started = true;
	    encodeStart( width, height );
	    if ( ( hintflags & TOPDOWNLEFTRIGHT ) == 0 )
		{
		accumulate = true;
		accumulator = new int[width * height];
		}
	    }
	if ( accumulate )
	    for ( int row = 0; row < h; ++row )
		System.arraycopy(
		    rgbPixels, row * scansize + off,
		    accumulator, ( y + row ) * width + x,
		    w );
	else
	    encodePixels( x, y, w, h, rgbPixels, off, scansize );
	}

    private void encodeFinish() throws IOException
	{
	if ( accumulate )
	    {
	    encodePixels( 0, 0, width, height, accumulator, 0, width );
	    accumulator = null;
	    accumulate = false;
	    }
	}

    private synchronized void stop()
	{
	encoding = false;
	notifyAll();
	}


    // Methods from ImageConsumer.

    public void setDimensions( int width, int height )
	{
	this.width = width;
	this.height = height;
	}

    public void setProperties( Hashtable props )
	{
	this.props = props;
	}

    public void setColorModel( ColorModel model )
	{
	// Ignore.
	}

    public void setHints( int hintflags )
	{
	this.hintflags = hintflags;
	}

    public void setPixels(
	int x, int y, int w, int h, ColorModel model, byte[] pixels,
	int off, int scansize )
	{
	int[] rgbPixels = new int[w];
	for ( int row = 0; row < h; ++row )
	    {
	    int rowOff = off + row * scansize;
	    for ( int col = 0; col < w; ++col )
		rgbPixels[col] = model.getRGB( pixels[rowOff + col] & 0xff );
	    try
		{
		encodePixelsWrapper( x, y + row, w, 1, rgbPixels, 0, w );
		}
	    catch ( IOException e )
		{
		iox = e;
		stop();
		return;
		}
	    }
	}

    public void setPixels(
	int x, int y, int w, int h, ColorModel model, int[] pixels,
	int off, int scansize )
	{
	if ( model == rgbModel )
	    {
	    try
		{
		encodePixelsWrapper( x, y, w, h, pixels, off, scansize );
		}
	    catch ( IOException e )
		{
		iox = e;
		stop();
		return;
		}
	    }
	else
	    {
	    int[] rgbPixels = new int[w];
            for ( int row = 0; row < h; ++row )
		{
		int rowOff = off + row * scansize;
                for ( int col = 0; col < w; ++col )
                    rgbPixels[col] = model.getRGB( pixels[rowOff + col] );
		try
		    {
		    encodePixelsWrapper( x, y + row, w, 1, rgbPixels, 0, w );
		    }
		catch ( IOException e )
		    {
		    iox = e;
		    stop();
		    return;
		    }
		}
	    }
	}

    public void imageComplete( int status )
	{
	producer.removeConsumer( this );
	if ( status == ImageConsumer.IMAGEABORTED )
	    iox = new IOException( "image aborted" );
	else
	    {
	    try
		{
		encodeFinish();
		encodeDone();
		}
	    catch ( IOException e )
		{
		iox = e;
		}
	    }
	stop();
	}

    }