/*

 ============================================================================
                   The Apache Software License, Version 1.1
 ============================================================================

 Copyright (C) 1999-2003 The Apache Software Foundation. All rights reserved.

 Redistribution and use in source and binary forms, with or without modifica-
 tion, 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.

 3. The end-user documentation included with the redistribution, if any, must
    include  the following  acknowledgment:  "This product includes  software
    developed  by the  Apache Software Foundation  (http://www.apache.org/)."
    Alternately, this  acknowledgment may  appear in the software itself,  if
    and wherever such third-party acknowledgments normally appear.

 4. The names "Batik" and  "Apache Software Foundation" must  not  be
    used to  endorse or promote  products derived from  this software without
    prior written permission. For written permission, please contact
    apache@apache.org.

 5. Products  derived from this software may not  be called "Apache", nor may
    "Apache" appear  in their name,  without prior written permission  of the
    Apache Software Foundation.

 THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED 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
 APACHE SOFTWARE  FOUNDATION  OR ITS CONTRIBUTORS  BE LIABLE FOR  ANY DIRECT,
 INDIRECT, INCIDENTAL, SPECIAL,  EXEMPLARY, OR CONSEQUENTIAL  DAMAGES (INCLU-
 DING, 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.

 This software  consists of voluntary contributions made  by many individuals
 on  behalf of the Apache Software  Foundation. For more  information on the
 Apache Software Foundation, please see <http://www.apache.org/>.

*/

package org.apache.batik.ext.awt.image.codec;

import java.awt.Color;
import java.awt.Point;
import java.awt.Rectangle;
import java.awt.Transparency;
import java.awt.color.ColorSpace;
import java.awt.image.ColorModel;
import java.awt.image.ComponentColorModel;
import java.awt.image.DataBuffer;
import java.awt.image.DataBufferByte;
import java.awt.image.DataBufferUShort;
import java.awt.image.IndexColorModel;
import java.awt.image.Raster;
import java.awt.image.SampleModel;
import java.awt.image.WritableRaster;
import java.io.BufferedInputStream;
import java.io.ByteArrayInputStream;
import java.io.DataInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.SequenceInputStream;
import java.util.Date;
import java.util.GregorianCalendar;
import java.util.Hashtable;
import java.util.TimeZone;
import java.util.Vector;
import java.util.zip.Inflater;
import java.util.zip.InflaterInputStream;

import org.apache.batik.ext.awt.image.GraphicsUtil;
import org.apache.batik.ext.awt.image.rendered.AbstractRed;
import org.apache.batik.ext.awt.image.rendered.CachableRed;

public class PNGRed extends AbstractRed {

    static class PNGChunk {
	int length;
	int type;
	byte[] data;
	int crc;

	String typeString;

	public PNGChunk(int length, int type, byte[] data, int crc) {
	    this.length = length;
	    this.type = type;
	    this.data = data;
	    this.crc = crc;

	    typeString = new String();
	    typeString += (char)(type >> 24);
	    typeString += (char)((type >> 16) & 0xff);
	    typeString += (char)((type >> 8) & 0xff);
	    typeString += (char)(type & 0xff);
	}

	public int getLength() {
	    return length;
	}

	public int getType() {
	    return type;
	}

	public String getTypeString() {
	    return typeString;
	}

	public byte[] getData() {
	    return data;
	}

	public byte getByte(int offset) {
	    return data[offset];
	}

	public int getInt1(int offset) {
	    return data[offset] & 0xff;
	}

	public int getInt2(int offset) {
	    return ((data[offset] & 0xff) << 8) |
		(data[offset + 1] & 0xff);
	}

	public int getInt4(int offset) {
	    return ((data[offset] & 0xff) << 24) |
		((data[offset + 1] & 0xff) << 16) |
		((data[offset + 2] & 0xff) << 8) |
		(data[offset + 3] & 0xff);
	}

	public String getString4(int offset) {
	    String s = new String();
	    s += (char)data[offset];
	    s += (char)data[offset + 1];
	    s += (char)data[offset + 2];
	    s += (char)data[offset + 3];
	    return s;
	}

	public boolean isType(String typeName) {
	    return typeString.equals(typeName);
	}
    }

    public static final int PNG_COLOR_GRAY = 0;
    public static final int PNG_COLOR_RGB = 2;
    public static final int PNG_COLOR_PALETTE = 3;
    public static final int PNG_COLOR_GRAY_ALPHA = 4;
    public static final int PNG_COLOR_RGB_ALPHA = 6;

    private static final String[] colorTypeNames = {
        "Grayscale", "Error", "Truecolor", "Index",
        "Grayscale with alpha", "Error", "Truecolor with alpha"
    };

    public static final int PNG_FILTER_NONE = 0;
    public static final int PNG_FILTER_SUB = 1;
    public static final int PNG_FILTER_UP = 2;
    public static final int PNG_FILTER_AVERAGE = 3;
    public static final int PNG_FILTER_PAETH = 4;

    private static final int RED_OFFSET = 2;
    private static final int GREEN_OFFSET = 1;
    private static final int BLUE_OFFSET = 0;

    private int[][] bandOffsets = {
        null,
        { 0 }, // G
        { 0, 1 }, // GA in GA order
        { 0, 1, 2 }, // RGB in RGB order
        { 0, 1, 2, 3 } // RGBA in RGBA order
    };

    private int bitDepth;
    private int colorType;

    private int compressionMethod;
    private int filterMethod;
    private int interlaceMethod;
    
    private int paletteEntries;
    private byte[] redPalette;
    private byte[] greenPalette;
    private byte[] bluePalette;
    private byte[] alphaPalette;

    private int bkgdRed;
    private int bkgdGreen;
    private int bkgdBlue;

    private int grayTransparentAlpha;
    private int redTransparentAlpha;
    private int greenTransparentAlpha;
    private int blueTransparentAlpha;

    private int maxOpacity;

    private int[] significantBits = null;

    private boolean hasBackground = false;

    // Parameter information

    // If true, the user wants destination alpha where applicable.
    private boolean suppressAlpha = false;

    // If true, perform palette lookup internally
    private boolean expandPalette = false;
    
    // If true, output < 8 bit gray images in 8 bit components format
    private boolean output8BitGray = false;

    // Create an alpha channel in the destination color model.
    private boolean outputHasAlphaPalette = false;

    // Perform gamma correction on the image
    private boolean performGammaCorrection = false;

    // Expand GA to GGGA for compatbility with Java2D
    private boolean expandGrayAlpha = false;

    // Produce an instance of PNGEncodeParam
    private boolean generateEncodeParam = false;

    // PNGDecodeParam controlling decode process
    private PNGDecodeParam decodeParam = null;

    // PNGEncodeParam to store file details in
    private PNGEncodeParam encodeParam = null;

    private boolean emitProperties = true;

    private float fileGamma = 45455/100000.0F;

    private float userExponent = 1.0F;

    private float displayExponent = 2.2F;

    private float[] chromaticity = null;

    private int sRGBRenderingIntent = -1;

    // Post-processing step implied by above parameters
    private int postProcess = POST_NONE;

    // Possible post-processing steps

    // Do nothing
    private static final int POST_NONE = 0;

    // Gamma correct only
    private static final int POST_GAMMA = 1;

    // Push gray values through grayLut to expand to 8 bits
    private static final int POST_GRAY_LUT = 2;

    // Push gray values through grayLut to expand to 8 bits, add alpha
    private static final int POST_GRAY_LUT_ADD_TRANS = 3;

    // Push palette value through R,G,B lookup tables
    private static final int POST_PALETTE_TO_RGB = 4;

    // Push palette value through R,G,B,A lookup tables
    private static final int POST_PALETTE_TO_RGBA = 5;

