/*
 * $Id: af5f976075e3d212992b11d62884023a0aec3704 $
 *
 * This file is part of the iText (R) project.
 * Copyright (c) 1998-2015 iText Group NV
 * Authors: Bruno Lowagie, Paulo Soares, et al.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU Affero General Public License version 3
 * as published by the Free Software Foundation with the addition of the
 * following permission added to Section 15 as permitted in Section 7(a):
 * FOR ANY PART OF THE COVERED WORK IN WHICH THE COPYRIGHT IS OWNED BY
 * ITEXT GROUP. ITEXT GROUP DISCLAIMS THE WARRANTY OF NON INFRINGEMENT
 * OF THIRD PARTY RIGHTS
 *
 * This program 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 Affero General Public License for more details.
 * You should have received a copy of the GNU Affero General Public License
 * along with this program; if not, see http://www.gnu.org/licenses or write to
 * the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
 * Boston, MA, 02110-1301 USA, or download the license from the following URL:
 * http://itextpdf.com/terms-of-use/
 *
 * The interactive user interfaces in modified source and object code versions
 * of this program must display Appropriate Legal Notices, as required under
 * Section 5 of the GNU Affero General Public License.
 *
 * In accordance with Section 7(b) of the GNU Affero General Public License,
 * a covered work must retain the producer line in every PDF that is created
 * or manipulated using iText.
 *
 * You can be released from the requirements of the license by purchasing
 * a commercial license. Buying such a license is mandatory as soon as you
 * develop commercial activities involving the iText software without
 * disclosing the source code of your own applications.
 * These activities include: offering paid services to customers as an ASP,
 * serving PDFs on the fly in a web application, shipping iText with a closed
 * source product.
 *
 * For more information, please contact iText Software Corp. at this
 * address: sales@itextpdf.com
 */

/*
 * This code is based on a series of source files originally released
 * by SUN in the context of the JAI project. The original code was released 
 * under the BSD license in a specific wording. In a mail dating from
 * January 23, 2008, Brian Burkhalter (@sun.com) gave us permission
 * to use the code under the following version of the BSD license:
 *
 * Copyright (c) 2005 Sun Microsystems, Inc. All  Rights Reserved.
 * 
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met: 
 * 
 * - Redistribution of source code must retain the above copyright 
 *   notice, this  list of conditions and the following disclaimer.
 * 
 * - Redistribution 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.
 * 
 * Neither the name of Sun Microsystems, Inc. or the names of 
 * contributors may be used to endorse or promote products derived 
 * from this software without specific prior written permission.
 * 
 * This software is provided "AS IS," without a warranty of any 
 * kind. ALL EXPRESS OR IMPLIED CONDITIONS, REPRESENTATIONS AND 
 * WARRANTIES, INCLUDING ANY IMPLIED WARRANTY OF MERCHANTABILITY, 
 * FITNESS FOR A PARTICULAR PURPOSE OR NON-INFRINGEMENT, ARE HEREBY
 * EXCLUDED. SUN MIDROSYSTEMS, INC. ("SUN") AND ITS LICENSORS SHALL 
 * NOT BE LIABLE FOR ANY DAMAGES SUFFERED BY LICENSEE AS A RESULT OF 
 * USING, MODIFYING OR DISTRIBUTING THIS SOFTWARE OR ITS
 * DERIVATIVES. IN NO EVENT WILL SUN OR ITS LICENSORS BE LIABLE FOR 
 * ANY LOST REVENUE, PROFIT OR DATA, OR FOR DIRECT, INDIRECT, SPECIAL,
 * CONSEQUENTIAL, INCIDENTAL OR PUNITIVE DAMAGES, HOWEVER CAUSED AND
 * REGARDLESS OF THE THEORY OF LIABILITY, ARISING OUT OF THE USE OF OR
 * INABILITY TO USE THIS SOFTWARE, EVEN IF SUN HAS BEEN ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGES. 
 * 
 * You acknowledge that this software is not designed or intended for 
 * use in the design, construction, operation or maintenance of any 
 * nuclear facility.
 */

package com.itextpdf.text.pdf.codec;

import com.itextpdf.text.pdf.ICC_Profile;
import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.DataInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.net.URL;
import java.util.zip.Inflater;
import java.util.zip.InflaterInputStream;
import com.itextpdf.text.error_messages.MessageLocalization;

