/*****************************************************************************
 * Copyright (C) The Apache Software Foundation. All rights reserved.        *
 * ------------------------------------------------------------------------- *
 * This software is published under the terms of the Apache Software License *
 * version 1.1, a copy of which has been included with this distribution in  *
 * the LICENSE file.                                                         *
 *****************************************************************************/

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

import java.awt.image.ColorModel;
import java.awt.image.IndexColorModel;
import java.awt.image.RenderedImage;
import java.awt.image.SampleModel;
import java.util.Date;
import java.util.Vector;

/**
 * An instance of <code>ImageEncodeParam</code> for encoding images in
 * the PNG format.
 *
 * <p><b> This class is not a committed part of the JAI API.  It may
 * be removed or changed in future releases of JAI.</b>
 */
public abstract class PNGEncodeParam implements ImageEncodeParam {

    /** Constant for use with the sRGB chunk. */
    public static final int INTENT_PERCEPTUAL = 0;

    /** Constant for use with the sRGB chunk. */
    public static final int INTENT_RELATIVE = 1;

    /** Constant for use with the sRGB chunk. */
    public static final int INTENT_SATURATION = 2;

    /** Constant for use with the sRGB chunk. */
    public static final int INTENT_ABSOLUTE = 3;

    /** Constant for use in filtering. */
    public static final int PNG_FILTER_NONE = 0;

    /** Constant for use in filtering. */
    public static final int PNG_FILTER_SUB = 1;

    /** Constant for use in filtering. */
    public static final int PNG_FILTER_UP = 2;

    /** Constant for use in filtering. */
    public static final int PNG_FILTER_AVERAGE = 3;

    /** Constant for use in filtering. */
    public static final int PNG_FILTER_PAETH = 4;


    /**
     * Returns an instance of <code>PNGEncodeParam.Palette</code>,
     * <code>PNGEncodeParam.Gray</code>, or
     * <code>PNGEncodeParam.RGB</code> appropriate for encoding
     * the given image.
     *
     * <p> If the image has an <code>IndexColorModel</code>, an
     * instance of <code>PNGEncodeParam.Palette</code> is returned.
     * Otherwise, if the image has 1 or 2 bands an instance of
     * <code>PNGEncodeParam.Gray</code> is returned.  In all other
     * cases an instance of <code>PNGEncodeParam.RGB</code> is
     * returned.
     *
     * <p> Note that this method does not provide any guarantee that
     * the given image will be successfully encoded by the PNG
     * encoder, as it only performs a very superficial analysis of
     * the image structure. 
     */
    public static PNGEncodeParam getDefaultEncodeParam(RenderedImage im) {
        ColorModel colorModel = im.getColorModel();
        if (colorModel instanceof IndexColorModel) {
            return new PNGEncodeParam.Palette();
        }

        SampleModel sampleModel = im.getSampleModel();
        int numBands = sampleModel.getNumBands();

        if (numBands == 1 || numBands == 2) {
            return new PNGEncodeParam.Gray();
        } else {
            return new PNGEncodeParam.RGB();
        }
    }

    public static class Palette extends PNGEncodeParam {

        /** Constructs an instance of <code>PNGEncodeParam.Palette</code>. */
        public Palette() {}

        // bKGD chunk
        
        private boolean backgroundSet = false;
        
        /**
         * Suppresses the 'bKGD' chunk from being output.
         */
        public void unsetBackground() {
            backgroundSet = false;
        }
        
        /**
         * Returns true if a 'bKGD' chunk will be output.
         */
        public boolean isBackgroundSet() {
            return backgroundSet;
        }

        /**
         * Sets the desired bit depth for a palette image.  The bit
         * depth must be one of 1, 2, 4, or 8, or else an
         * <code>IllegalArgumentException</code> will be thrown.
         */
        public void setBitDepth(int bitDepth) {
            if (bitDepth != 1 && bitDepth != 2 && bitDepth != 4 &&
                bitDepth != 8) {
                throw new IllegalArgumentException(PropertyUtil.getString("PNGEncodeParam2"));
            }
            this.bitDepth = bitDepth;
            bitDepthSet = true;
        }
    
        // PLTE chunk

        private int[] palette = null;
        private boolean paletteSet = false;