    // Add transparency to a given gray value (w/ optional gamma)
    private static final int POST_ADD_GRAY_TRANS = 6;

    // Add transparency to a given RGB value (w/ optional gamma)
    private static final int POST_ADD_RGB_TRANS = 7; 

    // Remove the alpha channel from a gray image (w/ optional gamma)
    private static final int POST_REMOVE_GRAY_TRANS = 8;

    // Remove the alpha channel from an RGB image (w/optional gamma)
    private static final int POST_REMOVE_RGB_TRANS = 9; 

    // Mask to add expansion of GA -> GGGA
    private static final int POST_EXP_MASK = 16;

    // Expand gray to G/G/G
    private static final int POST_GRAY_ALPHA_EXP =
        POST_NONE | POST_EXP_MASK;

    // Expand gray to G/G/G through a gamma lut
    private static final int POST_GAMMA_EXP =
        POST_GAMMA | POST_EXP_MASK;

    // Push gray values through grayLut to expand to 8 bits, expand, add alpha
    private static final int POST_GRAY_LUT_ADD_TRANS_EXP =
        POST_GRAY_LUT_ADD_TRANS | POST_EXP_MASK;

    // Add transparency to a given gray value, expand
    private static final int POST_ADD_GRAY_TRANS_EXP = 
        POST_ADD_GRAY_TRANS | POST_EXP_MASK;

    private Vector streamVec = new Vector();
    private DataInputStream dataStream;

    private int bytesPerPixel; // number of bytes per input pixel
    private int inputBands;
    private int outputBands;

    // Number of private chunks
    private int chunkIndex = 0;

    private Vector textKeys = new Vector();
    private Vector textStrings = new Vector();

    private Vector ztextKeys = new Vector();
    private Vector ztextStrings = new Vector();

    private WritableRaster theTile;
    private Rectangle bounds;
    /** A Hashtable containing the image properties. */
    private Hashtable properties = new Hashtable();


    private int[] gammaLut = null;

    private void initGammaLut(int bits) {
        double exp = (double)userExponent/(fileGamma*displayExponent);
        int numSamples = 1 << bits;
        int maxOutSample = (bits == 16) ? 65535 : 255;

        gammaLut = new int[numSamples];
        for (int i = 0; i < numSamples; i++) {
            double gbright = (double)i/(numSamples - 1);
            double gamma = Math.pow(gbright, exp);
            int igamma = (int)(gamma*maxOutSample + 0.5);
            if (igamma > maxOutSample) {
                igamma = maxOutSample;
            }
            gammaLut[i] = igamma;
        }
    }

    private final byte[][] expandBits = {
        null,
        { (byte)0x00, (byte)0xff },
        { (byte)0x00, (byte)0x55, (byte)0xaa, (byte)0xff },
        null,
        { (byte)0x00, (byte)0x11, (byte)0x22, (byte)0x33,
          (byte)0x44, (byte)0x55, (byte)0x66, (byte)0x77,
          (byte)0x88, (byte)0x99, (byte)0xaa, (byte)0xbb,
          (byte)0xcc, (byte)0xdd, (byte)0xee, (byte)0xff }
    };

    private int[] grayLut = null;

    private void initGrayLut(int bits) {
        int len = 1 << bits;
        grayLut = new int[len];

        if (performGammaCorrection) {
            for (int i = 0; i < len; i++) {
                grayLut[i] = gammaLut[i];
            }
        } else {
            for (int i = 0; i < len; i++) {
                grayLut[i] = expandBits[bits][i];
            }
        }
    }

    public PNGRed(InputStream stream) throws IOException {
	this(stream, null);
    }

    public PNGRed(InputStream stream, PNGDecodeParam decodeParam)
        throws IOException {

        if (!stream.markSupported()) {
            stream = new BufferedInputStream(stream);
        }
        DataInputStream distream = new DataInputStream(stream);

        if (decodeParam == null) {
            decodeParam = new PNGDecodeParam();
        }
        this.decodeParam = decodeParam;

        // Get parameter values
        this.suppressAlpha = decodeParam.getSuppressAlpha();
        this.expandPalette = decodeParam.getExpandPalette();
        this.output8BitGray = decodeParam.getOutput8BitGray();
        this.expandGrayAlpha = decodeParam.getExpandGrayAlpha();
        if (decodeParam.getPerformGammaCorrection()) {
            this.userExponent = decodeParam.getUserExponent();
            this.displayExponent = decodeParam.getDisplayExponent();
            performGammaCorrection = true;
            output8BitGray = true;
        }
        this.generateEncodeParam = decodeParam.getGenerateEncodeParam();
        
        if (emitProperties) {
            properties.put("file_type", "PNG v. 1.0");
        }

        try {
            long magic = distream.readLong();
            if (magic != 0x89504e470d0a1a0aL) {
                String msg = PropertyUtil.getString("PNGImageDecoder0");
                throw new RuntimeException(msg);
            }
        } catch (Exception e) {
            e.printStackTrace();
            String msg = PropertyUtil.getString("PNGImageDecoder1");
            throw new RuntimeException(msg);
        }
            
        do {
            try {
                PNGChunk chunk;
                
                String chunkType = getChunkType(distream);
                if (chunkType.equals("IHDR")) {
                    chunk = readChunk(distream);
                    parse_IHDR_chunk(chunk);
                } else if (chunkType.equals("PLTE")) {
                    chunk = readChunk(distream);
                    parse_PLTE_chunk(chunk);
                } else if (chunkType.equals("IDAT")) {
                    chunk = readChunk(distream);
                    streamVec.add(new ByteArrayInputStream(chunk.getData()));
                } else if (chunkType.equals("IEND")) {
                    chunk = readChunk(distream);
                    parse_IEND_chunk(chunk);
                    break; // fall through to the bottom
                } else if (chunkType.equals("bKGD")) {
                    chunk = readChunk(distream);
                    parse_bKGD_chunk(chunk);
                } else if (chunkType.equals("cHRM")) {
                    chunk = readChunk(distream);
                    parse_cHRM_chunk(chunk);
                } else if (chunkType.equals("gAMA")) {
                    chunk = readChunk(distream);
                    parse_gAMA_chunk(chunk);
                } else if (chunkType.equals("hIST")) {
                    chunk = readChunk(distream);
                    parse_hIST_chunk(chunk);
                } else if (chunkType.equals("iCCP")) {
                    chunk = readChunk(distream);
                    parse_iCCP_chunk(chunk);
                } else if (chunkType.equals("pHYs")) {
                    chunk = readChunk(distream);
                    parse_pHYs_chunk(chunk);
                } else if (chunkType.equals("sBIT")) {
                    chunk = readChunk(distream);
                    parse_sBIT_chunk(chunk);
                } else if (chunkType.equals("sRGB")) {
                    chunk = readChunk(distream);
                    parse_sRGB_chunk(chunk);
                } else if (chunkType.equals("tEXt")) {
                    chunk = readChunk(distream);
                    parse_tEXt_chunk(chunk);
                } else if (chunkType.equals("tIME")) {
                    chunk = readChunk(distream);
                    parse_tIME_chunk(chunk);
                } else if (chunkType.equals("tRNS")) {
                    chunk = readChunk(distream);
                    parse_tRNS_chunk(chunk);
                } else if (chunkType.equals("zTXt")) {
                    chunk = readChunk(distream);
                    parse_zTXt_chunk(chunk);
                } else {
                    chunk = readChunk(distream);
                    // Output the chunk data in raw form