import com.itextpdf.text.ExceptionConverter;
import com.itextpdf.text.Image;
import com.itextpdf.text.ImgRaw;
import com.itextpdf.text.Utilities;
import com.itextpdf.text.pdf.ByteBuffer;
import com.itextpdf.text.pdf.PdfArray;
import com.itextpdf.text.pdf.PdfDictionary;
import com.itextpdf.text.pdf.PdfLiteral;
import com.itextpdf.text.pdf.PdfName;
import com.itextpdf.text.pdf.PdfNumber;
import com.itextpdf.text.pdf.PdfObject;
import com.itextpdf.text.pdf.PdfReader;
import com.itextpdf.text.pdf.PdfString;

/** Reads a PNG image. All types of PNG can be read.
 * <p>
 * It is based in part in the JAI codec.
 *
 * @author  Paulo Soares
 */
public class PngImage {
/** Some PNG specific values. */
    public static final int[] PNGID = {137, 80, 78, 71, 13, 10, 26, 10};
    
/** A PNG marker. */
    public static final String IHDR = "IHDR";
    
/** A PNG marker. */
    public static final String PLTE = "PLTE";
    
/** A PNG marker. */
    public static final String IDAT = "IDAT";
    
/** A PNG marker. */
    public static final String IEND = "IEND";
    
/** A PNG marker. */
    public static final String tRNS = "tRNS";
    
/** A PNG marker. */
    public static final String pHYs = "pHYs";
    
/** A PNG marker. */
    public static final String gAMA = "gAMA";
    
/** A PNG marker. */
    public static final String cHRM = "cHRM";
    
/** A PNG marker. */
    public static final String sRGB = "sRGB";
    
/** A PNG marker. */
    public static final String iCCP = "iCCP";
    
    private static final int TRANSFERSIZE = 4096;
    private static final int PNG_FILTER_NONE = 0;
    private static final int PNG_FILTER_SUB = 1;
    private static final int PNG_FILTER_UP = 2;
    private static final int PNG_FILTER_AVERAGE = 3;
    private static final int PNG_FILTER_PAETH = 4;
    private static final PdfName intents[] = {PdfName.PERCEPTUAL,
        PdfName.RELATIVECOLORIMETRIC,PdfName.SATURATION,PdfName.ABSOLUTECOLORIMETRIC};
    
    InputStream is;
    DataInputStream dataStream;
    int width;
    int height;
    int bitDepth;
    int colorType;
    int compressionMethod;
    int filterMethod;
    int interlaceMethod;
    PdfDictionary additional = new PdfDictionary();
    byte image[];
    byte smask[];
    byte trans[];
    NewByteArrayOutputStream idat = new NewByteArrayOutputStream();
    int dpiX;
    int dpiY;
    float XYRatio;
    boolean genBWMask;
    boolean palShades;
    int transRedGray = -1;
    int transGreen = -1;
    int transBlue = -1;
    int inputBands;
    int bytesPerPixel; // number of bytes per input pixel
    byte colorTable[];
    float gamma = 1f;
    boolean hasCHRM = false;
    float xW, yW, xR, yR, xG, yG, xB, yB;
    PdfName intent;
    ICC_Profile icc_profile;

    
    
    /** Creates a new instance of PngImage */
    PngImage(InputStream is) {
        this.is = is;
    }
    
    /** Reads a PNG from an url.
     * @param url the url
     * @throws IOException on error
     * @return the image
     */    
    public static Image getImage(URL url) throws IOException {
        InputStream is = null;
        try {
            is = url.openStream();
            Image img = getImage(is);
            img.setUrl(url);
            return img;
        }
        finally {
            if (is != null) {
                is.close();
            }
        }
    }
    
    /** Reads a PNG from a stream.
     * @param is the stream
     * @throws IOException on error
     * @return the image
     */    
    public static Image getImage(InputStream is) throws IOException {
        PngImage png = new PngImage(is);
        return png.getImage();
    }
    
    /** Reads a PNG from a file.
     * @param file the file
     * @throws IOException on error
     * @return the image
     */    
    public static Image getImage(String file) throws IOException {
        return getImage(Utilities.toURL(file));
    }
    