        /**
         * Sets the RGB palette of the image to be encoded.
         * The <code>rgb</code> parameter contains alternating
         * R, G, B values for each color index used in the image.
         * The number of elements must be a multiple of 3 between
         * 3 and 3*256.
         *
         * <p> The 'PLTE' chunk will encode this information.
         *
         * @param rgb An array of <code>int</code>s.
         */
        public void setPalette(int[] rgb) {
            if (rgb.length < 1*3 || rgb.length > 256*3) {
		throw new 
		  IllegalArgumentException(PropertyUtil.getString("PNGEncodeParam0"));
            }
            if ((rgb.length % 3) != 0) {
                throw new 
         	  IllegalArgumentException(PropertyUtil.getString("PNGEncodeParam1"));
            }
            
            palette = (int[])(rgb.clone());
            paletteSet = true;
        }
        
        /**
         * Returns the current RGB palette.
         *
         * <p> If the palette has not previously been set, or has been
         * unset, an <code>IllegalStateException</code> will be thrown.
         *
         * @throws IllegalStateException if the palette is not set.
         *
         * @return An array of <code>int</code>s.
         */
        public int[] getPalette() {
            if (!paletteSet) {
                throw new IllegalStateException(PropertyUtil.getString("PNGEncodeParam3"));
            }
            return (int[])(palette.clone());
        }

        /**
         * Suppresses the 'PLTE' chunk from being output.
         */
        public void unsetPalette() {
            palette = null;
            paletteSet = false;
        }
        
        /**
         * Returns true if a 'PLTE' chunk will be output.
         */
        public boolean isPaletteSet() {
            return paletteSet;
        }

        // bKGD chunk
        
        private int backgroundPaletteIndex;
        
        /**
         * Sets the palette index of the suggested background color.
         *
         * <p> The 'bKGD' chunk will encode this information.
         */
        public void setBackgroundPaletteIndex(int index) {
            backgroundPaletteIndex = index;
            backgroundSet = true;
        }
        
        /**
         * Returns the palette index of the suggested background color.
         *
         * <p> If the background palette index has not previously been
         * set, or has been unset, an
         * <code>IllegalStateException</code> will be thrown.
         *
         * @throws IllegalStateException if the palette index is not set.
         */
        public int getBackgroundPaletteIndex() {
            if (!backgroundSet) {
                throw new IllegalStateException(PropertyUtil.getString("PNGEncodeParam4"));
            }
            return backgroundPaletteIndex;
        }

        // tRNS chunk

        private int[] transparency;

        /**
         * Sets the alpha values associated with each palette entry.
         * The <code>alpha</code> parameter should have as many entries
         * as there are RGB triples in the palette.
         *
         * <p> The 'tRNS' chunk will encode this information.
         */
        public void setPaletteTransparency(byte[] alpha) {
            transparency = new int[alpha.length];
            for (int i = 0; i < alpha.length; i++) {
                transparency[i] = alpha[i] & 0xff;
            }
            transparencySet = true;
        }
        
        /**
         * Returns the alpha values associated with each palette entry.
         *
         * <p> If the palette transparency has not previously been
         * set, or has been unset, an
         * <code>IllegalStateException</code> will be thrown.
         *
         * @throws IllegalStateException if the palette transparency is
         *        not set.
         */
        public byte[] getPaletteTransparency() {
            if (!transparencySet) {
                throw new IllegalStateException(PropertyUtil.getString("PNGEncodeParam5"));
            }
            byte[] alpha = new byte[transparency.length];
            for (int i = 0; i < alpha.length; i++) {
                alpha[i] = (byte)transparency[i];
            }
            return alpha;
        }
    }

    public static class Gray extends PNGEncodeParam {

        /** Constructs an instance of <code>PNGEncodeParam.Gray</code>. */
        public Gray() {}

        // bKGD chunk
        
        private boolean backgroundSet = false;
        
        /**
         * Suppresses the 'bKGD' chunk from being output.
         */
        public void unsetBackground() {
            backgroundSet = false;
        }
        
        /**
         * Returns true if a 'bKGD' chunk will be output.
         */
        public boolean isBackgroundSet() {
            return backgroundSet;
        }