                    String type = chunk.getTypeString();
                    byte[] data = chunk.getData();
                    if (encodeParam != null) {
                        encodeParam.addPrivateChunk(type, data);
                    }
                    if (emitProperties) {
                        String key = "chunk_" + chunkIndex++ + ":" + type;
                        properties.put(key.toLowerCase(), data);
                    }
                }
            } catch (Exception e) {
                e.printStackTrace();
                String msg = PropertyUtil.getString("PNGImageDecoder2");
                throw new RuntimeException(msg);
            }
        } while (true);

        // Final post-processing

        if (significantBits == null) {
            significantBits = new int[inputBands];
            for (int i = 0; i < inputBands; i++) {
                significantBits[i] = bitDepth;
            }

            if (emitProperties) {
                properties.put("significant_bits", significantBits);
            }
        }
    }

    private static String getChunkType(DataInputStream distream) {
        try {
            distream.mark(8);
            /* int length = */ distream.readInt();
            int type      =    distream.readInt();
            distream.reset();

            String typeString = new String();
            typeString += (char)(type >> 24);
            typeString += (char)((type >> 16) & 0xff);
            typeString += (char)((type >> 8) & 0xff);
            typeString += (char)(type & 0xff);
            return typeString;
        } catch (Exception e) {
            e.printStackTrace();
            return null;
        }
    }

    private static PNGChunk readChunk(DataInputStream distream) {
        try {
            int length = distream.readInt();
            int type = distream.readInt();
            byte[] data = new byte[length];
            distream.readFully(data);
            int crc = distream.readInt();
            
            return new PNGChunk(length, type, data, crc);
        } catch (Exception e) {
            e.printStackTrace();
            return null;
        }
    }

    private void parse_IHDR_chunk(PNGChunk chunk) {
        int width  = chunk.getInt4(0);
        int height = chunk.getInt4(4);

	bounds = new Rectangle(0, 0, width, height);

        bitDepth = chunk.getInt1(8);
        
        if ((bitDepth != 1) && (bitDepth != 2) && (bitDepth != 4) &&
            (bitDepth != 8) && (bitDepth != 16)) {
            // Error -- bad bit depth
            String msg = PropertyUtil.getString("PNGImageDecoder3");
            throw new RuntimeException(msg);
        }
        maxOpacity = (1 << bitDepth) - 1;

        colorType = chunk.getInt1(9);
        if ((colorType != PNG_COLOR_GRAY) &&
            (colorType != PNG_COLOR_RGB) &&
            (colorType != PNG_COLOR_PALETTE) &&
            (colorType != PNG_COLOR_GRAY_ALPHA) &&
            (colorType != PNG_COLOR_RGB_ALPHA)) {
            System.out.println(PropertyUtil.getString("PNGImageDecoder4"));
        }

        if ((colorType == PNG_COLOR_RGB) && (bitDepth < 8)) {
            // Error -- RGB images must have 8 or 16 bits
            String msg = PropertyUtil.getString("PNGImageDecoder5");
            throw new RuntimeException(msg);
        }

        if ((colorType == PNG_COLOR_PALETTE) && (bitDepth == 16)) {
            // Error -- palette images must have < 16 bits
            String msg = PropertyUtil.getString("PNGImageDecoder6");
            throw new RuntimeException(msg);
        }

        if ((colorType == PNG_COLOR_GRAY_ALPHA) && (bitDepth < 8)) {
            // Error -- gray/alpha images must have >= 8 bits
            String msg = PropertyUtil.getString("PNGImageDecoder7");
            throw new RuntimeException(msg);
        }

        if ((colorType == PNG_COLOR_RGB_ALPHA) && (bitDepth < 8)) {
            // Error -- RGB/alpha images must have >= 8 bits
            String msg = PropertyUtil.getString("PNGImageDecoder8");
            throw new RuntimeException(msg);
        }

        if (emitProperties) {
            properties.put("color_type", colorTypeNames[colorType]);
        }

        if (generateEncodeParam) {
            if (colorType == PNG_COLOR_PALETTE) {
                encodeParam = new PNGEncodeParam.Palette();
            } else if (colorType == PNG_COLOR_GRAY ||
                       colorType == PNG_COLOR_GRAY_ALPHA) {
                encodeParam = new PNGEncodeParam.Gray();
            } else {
                encodeParam = new PNGEncodeParam.RGB();
            }
            decodeParam.setEncodeParam(encodeParam);
        }

        if (encodeParam != null) {
            encodeParam.setBitDepth(bitDepth);
        }
        if (emitProperties) {
            properties.put("bit_depth", new Integer(bitDepth));
        }

        if (performGammaCorrection) {
            // Assume file gamma is 1/2.2 unless we get a gAMA chunk
            float gamma = (1.0F/2.2F)*(displayExponent/userExponent);
            if (encodeParam != null) {
                encodeParam.setGamma(gamma);
            }
            if (emitProperties) {
                properties.put("gamma", new Float(gamma));
            }
        }

        compressionMethod = chunk.getInt1(10); 
        if (compressionMethod != 0) {
            // Error -- only know about compression method 0
            String msg = PropertyUtil.getString("PNGImageDecoder9");
            throw new RuntimeException(msg);
        }

        filterMethod = chunk.getInt1(11);
        if (filterMethod != 0) {
            // Error -- only know about filter method 0
            String msg = PropertyUtil.getString("PNGImageDecoder10");
            throw new RuntimeException(msg);
        }

        interlaceMethod = chunk.getInt1(12);
        if (interlaceMethod == 0) {
            if (encodeParam != null) {
                encodeParam.setInterlacing(false);
            }
            if (emitProperties) {
                properties.put("interlace_method", "None");
            }
        } else if (interlaceMethod == 1) {
            if (encodeParam != null) {
                encodeParam.setInterlacing(true);
            }
            if (emitProperties) {
                properties.put("interlace_method", "Adam7");
            }
        } else {
            // Error -- only know about Adam7 interlacing
            String msg = PropertyUtil.getString("PNGImageDecoder11");
            throw new RuntimeException(msg);
        }
        
        bytesPerPixel = (bitDepth == 16) ? 2 : 1;

        switch (colorType) {
        case PNG_COLOR_GRAY:
            inputBands = 1;
            outputBands = 1;

            if (output8BitGray && (bitDepth < 8)) {
                postProcess = POST_GRAY_LUT;
            } else if (performGammaCorrection) {
                postProcess = POST_GAMMA;
            } else {
                postProcess = POST_NONE;
            }
            break;

        case PNG_COLOR_RGB:
            inputBands = 3;
            bytesPerPixel *= 3;
            outputBands = 3;

            if (performGammaCorrection) {
                postProcess = POST_GAMMA;
            } else {
                postProcess = POST_NONE;
            }
            break;

        case PNG_COLOR_PALETTE:
            inputBands = 1;
            bytesPerPixel = 1;
            outputBands = expandPalette ? 3 : 1;

            if (expandPalette) {
                postProcess = POST_PALETTE_TO_RGB;
            } else {
                postProcess = POST_NONE;
            }
            break;

        case PNG_COLOR_GRAY_ALPHA:
            inputBands = 2;
            bytesPerPixel *= 2;

            if (suppressAlpha) {
                outputBands = 1;
                postProcess = POST_REMOVE_GRAY_TRANS;
            } else {
                if (performGammaCorrection) {
                    postProcess = POST_GAMMA;
                } else {
                    postProcess = POST_NONE;
                }
                if (expandGrayAlpha) {
                    postProcess |= POST_EXP_MASK;
                    outputBands = 4;
                } else {
                    outputBands = 2;
                }
            }
            break;

        case PNG_COLOR_RGB_ALPHA:
            inputBands = 4;
            bytesPerPixel *= 4;
            outputBands = (!suppressAlpha) ? 4 : 3;

            if (suppressAlpha) {
                postProcess = POST_REMOVE_RGB_TRANS;
            } else if (performGammaCorrection) {
                postProcess = POST_GAMMA;
            } else {
                postProcess = POST_NONE;
            }
            break;
        }
    }

    private void parse_IEND_chunk(PNGChunk chunk) throws Exception {
        // Store text strings
        int textLen = textKeys.size();
        String[] textArray = new String[2*textLen];
        for (int i = 0; i < textLen; i++) {
            String key = (String)textKeys.elementAt(i);
            String val = (String)textStrings.elementAt(i);
            textArray[2*i] = key;
            textArray[2*i + 1] = val;
            if (emitProperties) {
                String uniqueKey = "text_" + i + ":" + key;
                properties.put(uniqueKey.toLowerCase(), val);
            }
        }
        if (encodeParam != null) {
            encodeParam.setText(textArray);
        }