    /** Reads a PNG from a byte array.
     * @param data the byte array
     * @throws IOException on error
     * @return the image
     */    
    public static Image getImage(byte data[]) throws IOException {
        ByteArrayInputStream is = new ByteArrayInputStream(data);
        Image img = getImage(is);
        img.setOriginalData(data);
        return img;
    }
    
    boolean checkMarker(String s) {
        if (s.length() != 4)
            return false;
        for (int k = 0; k < 4; ++k) {
            char c = s.charAt(k);
            if ((c < 'a' || c > 'z') && (c < 'A' || c > 'Z'))
                return false;
        }
        return true;
    }
    
    void readPng() throws IOException {
        for (int i = 0; i < PNGID.length; i++) {
            if (PNGID[i] != is.read())	{
                throw new IOException(MessageLocalization.getComposedMessage("file.is.not.a.valid.png"));
            }
        }
        byte buffer[] = new byte[TRANSFERSIZE];
        while (true) {
            int len = getInt(is);
            String marker = getString(is);
            if (len < 0 || !checkMarker(marker))
                throw new IOException(MessageLocalization.getComposedMessage("corrupted.png.file"));
            if (IDAT.equals(marker)) {
                int size;
                while (len != 0) {
                    size = is.read(buffer, 0, Math.min(len, TRANSFERSIZE));
                    if (size < 0)
                        return;
                    idat.write(buffer, 0, size);
                    len -= size;
                }
            }
            else if (tRNS.equals(marker)) {
                switch (colorType) {
                    case 0:
                        if (len >= 2) {
                            len -= 2;
                            int gray = getWord(is);
                            if (bitDepth == 16)
                                transRedGray = gray;
                            else
                                additional.put(PdfName.MASK, new PdfLiteral("["+gray+" "+gray+"]"));
                        }
                        break;
                    case 2:
                        if (len >= 6) {
                            len -= 6;
                            int red = getWord(is);
                            int green = getWord(is);
                            int blue = getWord(is);
                            if (bitDepth == 16) {
                                transRedGray = red;
                                transGreen = green;
                                transBlue = blue;
                            }
                            else
                                additional.put(PdfName.MASK, new PdfLiteral("["+red+" "+red+" "+green+" "+green+" "+blue+" "+blue+"]"));
                        }
                        break;
                    case 3:
                        if (len > 0) {
                            trans = new byte[len];
                            for (int k = 0; k < len; ++k)
                                trans[k] = (byte)is.read();
                            len = 0;
                        }
                        break;
                }
                Utilities.skip(is, len);
            }
            else if (IHDR.equals(marker)) {
                width = getInt(is);
                height = getInt(is);
                