        /**
         * Sets the desired bit depth for a grayscale image.  The bit
         * depth must be one of 1, 2, 4, 8, or 16.
         *
         * <p> When encoding a source image of a greater bit depth,
         * pixel values will be clamped to the smaller range after
         * shifting by the value given by <code>getBitShift()</code>.
         * When encoding a source image of a smaller bit depth, pixel
         * values will be shifted and left-filled with zeroes.
         */
        public void setBitDepth(int bitDepth) {
            if (bitDepth != 1 && bitDepth != 2 && bitDepth != 4 &&
                bitDepth != 8 && bitDepth != 16) {
                throw new IllegalArgumentException();
            }
            this.bitDepth = bitDepth;
            bitDepthSet = true;
        }
    
        // bKGD chunk
        
        private int backgroundPaletteGray;

        /**
         * Sets the suggested gray level of the background.
         *
         * <p> The 'bKGD' chunk will encode this information.
         */
        public void setBackgroundGray(int gray) {
            backgroundPaletteGray = gray;
            backgroundSet = true;
        }
        
        /**
         * Returns the suggested gray level of the background.
         *
         * <p> If the background gray level has not previously been
         * set, or has been unset, an
         * <code>IllegalStateException</code> will be thrown.
         *
         * @throws IllegalStateException if the background gray level
         *        is not set.
         */
        public int getBackgroundGray() {
            if (!backgroundSet) {
                throw new IllegalStateException(PropertyUtil.getString("PNGEncodeParam6"));
            }
            return backgroundPaletteGray;
        }

        // tRNS chunk

        private int[] transparency;

        /**
         * Sets the gray value to be used to denote transparency.
         *
         * <p> Setting this attribute will cause the alpha channel
         * of the input image to be ignored.
         *
         * <p> The 'tRNS' chunk will encode this information.
         */
        public void setTransparentGray(int transparentGray) {
            transparency = new int[1];
            transparency[0] = transparentGray;
            transparencySet = true;
        }
        
        /**
         * Returns the gray value to be used to denote transparency.
         *
         * <p> If the transparent gray value has not previously been
         * set, or has been unset, an
         * <code>IllegalStateException</code> will be thrown.
         *
         * @throws IllegalStateException if the transparent gray value
         *        is not set.
         */
        public int getTransparentGray() {
            if (!transparencySet) {
                throw new IllegalStateException(PropertyUtil.getString("PNGEncodeParam7"));
            }
            int gray = transparency[0];
            return gray;
        }

        private int bitShift;
        private boolean bitShiftSet = false;

        /**
         * Sets the desired bit shift for a grayscale image.
         * Pixels in the source image will be shifted right by
         * the given amount prior to being clamped to the maximum
         * value given by the encoded image's bit depth.
         */
        public void setBitShift(int bitShift) {
            if (bitShift < 0) {
                throw new RuntimeException();
            }
            this.bitShift = bitShift;
            bitShiftSet = true;
        }

        /** 
         * Returns the desired bit shift for a grayscale image.
         *
         * <p> If the bit shift has not previously been set, or has been
         * unset, an <code>IllegalStateException</code> will be thrown.
         *
         * @throws IllegalStateException if the bit shift is not set.
         */
        public int getBitShift() {
            if (!bitShiftSet) {
                throw new IllegalStateException(PropertyUtil.getString("PNGEncodeParam8"));
            }
            return bitShift;
        }

        /**
         * Suppresses the setting of the bit shift of a grayscale image.
         * Pixels in the source image will not be shifted prior to encoding.
         */
        public void unsetBitShift() {
            bitShiftSet = false;
        }

        /**
         * Returns true if the bit shift has been set.
         */
        public boolean isBitShiftSet() {
            return bitShiftSet;
        }

        /**
         * Returns true if the bit depth has been set.
         */
        public boolean isBitDepthSet() {
            return bitDepthSet;
        }
    }

    public static class RGB extends PNGEncodeParam {

        /** Constructs an instance of <code>PNGEncodeParam.RGB</code>. */
        public RGB() {}

        // bKGD chunk
        
        private boolean backgroundSet = false;
        
        /**
         * Suppresses the 'bKGD' chunk from being output.
         */
        public void unsetBackground() {
            backgroundSet = false;
        }
        
        /**
         * Returns true if a 'bKGD' chunk will be output.
         */
        public boolean isBackgroundSet() {
            return backgroundSet;
        }