        // Store compressed text strings
        int ztextLen = ztextKeys.size();
        String[] ztextArray = new String[2*ztextLen];
        for (int i = 0; i < ztextLen; i++) {
            String key = (String)ztextKeys.elementAt(i);
            String val = (String)ztextStrings.elementAt(i);
            ztextArray[2*i] = key;
            ztextArray[2*i + 1] = val;
            if (emitProperties) {
                String uniqueKey = "ztext_" + i + ":" + key;
                properties.put(uniqueKey.toLowerCase(), val);
            }
        }
        if (encodeParam != null) {
            encodeParam.setCompressedText(ztextArray);
        }

        // Parse prior IDAT chunks
        InputStream seqStream = 
            new SequenceInputStream(streamVec.elements());
        InputStream infStream =
            new InflaterInputStream(seqStream, new Inflater());
        dataStream = new DataInputStream(infStream);
        
        // Create an empty WritableRaster
        int depth = bitDepth;
        if ((colorType == PNG_COLOR_GRAY) && 
            (bitDepth < 8) && output8BitGray) {
            depth = 8;
        }
        if ((colorType == PNG_COLOR_PALETTE) && expandPalette) {
            depth = 8;
        }
	int width  = bounds.width;
	int height = bounds.height;

        int bytesPerRow = (outputBands*width*depth + 7)/8;
        int scanlineStride =
            (depth == 16) ? (bytesPerRow/2) : bytesPerRow;

        theTile = createRaster(width, height, outputBands,
                               scanlineStride,
                               depth);

        if (performGammaCorrection && (gammaLut == null)) {
            initGammaLut(bitDepth);
        }
        if ((postProcess == POST_GRAY_LUT) ||
            (postProcess == POST_GRAY_LUT_ADD_TRANS) ||
            (postProcess == POST_GRAY_LUT_ADD_TRANS_EXP)) {
            initGrayLut(bitDepth);
        }

        decodeImage(interlaceMethod == 1);
        SampleModel sm = theTile.getSampleModel();
	ColorModel  cm;

        if ((colorType == PNG_COLOR_PALETTE) && !expandPalette) {
            if (outputHasAlphaPalette) {
                cm = new IndexColorModel(bitDepth,
                                                 paletteEntries,
                                                 redPalette,
                                                 greenPalette,
                                                 bluePalette,
                                                 alphaPalette);
            } else {
                cm = new IndexColorModel(bitDepth,
                                                 paletteEntries,
                                                 redPalette,
                                                 greenPalette,
                                                 bluePalette);
            }
        } else if ((colorType == PNG_COLOR_GRAY) && 
                   (bitDepth < 8) && !output8BitGray) {
            byte[] palette = expandBits[bitDepth];
            cm = new IndexColorModel(bitDepth,
                                             palette.length,
                                             palette,
                                             palette,
                                             palette);
        } else {
            cm =
                createComponentColorModel(sm);
        }

	init((CachableRed)null, bounds, cm, sm, 0, 0, properties);
    }

    private static final int[] GrayBits8 = { 8 };
    private static final ComponentColorModel colorModelGray8 =
        new ComponentColorModel(ColorSpace.getInstance(ColorSpace.CS_GRAY),
                                GrayBits8, false, false,
                                Transparency.OPAQUE,
                                DataBuffer.TYPE_BYTE);

    private static final int[] GrayAlphaBits8 = { 8, 8 };
    private static final ComponentColorModel colorModelGrayAlpha8 =
        new ComponentColorModel(ColorSpace.getInstance(ColorSpace.CS_GRAY),
                                GrayAlphaBits8, true, false,
                                Transparency.TRANSLUCENT,
                                DataBuffer.TYPE_BYTE);

    private static final int[] GrayBits16 = { 16 };
    private static final ComponentColorModel colorModelGray16 =
        new ComponentColorModel(ColorSpace.getInstance(ColorSpace.CS_GRAY),
                                GrayBits16, false, false,
                                Transparency.OPAQUE,
                                DataBuffer.TYPE_USHORT);

    private static final int[] GrayAlphaBits16 = { 16, 16 };
    private static final ComponentColorModel colorModelGrayAlpha16 =
        new ComponentColorModel(ColorSpace.getInstance(ColorSpace.CS_GRAY),
                                GrayAlphaBits16, true, false,
                                Transparency.TRANSLUCENT,
                                DataBuffer.TYPE_USHORT);

    private static final int[] GrayBits32 = { 32 };
    private static final ComponentColorModel colorModelGray32 =
        new ComponentColorModel(ColorSpace.getInstance(ColorSpace.CS_GRAY),
                                GrayBits32, false, false,
                                Transparency.OPAQUE,
                                DataBuffer.TYPE_INT);

    private static final int[] GrayAlphaBits32 = { 32, 32 };
    private static final ComponentColorModel colorModelGrayAlpha32 =
        new ComponentColorModel(ColorSpace.getInstance(ColorSpace.CS_GRAY),
                                GrayAlphaBits32, true, false,
                                Transparency.TRANSLUCENT,
                                DataBuffer.TYPE_INT);

    private static final int[] RGBBits8 = { 8, 8, 8 };
    private static final ComponentColorModel colorModelRGB8 =
      new ComponentColorModel(ColorSpace.getInstance(ColorSpace.CS_sRGB),
                              RGBBits8, false, false,
                              Transparency.OPAQUE,
                              DataBuffer.TYPE_BYTE);

    private static final int[] RGBABits8 = { 8, 8, 8, 8 };
    private static final ComponentColorModel colorModelRGBA8 =
      new ComponentColorModel(ColorSpace.getInstance(ColorSpace.CS_sRGB),
                              RGBABits8, true, false,
                              Transparency.TRANSLUCENT,
                              DataBuffer.TYPE_BYTE);

    private static final int[] RGBBits16 = { 16, 16, 16 };
    private static final ComponentColorModel colorModelRGB16 =
      new ComponentColorModel(ColorSpace.getInstance(ColorSpace.CS_sRGB),
                              RGBBits16, false, false,
                              Transparency.OPAQUE,
                              DataBuffer.TYPE_USHORT);

    private static final int[] RGBABits16 = { 16, 16, 16, 16 };
    private static final ComponentColorModel colorModelRGBA16 =
      new ComponentColorModel(ColorSpace.getInstance(ColorSpace.CS_sRGB),
                              RGBABits16, true, false,
                              Transparency.TRANSLUCENT,
                              DataBuffer.TYPE_USHORT);

    private static final int[] RGBBits32 = { 32, 32, 32 };
    private static final ComponentColorModel colorModelRGB32 =
      new ComponentColorModel(ColorSpace.getInstance(ColorSpace.CS_sRGB),
                              RGBBits32, false, false,
                              Transparency.OPAQUE,
                              DataBuffer.TYPE_INT);