                bitDepth = is.read();
                colorType = is.read();
                compressionMethod = is.read();
                filterMethod = is.read();
                interlaceMethod = is.read();
            }
            else if (PLTE.equals(marker)) {
                if (colorType == 3) {
                    PdfArray colorspace = new PdfArray();
                    colorspace.add(PdfName.INDEXED);
                    colorspace.add(getColorspace());
                    colorspace.add(new PdfNumber(len / 3 - 1));
                    ByteBuffer colortable = new ByteBuffer();
                    while ((len--) > 0) {
                        colortable.append_i(is.read());
                    }
                    colorspace.add(new PdfString(colorTable = colortable.toByteArray()));
                    additional.put(PdfName.COLORSPACE, colorspace);
                }
                else {
                    Utilities.skip(is, len);
                }
            }
            else if (pHYs.equals(marker)) {
                int dx = getInt(is);
                int dy = getInt(is);
                int unit = is.read();
                if (unit == 1) {
                    dpiX = (int)(dx * 0.0254f + 0.5f);
                    dpiY = (int)(dy * 0.0254f + 0.5f);
                }
                else {
                    if (dy != 0)
                        XYRatio = (float)dx / (float)dy;
                }
            }
            else if (cHRM.equals(marker)) {
                xW = getInt(is) / 100000f;
                yW = getInt(is) / 100000f;
                xR = getInt(is) / 100000f;
                yR = getInt(is) / 100000f;
                xG = getInt(is) / 100000f;
                yG = getInt(is) / 100000f;
                xB = getInt(is) / 100000f;
                yB = getInt(is) / 100000f;
                hasCHRM = !(Math.abs(xW)<0.0001f||Math.abs(yW)<0.0001f||Math.abs(xR)<0.0001f||Math.abs(yR)<0.0001f||Math.abs(xG)<0.0001f||Math.abs(yG)<0.0001f||Math.abs(xB)<0.0001f||Math.abs(yB)<0.0001f);
            }
            else if (sRGB.equals(marker)) {
                int ri = is.read();
                intent = intents[ri];
                gamma = 2.2f;
                xW = 0.3127f;
                yW = 0.329f;
                xR = 0.64f;
                yR = 0.33f;
                xG = 0.3f;
                yG = 0.6f;
                xB = 0.15f;
                yB = 0.06f;
                hasCHRM = true;
            }
            else if (gAMA.equals(marker)) {
                int gm = getInt(is);
                if (gm != 0) {
                    gamma = 100000f / gm;
                    if (!hasCHRM) {
                        xW = 0.3127f;
                        yW = 0.329f;
                        xR = 0.64f;
                        yR = 0.33f;
                        xG = 0.3f;
                        yG = 0.6f;
                        xB = 0.15f;
                        yB = 0.06f;
                        hasCHRM = true;
                    }
                }
            }
            else if (iCCP.equals(marker)) {
                do {
                    --len;
                } while (is.read() != 0);
                is.read();
                --len;
                byte icccom[] = new byte[len];
                int p = 0;
                while (len > 0) {
                    int r = is.read(icccom, p, len);
                    if (r < 0)
                        throw new IOException(MessageLocalization.getComposedMessage("premature.end.of.file"));
                    p += r;
                    len -= r;
                }
                byte iccp[] = PdfReader.FlateDecode(icccom, true);
                icccom = null;
                try {
                    icc_profile = ICC_Profile.getInstance(iccp);
                }
                catch (RuntimeException e) {
                    icc_profile = null;
                }
            }
            else if (IEND.equals(marker)) {
                break;
            }
            else {
                Utilities.skip(is, len);
            }
            Utilities.skip(is, 4);
        }
    }
    
    PdfObject getColorspace() {
        if (icc_profile != null) {
            if ((colorType & 2) == 0)
                return PdfName.DEVICEGRAY;
            else
                return PdfName.DEVICERGB;
        }
        if (gamma == 1f && !hasCHRM) {
            if ((colorType & 2) == 0)
                return PdfName.DEVICEGRAY;
            else
                return PdfName.DEVICERGB;
        }
        else {
            PdfArray array = new PdfArray();
            PdfDictionary dic = new PdfDictionary();
            if ((colorType & 2) == 0) {
                if (gamma == 1f)
                    return PdfName.DEVICEGRAY;
                array.add(PdfName.CALGRAY);
                dic.put(PdfName.GAMMA, new PdfNumber(gamma));
                dic.put(PdfName.WHITEPOINT, new PdfLiteral("[1 1 1]"));
                array.add(dic);
            }
            else {
                PdfObject wp = new PdfLiteral("[1 1 1]");
                array.add(PdfName.CALRGB);
                if (gamma != 1f) {
                    PdfArray gm = new PdfArray();
                    PdfNumber n = new PdfNumber(gamma);
                    gm.add(n);
                    gm.add(n);
                    gm.add(n);
                    dic.put(PdfName.GAMMA, gm);
                }
                if (hasCHRM) {
                    float z = yW*((xG-xB)*yR-(xR-xB)*yG+(xR-xG)*yB);
                    float YA = yR*((xG-xB)*yW-(xW-xB)*yG+(xW-xG)*yB)/z;
                    float XA = YA*xR/yR;
                    float ZA = YA*((1-xR)/yR-1);
                    float YB = -yG*((xR-xB)*yW-(xW-xB)*yR+(xW-xR)*yB)/z;
                    float XB = YB*xG/yG;
                    float ZB = YB*((1-xG)/yG-1);
                    float YC = yB*((xR-xG)*yW-(xW-xG)*yW+(xW-xR)*yG)/z;
                    float XC = YC*xB/yB;
                    float ZC = YC*((1-xB)/yB-1);
                    float XW = XA+XB+XC;
                    float YW = 1;//YA+YB+YC;
                    float ZW = ZA+ZB+ZC;
                    PdfArray wpa = new PdfArray();
                    wpa.add(new PdfNumber(XW));
                    wpa.add(new PdfNumber(YW));
                    wpa.add(new PdfNumber(ZW));
                    wp = wpa;
                    PdfArray matrix = new PdfArray();
                    matrix.add(new PdfNumber(XA));
                    matrix.add(new PdfNumber(YA));
                    matrix.add(new PdfNumber(ZA));
                    matrix.add(new PdfNumber(XB));
                    matrix.add(new PdfNumber(YB));
                    matrix.add(new PdfNumber(ZB));
                    matrix.add(new PdfNumber(XC));
                    matrix.add(new PdfNumber(YC));
                    matrix.add(new PdfNumber(ZC));
                    dic.put(PdfName.MATRIX, matrix);
                }
                dic.put(PdfName.WHITEPOINT, wp);
                array.add(dic);
            }
            return array;
        }
    }
    