        /**
         * Sets the desired bit depth for an RGB image.  The bit
         * depth must be 8 or 16.
         */
        public void setBitDepth(int bitDepth) {
            if (bitDepth != 8 && bitDepth != 16) {
                throw new RuntimeException();
            }
            this.bitDepth = bitDepth;
            bitDepthSet = true;
        }
    
        // bKGD chunk

        private int[] backgroundRGB;

        /**
         * Sets the RGB value of the suggested background color.
         * The <code>rgb</code> parameter should have 3 entries. 
         *
         * <p> The 'bKGD' chunk will encode this information.
         */
        public void setBackgroundRGB(int[] rgb) {
            if (rgb.length != 3) {
                throw new RuntimeException();
            }
            backgroundRGB = rgb;
            backgroundSet = true;
        }
        
        /**
         * Returns the RGB value of the suggested background color.
         *
         * <p> If the background color has not previously been set, or has been
         * unset, an <code>IllegalStateException</code> will be thrown.
         *
         * @throws IllegalStateException if the background color is not set.
         */
        public int[] getBackgroundRGB() {
            if (!backgroundSet) {
                throw new IllegalStateException(PropertyUtil.getString("PNGEncodeParam9"));
            }
            return backgroundRGB;
        }

        // tRNS chunk

        private int[] transparency;
        
        /**
         * Sets the RGB value to be used to denote transparency.
         *
         * <p> Setting this attribute will cause the alpha channel
         * of the input image to be ignored.
         *
         * <p> The 'tRNS' chunk will encode this information.
         */
        public void setTransparentRGB(int[] transparentRGB) {
            transparency = (int[])(transparentRGB.clone());
            transparencySet = true;
        }
        
        /**
         * Returns the RGB value to be used to denote transparency.
         *
         * <p> If the transparent color has not previously been set,
         * or has been unset, an <code>IllegalStateException</code>
         * will be thrown.
         *
         * @throws IllegalStateException if the transparent color is not set.
         */
        public int[] getTransparentRGB() {
            if (!transparencySet) {
                throw new IllegalStateException(PropertyUtil.getString("PNGEncodeParam10"));
            }
            return (int[])(transparency.clone());
        }
    }

    protected int bitDepth;
    protected boolean bitDepthSet = false;

    /**
     * Sets the desired bit depth of an image.
     */
    public abstract void setBitDepth(int bitDepth);
    
    /** 
     * Returns the desired bit depth for a grayscale image.
     *
     * <p> If the bit depth has not previously been set, or has been
     * unset, an <code>IllegalStateException</code> will be thrown.
     *
     * @throws IllegalStateException if the bit depth is not set.
     */
    public int getBitDepth() {
        if (!bitDepthSet) {
            throw new IllegalStateException(PropertyUtil.getString("PNGEncodeParam11"));
        }
        return bitDepth;
    }

    /**
     * Suppresses the setting of the bit depth of a grayscale image.
     * The depth of the encoded image will be inferred from the source
     * image bit depth, rounded up to the next power of 2 between 1 
     * and 16.
     */
    public void unsetBitDepth() {
        bitDepthSet = false;
    }

    private boolean useInterlacing = false;

    /**
     * Turns Adam7 interlacing on or off.
     */
    public void setInterlacing(boolean useInterlacing) {
        this.useInterlacing = useInterlacing;
    }

    /**
     * Returns <code>true</code> if Adam7 interlacing will be used.
     */
    public boolean getInterlacing() {
        return useInterlacing;
    }
    
    // bKGD chunk - delegate to subclasses

    // In JAI 1.0, 'backgroundSet' was private.  The JDK 1.2 compiler
    // was lenient and incorrectly allowed this variable to be
    // accessed from the subclasses.  The JDK 1.3 compiler correctly
    // flags this as a use of a non-static variable in a static
    // context.  Changing 'backgroundSet' to protected would have
    // solved the problem, but would have introduced a visible API
    // change.  Thus we are forced to adopt the solution of placing a
    // separate private variable in each subclass and providing
    // separate implementations of 'unsetBackground' and
    // 'isBackgroundSet' in each concrete subclass.