    private static final int[] RGBABits32 = { 32, 32, 32, 32 };
    private static final ComponentColorModel colorModelRGBA32 =
      new ComponentColorModel(ColorSpace.getInstance(ColorSpace.CS_sRGB),
                              RGBABits32, true, false,
                              Transparency.TRANSLUCENT,
                              DataBuffer.TYPE_INT);
    /**
     * A convenience method to create an instance of
     * <code>ComponentColorModel</code> suitable for use with the
     * given <code>SampleModel</code>.  The <code>SampleModel</code>
     * should have a data type of <code>DataBuffer.TYPE_BYTE</code>,
     * <code>TYPE_USHORT</code>, or <code>TYPE_INT</code> and between
     * 1 and 4 bands.  Depending on the number of bands of the
     * <code>SampleModel</code>, either a gray, gray+alpha, rgb, or
     * rgb+alpha <code>ColorModel</code> is returned.
     */
    public static ColorModel createComponentColorModel(SampleModel sm) {
        int type = sm.getDataType();
        int bands = sm.getNumBands();
        ComponentColorModel cm = null;

        if (type == DataBuffer.TYPE_BYTE) {
            switch (bands) {
            case 1:
                cm = colorModelGray8;
                break;
            case 2:
                cm = colorModelGrayAlpha8;
                break;
            case 3:
                cm = colorModelRGB8;
                break;
            case 4:
                cm = colorModelRGBA8;
                break;
            }
        } else if (type == DataBuffer.TYPE_USHORT) {
            switch (bands) {
            case 1:
                cm = colorModelGray16;
                break;
            case 2:
                cm = colorModelGrayAlpha16;
                break;
            case 3:
                cm = colorModelRGB16;
                break;
            case 4:
                cm = colorModelRGBA16;
                break;
            }
        } else if (type == DataBuffer.TYPE_INT) {
            switch (bands) {
            case 1:
                cm = colorModelGray32;
                break;
            case 2:
                cm = colorModelGrayAlpha32;
                break;
            case 3:
                cm = colorModelRGB32;
                break;
            case 4:
                cm = colorModelRGBA32;
                break;
            }
        }

        return cm;
    }

    private void parse_PLTE_chunk(PNGChunk chunk) {
        paletteEntries = chunk.getLength()/3;
        redPalette = new byte[paletteEntries];
        greenPalette = new byte[paletteEntries];
        bluePalette = new byte[paletteEntries];

        int pltIndex = 0;

        // gAMA chunk must precede PLTE chunk 
        if (performGammaCorrection) {
            if (gammaLut == null) {
                initGammaLut(bitDepth == 16 ? 16 : 8);
            }
            
            for (int i = 0; i < paletteEntries; i++) {
                byte r = chunk.getByte(pltIndex++);
                byte g = chunk.getByte(pltIndex++);
                byte b = chunk.getByte(pltIndex++);

                redPalette[i] = (byte)gammaLut[r & 0xff];
                greenPalette[i] = (byte)gammaLut[g & 0xff];
                bluePalette[i] = (byte)gammaLut[b & 0xff];
            }
        } else {
            for (int i = 0; i < paletteEntries; i++) {
                redPalette[i] = chunk.getByte(pltIndex++);
                greenPalette[i] = chunk.getByte(pltIndex++);
                bluePalette[i] = chunk.getByte(pltIndex++);
            }
        }
    }

    private void parse_bKGD_chunk(PNGChunk chunk) {
        hasBackground = true;

        switch (colorType) {
        case PNG_COLOR_PALETTE:
            int bkgdIndex = chunk.getByte(0) & 0xff;

            bkgdRed = redPalette[bkgdIndex] & 0xff;
            bkgdGreen = greenPalette[bkgdIndex] & 0xff;
            bkgdBlue = bluePalette[bkgdIndex] & 0xff;

            if (encodeParam != null) {
                ((PNGEncodeParam.Palette)encodeParam).
                    setBackgroundPaletteIndex(bkgdIndex);
            }
            break;
        case PNG_COLOR_GRAY: case PNG_COLOR_GRAY_ALPHA:
            int bkgdGray = chunk.getInt2(0);
            bkgdRed = bkgdGreen = bkgdBlue = bkgdGray;

            if (encodeParam != null) {
                ((PNGEncodeParam.Gray)encodeParam).
                    setBackgroundGray(bkgdGray);
            }
            break;
        case PNG_COLOR_RGB: case PNG_COLOR_RGB_ALPHA:
            bkgdRed = chunk.getInt2(0);
            bkgdGreen = chunk.getInt2(2);
            bkgdBlue = chunk.getInt2(4);

            int[] bkgdRGB = new int[3];
            bkgdRGB[0] = bkgdRed;
            bkgdRGB[1] = bkgdGreen;
            bkgdRGB[2] = bkgdBlue;
            if (encodeParam != null) {
                ((PNGEncodeParam.RGB)encodeParam).
                    setBackgroundRGB(bkgdRGB);
            }
            break;
        }

        int r = 0, g = 0, b = 0;
        if ((colorType == PNG_COLOR_PALETTE) || (bitDepth == 8)) {
            r = bkgdRed;
            g = bkgdGreen;
            b = bkgdBlue;
        } else if (bitDepth < 8) {
            r = expandBits[bitDepth][bkgdRed];
            g = expandBits[bitDepth][bkgdGreen];
            b = expandBits[bitDepth][bkgdBlue];
        } else if (bitDepth == 16) {
            r = bkgdRed >> 8;
            g = bkgdGreen >> 8;
            b = bkgdBlue >> 8;
        }
        if (emitProperties) {
            properties.put("background_color", new Color(r, g, b));
        }
    }

    private void parse_cHRM_chunk(PNGChunk chunk) {
        // If an sRGB chunk exists, ignore cHRM chunks
        if (sRGBRenderingIntent != -1) {
            return;
        }

        chromaticity = new float[8];
        chromaticity[0] = chunk.getInt4(0)/100000.0F;
        chromaticity[1] = chunk.getInt4(4)/100000.0F;
        chromaticity[2] = chunk.getInt4(8)/100000.0F;
        chromaticity[3] = chunk.getInt4(12)/100000.0F;
        chromaticity[4] = chunk.getInt4(16)/100000.0F;
        chromaticity[5] = chunk.getInt4(20)/100000.0F;
        chromaticity[6] = chunk.getInt4(24)/100000.0F;
        chromaticity[7] = chunk.getInt4(28)/100000.0F;

        if (encodeParam != null) {
            encodeParam.setChromaticity(chromaticity);
        }
        if (emitProperties) {
            properties.put("white_point_x", new Float(chromaticity[0]));
            properties.put("white_point_y", new Float(chromaticity[1]));
            properties.put("red_x", new Float(chromaticity[2]));
            properties.put("red_y", new Float(chromaticity[3]));
            properties.put("green_x", new Float(chromaticity[4]));
            properties.put("green_y", new Float(chromaticity[5]));
            properties.put("blue_x", new Float(chromaticity[6]));
            properties.put("blue_y", new Float(chromaticity[7]));
        }
    }

    private void parse_gAMA_chunk(PNGChunk chunk) {
        // If an sRGB chunk exists, ignore gAMA chunks
        if (sRGBRenderingIntent != -1) {
            return;
        }

        fileGamma = chunk.getInt4(0)/100000.0F;
        // System.out.println("Gamma: " + fileGamma);
        float exp =
            performGammaCorrection ? displayExponent/userExponent : 1.0F;
        if (encodeParam != null) {
            encodeParam.setGamma(fileGamma*exp);
        }
        if (emitProperties) {
            properties.put("gamma", new Float(fileGamma*exp));
        }
    }
    
    private void parse_hIST_chunk(PNGChunk chunk) {
        if (redPalette == null) {
            String msg = PropertyUtil.getString("PNGImageDecoder18");
            throw new RuntimeException(msg);
        }