    Image getImage() throws IOException {
        readPng();
        try {
            int pal0 = 0;
            int palIdx = 0;
            palShades = false;
            if (trans != null) {
                for (int k = 0; k < trans.length; ++k) {
                    int n = trans[k] & 0xff;
                    if (n == 0) {
                        ++pal0;
                        palIdx = k;
                    }
                    if (n != 0 && n != 255) {
                        palShades = true;
                        break;
                    }
                }
            }
            if ((colorType & 4) != 0)
                palShades = true;
            genBWMask = (!palShades && (pal0 > 1 || transRedGray >= 0));
            if (!palShades && !genBWMask && pal0 == 1) {
                additional.put(PdfName.MASK, new PdfLiteral("["+palIdx+" "+palIdx+"]"));
            }
            boolean needDecode = (interlaceMethod == 1) || (bitDepth == 16) || ((colorType & 4) != 0) || palShades || genBWMask;
            switch (colorType) {
                case 0:
                    inputBands = 1;
                    break;
                case 2:
                    inputBands = 3;
                    break;
                case 3:
                    inputBands = 1;
                    break;
                case 4:
                    inputBands = 2;
                    break;
                case 6:
                    inputBands = 4;
                    break;
            }
            if (needDecode)
                decodeIdat();
            int components = inputBands;
            if ((colorType & 4) != 0)
                --components;
            int bpc = bitDepth;
            if (bpc == 16)
                bpc = 8;
            Image img;
            if (image != null) {
                if (colorType == 3)
                    img = new ImgRaw(width, height, components, bpc, image);
                else
                    img = Image.getInstance(width, height, components, bpc, image);
            }
            else {
                img = new ImgRaw(width, height, components, bpc, idat.toByteArray());
                img.setDeflated(true);
                PdfDictionary decodeparms = new PdfDictionary();
                decodeparms.put(PdfName.BITSPERCOMPONENT, new PdfNumber(bitDepth));
                decodeparms.put(PdfName.PREDICTOR, new PdfNumber(15));
                decodeparms.put(PdfName.COLUMNS, new PdfNumber(width));
                decodeparms.put(PdfName.COLORS, new PdfNumber((colorType == 3 || (colorType & 2) == 0) ? 1 : 3));
                additional.put(PdfName.DECODEPARMS, decodeparms);
            }
            if (additional.get(PdfName.COLORSPACE) == null)
                additional.put(PdfName.COLORSPACE, getColorspace());
            if (intent != null)
                additional.put(PdfName.INTENT, intent);
            if (additional.size() > 0)
                img.setAdditional(additional);
            if (icc_profile != null)
                img.tagICC(icc_profile);
            if (palShades) {
                Image im2 = Image.getInstance(width, height, 1, 8, smask);
                im2.makeMask();
                img.setImageMask(im2);
            }
            if (genBWMask) {
                Image im2 = Image.getInstance(width, height, 1, 1, smask);
                im2.makeMask();
                img.setImageMask(im2);
            }
            img.setDpi(dpiX, dpiY);
            img.setXYRatio(XYRatio);
            img.setOriginalType(Image.ORIGINAL_PNG);
            return img;
        }
        catch (Exception e) {
            throw new ExceptionConverter(e);
        }
    }
    
