pngencoderb.java

PngEncoder - convert a Java Image to PNG PngEncoderB - convert a Java BufferedImage to PNG

package com.keypoint;

import java.awt.Image;
import java.awt.image.BufferedImage;
import java.awt.image.DataBuffer;
import java.awt.image.IndexColorModel;
import java.awt.image.ImageObserver;
import java.awt.image.PixelGrabber;
import java.awt.image.WritableRaster;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.util.zip.CRC32;
import java.util.zip.Deflater;
import java.util.zip.DeflaterOutputStream;

/**
 * PngEncoderB takes a Java BufferedImage object and creates a byte string which can be saved as a PNG file.
 * The encoder will accept BufferedImages with eight-bit samples
 * or 4-byte ARGB samples. 
 * 
 * <p>There is also code to handle 4-byte samples returned as
 * one int per pixel, but that has not been tested.</p>
 *
 * <p>Thanks to Jay Denny at KeyPoint Software
 *    <code>http://www.keypoint.com/</code>
 * who let me develop this code on company time.</p>
 *
 * <p>You may contact me with (probably very-much-needed) improvements,
 * comments, and bug fixes at:</p>
 *
 *   <p><code>[e-mail]</code></p>
 *
 * <p>This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.<p>
 * 
 * <p>This library 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
 * Lesser General Public License for more details.</p>
 * 
 * <p>You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 * A copy of the GNU LGPL may be found at
 * <code>http://www.gnu.org/copyleft/lesser.html</code></p>
 *
 * @author J. David Eisenberg
 * @version 1.5, 19 Oct 2003
 *
 * CHANGES:
 * --------
 * 19-Sep-2003 : Fix for platforms using EBCDIC (contributed by Paulo Soares);
 * 19-Oct-2003 : Change private fields to protected fields so that
 *               PngEncoderB can inherit them (JDE)
 *				 Fixed bug with calculation of nRows
 *				 Added modifications for unsigned short images
 *					(contributed by Christian at xpogen.com) 
 */

public class PngEncoderB extends PngEncoder 
{

	/** PLTE tag. */
	private static final byte PLTE[] = { 80, 76, 84, 69 };

    protected BufferedImage image;
    protected WritableRaster wRaster;
    protected int tType;

    /**
     * Class constructor
     *
     */
    public PngEncoderB()
    {
        this( null, false, FILTER_NONE, 0 );
    }

    /**
     * Class constructor specifying BufferedImage to encode, with no alpha channel encoding.
     *
     * @param image A Java BufferedImage object
     */
    public PngEncoderB( BufferedImage image )
    {
        this(image, false, FILTER_NONE, 0);
    }

    /**
     * Class constructor specifying BufferedImage to encode, and whether to encode alpha.
     *
     * @param image A Java BufferedImage object
     * @param encodeAlpha Encode the alpha channel? false=no; true=yes
     */
    public PngEncoderB( BufferedImage image, boolean encodeAlpha )
    {
        this( image, encodeAlpha, FILTER_NONE, 0 );
    }

    /**
     * Class constructor specifying BufferedImage to encode, whether to encode alpha, and filter to use.
     *
     * @param image A Java BufferedImage object
     * @param encodeAlpha Encode the alpha channel? false=no; true=yes
     * @param whichFilter 0=none, 1=sub, 2=up
     */
    public PngEncoderB( BufferedImage image, boolean encodeAlpha,
       int whichFilter )
    {
        this( image, encodeAlpha, whichFilter, 0 );
    }

    /**
     * Class constructor specifying BufferedImage source to encode, whether to encode alpha, filter to use, and compression level
     *
     * @param image A Java BufferedImage object
     * @param encodeAlpha Encode the alpha channel? false=no; true=yes
     * @param whichFilter 0=none, 1=sub, 2=up
     * @param compLevel 0..9
     */
    public PngEncoderB( BufferedImage image, boolean encodeAlpha,
      int whichFilter, int compLevel )
    {
        this.image = image;
        this.encodeAlpha = encodeAlpha;
        setFilter( whichFilter );
        if (compLevel >=0 && compLevel <=9)
        {
            this.compressionLevel = compLevel;
        }
    }

    /**
     * Set the BufferedImage to be encoded
     *
     * @param BufferedImage A Java BufferedImage object
     */
    public void setImage( BufferedImage image )
    {
        this.image = image;
        pngBytes = null;
    }

    /**
     * Creates an array of bytes that is the PNG equivalent of the current image, specifying whether to encode alpha or not.
     *
     * @param encodeAlpha boolean false=no alpha, true=encode alpha
     * @return an array of bytes, or null if there was a problem
     */
    public byte[] pngEncode( boolean encodeAlpha )
    {
        byte[]  pngIdBytes = { -119, 80, 78, 71, 13, 10, 26, 10 };
        int     i;

        if (image == null)
        {
            System.err.println("pngEncode: image is null; returning null");
			return null;
        }
        width = image.getWidth( null );
        height = image.getHeight( null );
        this.image = image;

        if (!establishStorageInfo())
        {
			System.err.println("pngEncode: cannot establish storage info");
            return null;
        }
        
        /*
         * start with an array that is big enough to hold all the pixels
         * (plus filter bytes), and an extra 200 bytes for header info
         */
        pngBytes = new byte[((width+1) * height * 3) + 200];

        /*
         * keep track of largest byte written to the array
         */
        maxPos = 0;

        bytePos = writeBytes( pngIdBytes, 0 );
 //       hdrPos = bytePos;
        writeHeader();
//        dataPos = bytePos;
        if (writeImageData())
        {
            writeEnd();
            pngBytes = resizeByteArray( pngBytes, maxPos );
        }
        else
        {
			System.err.println("pngEncode: writeImageData failed => null");
            pngBytes = null;
        }
        return pngBytes;
    }

    /**
     * Creates an array of bytes that is the PNG equivalent of the current image.
     * Alpha encoding is determined by its setting in the constructor.
     *
     * @return an array of bytes, or null if there was a problem
     */
    public byte[] pngEncode()
    {
        return pngEncode( encodeAlpha );
    }

    /**
     * 
     * Get and set variables that determine how picture is stored.
     *
     * Retrieves the writable raster of the buffered image,
     * as well its transfer type.
     *
     * Sets number of output bytes per pixel, and, if only
     * eight-bit bytes, turns off alpha encoding.
     * @return true if 1-byte or 4-byte data, false otherwise
     */
    protected boolean establishStorageInfo()
    {
        int dataBytes;
    
        wRaster = image.getRaster();
        dataBytes = wRaster.getNumDataElements();
        tType = wRaster.getTransferType();

		if (((tType == DataBuffer.TYPE_BYTE  ) && (dataBytes == 4)) ||
			((tType == DataBuffer.TYPE_INT   ) && (dataBytes == 1)) ||
           // on Win 2k/ME, tType == 1, dataBytes == 1
			((tType == DataBuffer.TYPE_USHORT) && (dataBytes == 1)) )
        {
            bytesPerPixel = (encodeAlpha) ? 4 : 3;
        }
        else if ((tType == DataBuffer.TYPE_BYTE) && (dataBytes == 1))
        {
            bytesPerPixel = 1;
            encodeAlpha = false;    // one-byte samples
        }
        else
		{
			System.err.println("PNG encoder cannot establish storage info:");
			System.err.println("  TransferType == " + tType );
			System.err.println("  NumDataElements == " + dataBytes);
			return false;
		}
        return true;
    }

    /**
     * Write a PNG "IHDR" chunk into the pngBytes array.
     */