        int length = redPalette.length;
        int[] hist = new int[length];
        for (int i = 0; i < length; i++) {
            hist[i] = chunk.getInt2(2*i);
        }
        
        if (encodeParam != null) {
            encodeParam.setPaletteHistogram(hist);
        }
    }

    private void parse_iCCP_chunk(PNGChunk chunk) {
        String name = new String();
        byte b;

        int textIndex = 0;
        while ((b = chunk.getByte(textIndex++)) != 0) {
            name += (char)b;
        }
    }

    private void parse_pHYs_chunk(PNGChunk chunk) {
        int xPixelsPerUnit = chunk.getInt4(0);
        int yPixelsPerUnit = chunk.getInt4(4);
        int unitSpecifier = chunk.getInt1(8);

        if (encodeParam != null) {
            encodeParam.setPhysicalDimension(xPixelsPerUnit,
                                             yPixelsPerUnit,
                                             unitSpecifier);
        }
        if (emitProperties) {
            properties.put("x_pixels_per_unit", new Integer(xPixelsPerUnit));
            properties.put("y_pixels_per_unit", new Integer(yPixelsPerUnit));
            properties.put("pixel_aspect_ratio", 
                           new Float((float)xPixelsPerUnit/yPixelsPerUnit));
            if (unitSpecifier == 1) {
                properties.put("pixel_units", "Meters");
            } else if (unitSpecifier != 0) {
                // Error -- unit specifier must be 0 or 1
                String msg = PropertyUtil.getString("PNGImageDecoder12");
                throw new RuntimeException(msg);
            }
        }
    }

    private void parse_sBIT_chunk(PNGChunk chunk) {
        if (colorType == PNG_COLOR_PALETTE) {
            significantBits = new int[3];
        } else {
            significantBits = new int[inputBands];
        }
        for (int i = 0; i < significantBits.length; i++) {
            int bits = chunk.getByte(i);
            int depth = (colorType == PNG_COLOR_PALETTE) ? 8 : bitDepth;
            if (bits <= 0 || bits > depth) {
                // Error -- significant bits must be between 0 and
                // image bit depth.
                String msg = PropertyUtil.getString("PNGImageDecoder13");
                throw new RuntimeException(msg);
            }
            significantBits[i] = bits;
        }

        if (encodeParam != null) {
            encodeParam.setSignificantBits(significantBits);
        }
        if (emitProperties) {
            properties.put("significant_bits", significantBits);
        }
    }

    private void parse_sRGB_chunk(PNGChunk chunk) {
        sRGBRenderingIntent = chunk.getByte(0);

        // The presence of an sRGB chunk implies particular
        // settings for gamma and chroma.
        fileGamma = 45455/100000.0F;

        chromaticity = new float[8];
        chromaticity[0] = 31270/10000.0F;
        chromaticity[1] = 32900/10000.0F;
        chromaticity[2] = 64000/10000.0F;
        chromaticity[3] = 33000/10000.0F;
        chromaticity[4] = 30000/10000.0F;
        chromaticity[5] = 60000/10000.0F;
        chromaticity[6] = 15000/10000.0F;
        chromaticity[7] =  6000/10000.0F;

        if (performGammaCorrection) {
            // File gamma is 1/2.2
            float gamma = fileGamma*(displayExponent/userExponent);
            if (encodeParam != null) {
                encodeParam.setGamma(gamma);
                encodeParam.setChromaticity(chromaticity);
            }
            if (emitProperties) {
                properties.put("gamma", new Float(gamma));
                properties.put("white_point_x", new Float(chromaticity[0]));
                properties.put("white_point_y", new Float(chromaticity[1]));
                properties.put("red_x", new Float(chromaticity[2]));
                properties.put("red_y", new Float(chromaticity[3]));
                properties.put("green_x", new Float(chromaticity[4]));
                properties.put("green_y", new Float(chromaticity[5]));
                properties.put("blue_x", new Float(chromaticity[6]));
                properties.put("blue_y", new Float(chromaticity[7]));
            }
        }
    }

    private void parse_tEXt_chunk(PNGChunk chunk) {
        String key = new String();
        String value = new String();
        byte b;
        
        int textIndex = 0;
        while ((b = chunk.getByte(textIndex++)) != 0) {
            key += (char)b;
        }

        for (int i = textIndex; i < chunk.getLength(); i++) {
            value += (char)chunk.getByte(i);
        }

        textKeys.add(key);
        textStrings.add(value);
    }

    private void parse_tIME_chunk(PNGChunk chunk) {
        int year = chunk.getInt2(0);
        int month = chunk.getInt1(2) - 1;
        int day = chunk.getInt1(3);
        int hour = chunk.getInt1(4);
        int minute = chunk.getInt1(5);
        int second = chunk.getInt1(6);
        
        TimeZone gmt = TimeZone.getTimeZone("GMT");
        
        GregorianCalendar cal = new GregorianCalendar(gmt);
        cal.set(year, month, day,
                hour, minute, second);
        Date date = cal.getTime();
        
        if (encodeParam != null) {
            encodeParam.setModificationTime(date);
        }
        if (emitProperties) {
            properties.put("timestamp", date);
        }
    }

    private void parse_tRNS_chunk(PNGChunk chunk) {
        if (colorType == PNG_COLOR_PALETTE) {
            int entries = chunk.getLength();
            if (entries > paletteEntries) {
                // Error -- mustn't have more alpha than RGB palette entries
                String msg = PropertyUtil.getString("PNGImageDecoder14");
                throw new RuntimeException(msg);
            }

            // Load beginning of palette from the chunk
            alphaPalette = new byte[paletteEntries];
            for (int i = 0; i < entries; i++) {
                alphaPalette[i] = chunk.getByte(i);
            }
            
            // Fill rest of palette with 255
            for (int i = entries; i < paletteEntries; i++) {
                alphaPalette[i] = (byte)255;
            }

            if (!suppressAlpha) {
                if (expandPalette) {
                    postProcess = POST_PALETTE_TO_RGBA;
                    outputBands = 4;
                } else {
                    outputHasAlphaPalette = true;
                }
            }
        } else if (colorType == PNG_COLOR_GRAY) {
            grayTransparentAlpha = chunk.getInt2(0);
            
            if (!suppressAlpha) {
                if (bitDepth < 8) {
                    output8BitGray = true;
                    maxOpacity = 255;
                    postProcess = POST_GRAY_LUT_ADD_TRANS;
                } else {
                    postProcess = POST_ADD_GRAY_TRANS;
                }

                if (expandGrayAlpha) {
                    outputBands = 4;
                    postProcess |= POST_EXP_MASK;
                } else {
                    outputBands = 2;
                }
                
                if (encodeParam != null) {
                    ((PNGEncodeParam.Gray)encodeParam).
                        setTransparentGray(grayTransparentAlpha);
                }
            }
        } else if (colorType == PNG_COLOR_RGB) {
            redTransparentAlpha = chunk.getInt2(0);
            greenTransparentAlpha = chunk.getInt2(2);
            blueTransparentAlpha = chunk.getInt2(4);

            if (!suppressAlpha) {
                outputBands = 4;
                postProcess = POST_ADD_RGB_TRANS;
                
                if (encodeParam != null) {
                    int[] rgbTrans = new int[3];
                    rgbTrans[0] = redTransparentAlpha;
                    rgbTrans[1] = greenTransparentAlpha;
                    rgbTrans[2] = blueTransparentAlpha;
                    ((PNGEncodeParam.RGB)encodeParam).
                        setTransparentRGB(rgbTrans);
                }
            }
        } else if (colorType == PNG_COLOR_GRAY_ALPHA ||
                   colorType == PNG_COLOR_RGB_ALPHA) {
            // Error -- GA or RGBA image can't have a tRNS chunk.
            String msg = PropertyUtil.getString("PNGImageDecoder15");
            throw new RuntimeException(msg);
        }
    }

    private void parse_zTXt_chunk(PNGChunk chunk) {
        String key = new String();
        String value = new String();
        byte b;
        
        int textIndex = 0;
        while ((b = chunk.getByte(textIndex++)) != 0) {
            key += (char)b;
        }
        /* int method = */ chunk.getByte(textIndex++);

        try {
            int length = chunk.getLength() - textIndex;
            byte[] data = chunk.getData();
            InputStream cis =
                new ByteArrayInputStream(data, textIndex, length);
            InputStream iis = new InflaterInputStream(cis);
            
            int c;
            while ((c = iis.read()) != -1) {
                value += (char)c;
            }
            
            ztextKeys.add(key);
            ztextStrings.add(value);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    private WritableRaster createRaster(int width, int height, int bands,
                                        int scanlineStride,
                                        int bitDepth) {