    void decodeIdat() {
        int nbitDepth = bitDepth;
        if (nbitDepth == 16)
            nbitDepth = 8;
        int size = -1;
        bytesPerPixel = (bitDepth == 16) ? 2 : 1;
        switch (colorType) {
            case 0:
                size = (nbitDepth * width + 7) / 8 * height;
                break;
            case 2:
                size = width * 3 * height;
                bytesPerPixel *= 3;
                break;
            case 3:
                if (interlaceMethod == 1)
                    size = (nbitDepth * width + 7) / 8 * height;
                bytesPerPixel = 1;
                break;
            case 4:
                size = width * height;
                bytesPerPixel *= 2;
                break;
            case 6:
                size = width * 3 * height;
                bytesPerPixel *= 4;
                break;
        }
        if (size >= 0)
            image = new byte[size];
        if (palShades)
            smask = new byte[width * height];
        else if (genBWMask)
            smask = new byte[(width + 7) / 8 * height];
        ByteArrayInputStream bai = new ByteArrayInputStream(idat.getBuf(), 0, idat.size());
        InputStream infStream = new InflaterInputStream(bai, new Inflater());
        dataStream = new DataInputStream(infStream);
        
        if (interlaceMethod != 1) {
            decodePass(0, 0, 1, 1, width, height);
        }
        else {
            decodePass(0, 0, 8, 8, (width + 7)/8, (height + 7)/8);
            decodePass(4, 0, 8, 8, (width + 3)/8, (height + 7)/8);
            decodePass(0, 4, 4, 8, (width + 3)/4, (height + 3)/8);
            decodePass(2, 0, 4, 4, (width + 1)/4, (height + 3)/4);
            decodePass(0, 2, 2, 4, (width + 1)/2, (height + 1)/4);
            decodePass(1, 0, 2, 2, width/2, (height + 1)/2);
            decodePass(0, 1, 1, 2, width, height/2);
        }
        
    }
    
    void decodePass( 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;
        byte[] curr = new byte[bytesPerRow];
        byte[] prior = new byte[bytesPerRow];
        
        // 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) {
                // empty on purpose
            }
            
            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
                    throw new RuntimeException(MessageLocalization.getComposedMessage("png.filter.unknown"));
            }
            
            processPixels(curr, xOffset, xStep, dstY, passWidth);
            
            // Swap curr and prior
            byte[] tmp = prior;
            prior = curr;
            curr = tmp;
        }
    }
    
    void processPixels(byte curr[], int xOffset, int step, int y, int width) {
        int srcX, dstX;

        int out[] = getPixel(curr);
        int sizes = 0;
        switch (colorType) {
            case 0:
            case 3:
            case 4:
                sizes = 1;
                break;
            case 2:
            case 6:
                sizes = 3;
                break;
        }
        if (image != null) {
            dstX = xOffset;
            int yStride = (sizes*this.width*(bitDepth == 16 ? 8 : bitDepth)+ 7)/8;
            for (srcX = 0; srcX < width; srcX++) {
                setPixel(image, out, inputBands * srcX, sizes, dstX, y, bitDepth, yStride);
                dstX += step;
            }
        }
        if (palShades) {
            if ((colorType & 4) != 0) {
                if (bitDepth == 16) {
                    for (int k = 0; k < width; ++k)
                        out[k * inputBands + sizes] >>>= 8;
                }
                int yStride = this.width;
                dstX = xOffset;
                for (srcX = 0; srcX < width; srcX++) {
                    setPixel(smask, out, inputBands * srcX + sizes, 1, dstX, y, 8, yStride);
                    dstX += step;
                }
            }
            else { //colorType 3
                int yStride = this.width;
                int v[] = new int[1];
                dstX = xOffset;
                for (srcX = 0; srcX < width; srcX++) {
                    int idx = out[srcX];
                    if (idx < trans.length)
                        v[0] = trans[idx];
                    else
                    	v[0] = 255; // Patrick Valsecchi
                    setPixel(smask, v, 0, 1, dstX, y, 8, yStride);
                    dstX += step;
                }
            }
        }
        else if (genBWMask) {
            switch (colorType) {
                case 3: {
                    int yStride = (this.width + 7) / 8;
                    int v[] = new int[1];
                    dstX = xOffset;
                    for (srcX = 0; srcX < width; srcX++) {
                        int idx = out[srcX];
                        v[0] = ((idx < trans.length && trans[idx] == 0) ? 1 : 0);
                        setPixel(smask, v, 0, 1, dstX, y, 1, yStride);
                        dstX += step;
                    }
                    break;
                }
                case 0: {
                    int yStride = (this.width + 7) / 8;
                    int v[] = new int[1];
                    dstX = xOffset;
                    for (srcX = 0; srcX < width; srcX++) {
                        int g = out[srcX];
                        v[0] = (g == transRedGray ? 1 : 0);
                        setPixel(smask, v, 0, 1, dstX, y, 1, yStride);
                        dstX += step;
                    }
                    break;
                }
                case 2: {
                    int yStride = (this.width + 7) / 8;
                    int v[] = new int[1];
                    dstX = xOffset;
                    for (srcX = 0; srcX < width; srcX++) {
                        int markRed = inputBands * srcX;
                        v[0] = (out[markRed] == transRedGray && out[markRed + 1] == transGreen 
                            && out[markRed + 2] == transBlue ? 1 : 0);
                        setPixel(smask, v, 0, 1, dstX, y, 1, yStride);
                        dstX += step;
                    }
                    break;
                }
            }
        }
    }
    