    /**
     * Suppresses the 'bKGD' chunk from being output.
     * For API compatibility with JAI 1.0, the superclass
     * defines this method to throw a <code>RuntimeException</code>;
     * accordingly, subclasses must provide their own implementations.
     */
    public void unsetBackground() {
        throw new RuntimeException(PropertyUtil.getString("PNGEncodeParam23"));
    }

    /**
     * Returns true if a 'bKGD' chunk will be output.
     * For API compatibility with JAI 1.0, the superclass
     * defines this method to throw a <code>RuntimeException</code>;
     * accordingly, subclasses must provide their own implementations.
     */
    public boolean isBackgroundSet() {
        throw new RuntimeException(PropertyUtil.getString("PNGEncodeParam24"));
    }

    // cHRM chunk

    private float[] chromaticity = null;
    private boolean chromaticitySet = false;

    /**
     * Sets the white point and primary chromaticities in CIE (x, y)
     * space.
     *
     * <p> The <code>chromaticity</code> parameter should be a
     * <code>float</code> array of length 8 containing the white point
     * X and Y, red X and Y, green X and Y, and blue X and Y values in
     * order.
     *
     * <p> The 'cHRM' chunk will encode this information.
     */
    public void setChromaticity(float[] chromaticity) {
        if (chromaticity.length != 8) {
            throw new IllegalArgumentException();
        }
        this.chromaticity = (float[])(chromaticity.clone());
        chromaticitySet = true;
    }

    /**
     * A convenience method that calls the array version.
     */
    public void setChromaticity(float whitePointX, float whitePointY,
                                float redX, float redY,
                                float greenX, float greenY,
                                float blueX, float blueY) {
        float[] chroma = new float[8];
        chroma[0] = whitePointX;
        chroma[1] = whitePointY;
        chroma[2] = redX;
        chroma[3] = redY;
        chroma[4] = greenX;
        chroma[5] = greenY;
        chroma[6] = blueX;
        chroma[7] = blueY;
        setChromaticity(chroma);
    }

    /**
     * Returns the white point and primary chromaticities in
     * CIE (x, y) space.
     *
     * <p> See the documentation for the <code>setChromaticity</code>
     * method for the format of the returned data.
     *
     * <p> If the chromaticity has not previously been set, or has been
     * unset, an <code>IllegalStateException</code> will be thrown.
     *
     * @throws IllegalStateException if the chromaticity is not set.
     */
    public float[] getChromaticity() {
        if (!chromaticitySet) {
            throw new IllegalStateException(PropertyUtil.getString("PNGEncodeParam12"));
        }
        return (float[])(chromaticity.clone());
    }

    /**
     * Suppresses the 'cHRM' chunk from being output.
     */
    public void unsetChromaticity() {
        chromaticity = null;
        chromaticitySet = false;
    }

    /**
     * Returns true if a 'cHRM' chunk will be output.
     */
    public boolean isChromaticitySet() {
        return chromaticitySet;
    }

    // gAMA chunk

    private float gamma;
    private boolean gammaSet = false;

    /**
     * Sets the file gamma value for the image.
     *
     * <p> The 'gAMA' chunk will encode this information.
     */
    public void setGamma(float gamma) {
        this.gamma = gamma;
        gammaSet = true;
    }

    /**
     * Returns the file gamma value for the image.
     *
     * <p> If the file gamma has not previously been set, or has been
     * unset, an <code>IllegalStateException</code> will be thrown.
     *
     * @throws IllegalStateException if the gamma is not set.
     */
    public float getGamma() {
        if (!gammaSet) {
            throw new IllegalStateException(PropertyUtil.getString("PNGEncodeParam13"));
        }
        return gamma;
    }

    /**
     * Suppresses the 'gAMA' chunk from being output.
     */
    public void unsetGamma() {
        gammaSet = false;
    }

    /**
     * Returns true if a 'gAMA' chunk will be output.
     */
    public boolean isGammaSet() {
        return gammaSet;
    }

    // hIST chunk

    private int[] paletteHistogram = null;
    private boolean paletteHistogramSet = false;

    /**
     * Sets the palette histogram to be stored with this image.
     * The histogram consists of an array of integers, one per
     * palette entry.
     *
     * <p> The 'hIST' chunk will encode this information.
     */
    public void setPaletteHistogram(int[] paletteHistogram) {
        this.paletteHistogram = (int[])(paletteHistogram.clone());
        paletteHistogramSet = true;
    }