        DataBuffer dataBuffer;
        WritableRaster ras = null;
        Point origin = new Point(0, 0);
        if ((bitDepth < 8) && (bands == 1)) {
            dataBuffer = new DataBufferByte(height*scanlineStride);
            ras = Raster.createPackedRaster(dataBuffer,
                                            width, height,
                                            bitDepth,
                                            origin);
        } else if (bitDepth <= 8) {
            dataBuffer = new DataBufferByte(height*scanlineStride);
           ras = Raster.createInterleavedRaster(dataBuffer,
                                                 width, height,
                                                 scanlineStride,
                                                 bands,
                                                 bandOffsets[bands],
                                                 origin);
        } else {
            dataBuffer = new DataBufferUShort(height*scanlineStride);
            ras = Raster.createInterleavedRaster(dataBuffer,
                                                 width, height,
                                                 scanlineStride,
                                                 bands,
                                                 bandOffsets[bands],
                                                 origin);
        }

        return ras;
    }

    // Data filtering methods

    private static void decodeSubFilter(byte[] curr, int count, int bpp) {
        for (int i = bpp; i < count; i++) {
            int val;

            val = curr[i] & 0xff;
            val += curr[i - bpp] & 0xff;

            curr[i] = (byte)val;
        }
    }

    private static void decodeUpFilter(byte[] curr, byte[] prev,
                                       int count) {
        for (int i = 0; i < count; i++) {
            int raw = curr[i] & 0xff;
            int prior = prev[i] & 0xff;

            curr[i] = (byte)(raw + prior);
        }
    }

    private static void decodeAverageFilter(byte[] curr, byte[] prev,
                                            int count, int bpp) {
        int raw, priorPixel, priorRow;

        for (int i = 0; i < bpp; i++) {
            raw = curr[i] & 0xff;
            priorRow = prev[i] & 0xff;
            
            curr[i] = (byte)(raw + priorRow/2);
        }

        for (int i = bpp; i < count; i++) {
            raw = curr[i] & 0xff;
            priorPixel = curr[i - bpp] & 0xff;
            priorRow = prev[i] & 0xff;
            
            curr[i] = (byte)(raw + (priorPixel + priorRow)/2);
        }
    }

    private static int paethPredictor(int a, int b, int c) {
        int p = a + b - c;
        int pa = Math.abs(p - a);
        int pb = Math.abs(p - b);
        int pc = Math.abs(p - c);

        if ((pa <= pb) && (pa <= pc)) {
            return a;
        } else if (pb <= pc) {
            return b;
        } else {
            return c;
        }
    } 

    private static void decodePaethFilter(byte[] curr, byte[] prev,
                                          int count, int bpp) {
        int raw, priorPixel, priorRow, priorRowPixel;

        for (int i = 0; i < bpp; i++) {
            raw = curr[i] & 0xff;
            priorRow = prev[i] & 0xff;

            curr[i] = (byte)(raw + priorRow);
        }

        for (int i = bpp; i < count; i++) {
            raw = curr[i] & 0xff;
            priorPixel = curr[i - bpp] & 0xff;
            priorRow = prev[i] & 0xff;
            priorRowPixel = prev[i - bpp] & 0xff;

            curr[i] = (byte)(raw + paethPredictor(priorPixel,
                                                  priorRow,
                                                  priorRowPixel));
        }
    }

    private void processPixels(int process,
                               Raster src, WritableRaster dst,
                               int xOffset, int step, int y, int width) {
        int srcX, dstX;

        // Create an array suitable for holding one pixel
        int[] ps = src.getPixel(0, 0, (int[])null);
        int[] pd = dst.getPixel(0, 0, (int[])null);

        dstX = xOffset;
        switch (process) {
        case POST_NONE:
            for (srcX = 0; srcX < width; srcX++) {
                src.getPixel(srcX, 0, ps);
                dst.setPixel(dstX, y, ps);
                dstX += step;
            }
            break;

        case POST_GAMMA:
            for (srcX = 0; srcX < width; srcX++) {
                src.getPixel(srcX, 0, ps);
                    
                for (int i = 0; i < inputBands; i++) {
                    int x = ps[i];
                    ps[i] = gammaLut[x];
                }
                    
                dst.setPixel(dstX, y, ps);
                dstX += step;
            }
            break;

        case POST_GRAY_LUT:
            for (srcX = 0; srcX < width; srcX++) {
                src.getPixel(srcX, 0, ps);

                pd[0] = grayLut[ps[0]];

                dst.setPixel(dstX, y, pd);
                dstX += step;
            }
            break;

        case POST_GRAY_LUT_ADD_TRANS:
            for (srcX = 0; srcX < width; srcX++) {
                src.getPixel(srcX, 0, ps);

                int val = ps[0];
                pd[0] = grayLut[val];
                if (val == grayTransparentAlpha) {
                    pd[1] = 0;
                } else {
                    pd[1] = maxOpacity;
                }
                
                dst.setPixel(dstX, y, pd);
                dstX += step;
            }
            break;

        case POST_PALETTE_TO_RGB:
            for (srcX = 0; srcX < width; srcX++) {
                src.getPixel(srcX, 0, ps);
                
                int val = ps[0];
                pd[0] = redPalette[val];
                pd[1] = greenPalette[val];
                pd[2] = bluePalette[val];
                
                dst.setPixel(dstX, y, pd);
                dstX += step;
            }
            break;

        case POST_PALETTE_TO_RGBA:
            for (srcX = 0; srcX < width; srcX++) {
                src.getPixel(srcX, 0, ps);

                int val = ps[0];
                pd[0] = redPalette[val];
                pd[1] = greenPalette[val];
                pd[2] = bluePalette[val];
                pd[3] = alphaPalette[val];

                dst.setPixel(dstX, y, pd);
                dstX += step;
            }
            break;

        case POST_ADD_GRAY_TRANS:
            for (srcX = 0; srcX < width; srcX++) {
                src.getPixel(srcX, 0, ps);

                int val = ps[0];
                if (performGammaCorrection) {
                    val = gammaLut[val];
                }
                pd[0] = val;
                if (val == grayTransparentAlpha) {
                    pd[1] = 0;
                } else {
                    pd[1] = maxOpacity;
                }

                dst.setPixel(dstX, y, pd);
                dstX += step;
            }
            break;

        case POST_ADD_RGB_TRANS:
            for (srcX = 0; srcX < width; srcX++) {
                src.getPixel(srcX, 0, ps);