    static int getPixel(byte image[], int x, int y, int bitDepth, int bytesPerRow) {
        if (bitDepth == 8) {
            int pos = bytesPerRow * y + x;
            return image[pos] & 0xff;
        }
        else {
            int pos = bytesPerRow * y + x / (8 / bitDepth);
            int v = image[pos] >> (8 - bitDepth * (x % (8 / bitDepth))- bitDepth);
            return v & ((1 << bitDepth) - 1);
        }
    }
    
    static void setPixel(byte image[], int data[], int offset, int size, int x, int y, int bitDepth, int bytesPerRow) {
        if (bitDepth == 8) {
            int pos = bytesPerRow * y + size * x;
            for (int k = 0; k < size; ++k)
                image[pos + k] = (byte)data[k + offset];
        }
        else if (bitDepth == 16) {
            int pos = bytesPerRow * y + size * x;
            for (int k = 0; k < size; ++k)
                image[pos + k] = (byte)(data[k + offset] >>> 8);
        }
        else {
            int pos = bytesPerRow * y + x / (8 / bitDepth);
            int v = data[offset] << (8 - bitDepth * (x % (8 / bitDepth))- bitDepth);
            image[pos] |= v;
        }
    }
    
    int[] getPixel(byte curr[]) {
        switch (bitDepth) {
            case 8: {
                int out[] = new int[curr.length];
                for (int k = 0; k < out.length; ++k)
                    out[k] = curr[k] & 0xff;
                return out;
            }
            case 16: {
                int out[] = new int[curr.length / 2];
                for (int k = 0; k < out.length; ++k)
                    out[k] = ((curr[k * 2] & 0xff) << 8) + (curr[k * 2 + 1] & 0xff);
                return out;
            }
            default: {
                int out[] = new int[curr.length * 8 / bitDepth];
                int idx = 0;
                int passes = 8 / bitDepth;
                int mask = (1 << bitDepth) - 1;
                for (int k = 0; k < curr.length; ++k) {
                    for (int j = passes - 1; j >= 0; --j) {
                        out[idx++] = (curr[k] >>> (bitDepth * j)) & mask; 
                    }
                }
                return out;
            }
        }
    }
    
    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));
        }
    }
    
    static class NewByteArrayOutputStream extends ByteArrayOutputStream {
        public byte[] getBuf() {
            return buf;
        }
    }

/**
 * Gets an <CODE>int</CODE> from an <CODE>InputStream</CODE>.
 *
 * @param		is      an <CODE>InputStream</CODE>
 * @return		the value of an <CODE>int</CODE>
 */
    
    public static final int getInt(InputStream is) throws IOException {
        return (is.read() << 24) + (is.read() << 16) + (is.read() << 8) + is.read();
    }
    
/**
 * Gets a <CODE>word</CODE> from an <CODE>InputStream</CODE>.
 *
 * @param		is      an <CODE>InputStream</CODE>
 * @return		the value of an <CODE>int</CODE>
 */
    
    public static final int getWord(InputStream is) throws IOException {
        return (is.read() << 8) + is.read();
    }
    
/**
 * Gets a <CODE>String</CODE> from an <CODE>InputStream</CODE>.
 *
 * @param		is      an <CODE>InputStream</CODE>
 * @return		the value of an <CODE>int</CODE>
 */
    
    public static final String getString(InputStream is) throws IOException {
        StringBuffer buf = new StringBuffer();
        for (int i = 0; i < 4; i++) {
            buf.append((char)is.read());
        }
        return buf.toString();
    }

}