                int r = ps[0];
                int g = ps[1];
                int b = ps[2];
                if (performGammaCorrection) {
                    pd[0] = gammaLut[r];
                    pd[1] = gammaLut[g];
                    pd[2] = gammaLut[b];
                } else {
                    pd[0] = r;
                    pd[1] = g;
                    pd[2] = b;
                }
                if ((r == redTransparentAlpha) &&
                    (g == greenTransparentAlpha) &&
                    (b == blueTransparentAlpha)) {
                    pd[3] = 0;
                } else {
                    pd[3] = maxOpacity;
                }

                dst.setPixel(dstX, y, pd);
                dstX += step;
            }
            break;

        case POST_REMOVE_GRAY_TRANS:
            for (srcX = 0; srcX < width; srcX++) {
                src.getPixel(srcX, 0, ps);

                int g = ps[0];
                if (performGammaCorrection) {
                    pd[0] = gammaLut[g];
                } else {
                    pd[0] = g;
                }

                dst.setPixel(dstX, y, pd);
                dstX += step;
            }
            break;

        case POST_REMOVE_RGB_TRANS:
            for (srcX = 0; srcX < width; srcX++) {
                src.getPixel(srcX, 0, ps);

                int r = ps[0];
                int g = ps[1];
                int b = ps[2];
                if (performGammaCorrection) {
                    pd[0] = gammaLut[r];
                    pd[1] = gammaLut[g];
                    pd[2] = gammaLut[b];
                } else {
                    pd[0] = r;
                    pd[1] = g;
                    pd[2] = b;
                }

                dst.setPixel(dstX, y, pd);
                dstX += step;
            }
            break;

        case POST_GAMMA_EXP:
            for (srcX = 0; srcX < width; srcX++) {
                src.getPixel(srcX, 0, ps);
                    
                int val = ps[0];
                int alpha = ps[1];
                int gamma = gammaLut[val];
                pd[0] = gamma;
                pd[1] = gamma;
                pd[2] = gamma;
                pd[3] = alpha;
                    
                dst.setPixel(dstX, y, pd);
                dstX += step;
            }
            break;

        case POST_GRAY_ALPHA_EXP:
            for (srcX = 0; srcX < width; srcX++) {
                src.getPixel(srcX, 0, ps);
                    
                int val = ps[0];
                int alpha = ps[1];
                pd[0] = val;
                pd[1] = val;
                pd[2] = val;
                pd[3] = alpha;
                    
                dst.setPixel(dstX, y, pd);
                dstX += step;
            }
            break;

        case POST_ADD_GRAY_TRANS_EXP:
            for (srcX = 0; srcX < width; srcX++) {
                src.getPixel(srcX, 0, ps);

                int val = ps[0];
                if (performGammaCorrection) {
                    val = gammaLut[val];
                }
                pd[0] = val;
                pd[1] = val;
                pd[2] = val;
                if (val == grayTransparentAlpha) {
                    pd[3] = 0;
                } else {
                    pd[3] = maxOpacity;
                }

                dst.setPixel(dstX, y, pd);
                dstX += step;
            }
            break;

        case POST_GRAY_LUT_ADD_TRANS_EXP:
            for (srcX = 0; srcX < width; srcX++) {
                src.getPixel(srcX, 0, ps);

                int val = ps[0];
                int val2 = grayLut[val];
                pd[0] = val2;
                pd[1] = val2;
                pd[2] = val2;
                if (val == grayTransparentAlpha) {
                    pd[3] = 0;
                } else {
                    pd[3] = maxOpacity;
                }
                
                dst.setPixel(dstX, y, pd);
                dstX += step;
            }
            break;
        }
    }

    /**
     * Reads in an image of a given size and returns it as a 
     * WritableRaster.
     */
    private void decodePass(WritableRaster imRas,
                            int xOffset, int yOffset,
                            int xStep, int yStep,
                            int passWidth, int passHeight) {
        if ((passWidth == 0) || (passHeight == 0)) {
            return;
        }

        int bytesPerRow = (inputBands*passWidth*bitDepth + 7)/8;
        int eltsPerRow = (bitDepth == 16) ? bytesPerRow/2 : bytesPerRow;
        byte[] curr = new byte[bytesPerRow];
        byte[] prior = new byte[bytesPerRow];

        // Create a 1-row tall Raster to hold the data
        WritableRaster passRow =
            createRaster(passWidth, 1, inputBands,
                         eltsPerRow,
                         bitDepth);
        DataBuffer dataBuffer = passRow.getDataBuffer();
        int type = dataBuffer.getDataType();
        byte[] byteData = null;
        short[] shortData = null;
        if (type == DataBuffer.TYPE_BYTE) {
            byteData = ((DataBufferByte)dataBuffer).getData();
        } else {
            shortData = ((DataBufferUShort)dataBuffer).getData();
        }

        // Decode the (sub)image row-by-row
        int srcY, dstY;
        for (srcY = 0, dstY = yOffset;
             srcY < passHeight;
             srcY++, dstY += yStep) {
            // Read the filter type byte and a row of data
            int filter = 0;
            try {
                filter = dataStream.read();
                dataStream.readFully(curr, 0, bytesPerRow);
            } catch (Exception e) {
                e.printStackTrace();
            }

            switch (filter) {
            case PNG_FILTER_NONE:
                break;
            case PNG_FILTER_SUB:
                decodeSubFilter(curr, bytesPerRow, bytesPerPixel);
                break;
            case PNG_FILTER_UP:
                decodeUpFilter(curr, prior, bytesPerRow);
                break;
            case PNG_FILTER_AVERAGE:
                decodeAverageFilter(curr, prior, bytesPerRow, bytesPerPixel);
                break;
            case PNG_FILTER_PAETH:
                decodePaethFilter(curr, prior, bytesPerRow, bytesPerPixel);
                break;
            default:
                // Error -- uknown filter type
                String msg = PropertyUtil.getString("PNGImageDecoder16");
                throw new RuntimeException(msg);
            }

            // Copy data into passRow byte by byte
            if (bitDepth < 16) {
                System.arraycopy(curr, 0, byteData, 0, bytesPerRow);
            } else {
                int idx = 0;
                for (int j = 0; j < eltsPerRow; j++) {
                    shortData[j] =
                        (short)((curr[idx] << 8) | (curr[idx + 1] & 0xff));
                    idx += 2;
                }
            }

            processPixels(postProcess,
                          passRow, imRas, xOffset, xStep, dstY, passWidth);

            // Swap curr and prior
            byte[] tmp = prior;
            prior = curr;
            curr = tmp;
        }
    }

    private void decodeImage(boolean useInterlacing) {
	int width = bounds.width;
	int height = bounds.height;

        if (!useInterlacing) {
            decodePass(theTile, 0, 0, 1, 1, width, height);
        } else {
            decodePass(theTile, 0, 0, 8, 8, (width + 7)/8, (height + 7)/8);
            decodePass(theTile, 4, 0, 8, 8, (width + 3)/8, (height + 7)/8);
            decodePass(theTile, 0, 4, 4, 8, (width + 3)/4, (height + 3)/8);
            decodePass(theTile, 2, 0, 4, 4, (width + 1)/4, (height + 3)/4);
            decodePass(theTile, 0, 2, 2, 4, (width + 1)/2, (height + 1)/4);
            decodePass(theTile, 1, 0, 2, 2, width/2, (height + 1)/2);
            decodePass(theTile, 0, 1, 1, 2, width, height/2);
        }
    }

    public WritableRaster copyData(WritableRaster wr) {
        GraphicsUtil.copyData(theTile, wr);
        return wr;
    }

    // RenderedImage stuff
    public Raster getTile(int tileX, int tileY) {
        if (tileX != 0 || tileY != 0) {
            // Error -- bad tile requested
            String msg = PropertyUtil.getString("PNGImageDecoder17");
            throw new IllegalArgumentException(msg);
        }
        return theTile;
    }
}