    /**
     * Returns the palette histogram to be stored with this image.
     *
     * <p> If the histogram has not previously been set, or has been
     * unset, an <code>IllegalStateException</code> will be thrown.
     *
     * @throws IllegalStateException if the histogram is not set.
     */
    public int[] getPaletteHistogram() {
        if (!paletteHistogramSet) {
            throw new IllegalStateException(PropertyUtil.getString("PNGEncodeParam14"));
        }
        return paletteHistogram;
    }

    /**
     * Suppresses the 'hIST' chunk from being output.
     */
    public void unsetPaletteHistogram() {
        paletteHistogram = null;
        paletteHistogramSet = false;
    }

    /**
     * Returns true if a 'hIST' chunk will be output.
     */
    public boolean isPaletteHistogramSet() {
        return paletteHistogramSet;
    }

    // iCCP chunk

    private byte[] ICCProfileData = null;
    private boolean ICCProfileDataSet = false;

    /**
     * Sets the ICC profile data to be stored with this image.
     * The profile is represented in raw binary form.
     *
     * <p> The 'iCCP' chunk will encode this information.
     */
    public void setICCProfileData(byte[] ICCProfileData) {
        this.ICCProfileData = (byte[])(ICCProfileData.clone());
        ICCProfileDataSet = true;
    }

    /**
     * Returns the ICC profile data to be stored with this image.
     *
     * <p> If the ICC profile has not previously been set, or has been
     * unset, an <code>IllegalStateException</code> will be thrown.
     *
     * @throws IllegalStateException if the ICC profile is not set.
     */
    public byte[] getICCProfileData() {
        if (!ICCProfileDataSet) {
            throw new IllegalStateException(PropertyUtil.getString("PNGEncodeParam15"));
        }
        return (byte[])(ICCProfileData.clone());
    }

    /**
     * Suppresses the 'iCCP' chunk from being output.
     */
    public void unsetICCProfileData() {
        ICCProfileData = null;
        ICCProfileDataSet = false;
    }

    /**
     * Returns true if a 'iCCP' chunk will be output.
     */
    public boolean isICCProfileDataSet() {
        return ICCProfileDataSet;
    }

    // pHYS chunk

    private int[] physicalDimension = null;
    private boolean physicalDimensionSet = false;

    /**
     * Sets the physical dimension information to be stored with this
     * image.  The physicalDimension parameter should be a 3-entry
     * array containing the number of pixels per unit in the X
     * direction, the number of pixels per unit in the Y direction,
     * and the unit specifier (0 = unknown, 1 = meters).
     *
     * <p> The 'pHYS' chunk will encode this information.
     */
    public void setPhysicalDimension(int[] physicalDimension) {
        this.physicalDimension = (int[])(physicalDimension.clone());
        physicalDimensionSet = true;
    }

    /**
     * A convenience method that calls the array version.
     */
    public void setPhysicalDimension(int xPixelsPerUnit,
                                     int yPixelsPerUnit,
                                     int unitSpecifier) {
        int[] pd = new int[3];
        pd[0] = xPixelsPerUnit;
        pd[1] = yPixelsPerUnit;
        pd[2] = unitSpecifier;
        
        setPhysicalDimension(pd);
    }

    /**
     * Returns the physical dimension information to be stored
     * with this image.
     *
     * <p> If the physical dimension information has not previously
     * been set, or has been unset, an
     * <code>IllegalStateException</code> will be thrown.
     *
     * @throws IllegalStateException if the physical dimension information
     *        is not set.
     */
    public int[] getPhysicalDimension() {
        if (!physicalDimensionSet) {
            throw new IllegalStateException(PropertyUtil.getString("PNGEncodeParam16"));
        }
        return (int[])(physicalDimension.clone());        
    }

    /**
     * Suppresses the 'pHYS' chunk from being output.
     */
    public void unsetPhysicalDimension() {
        physicalDimension = null;
        physicalDimensionSet = false;
    }

    /**
     * Returns true if a 'pHYS' chunk will be output.
     */
    public boolean isPhysicalDimensionSet() {
        return physicalDimensionSet;
    }

    // sPLT chunk

    private PNGSuggestedPaletteEntry[] suggestedPalette = null;
    private boolean suggestedPaletteSet = false;

    /**
     * Sets the suggested palette information to be stored with this
     * image.  The information is passed to this method as an array of
     * <code>PNGSuggestedPaletteEntry</code> objects.
     *
     * <p> The 'sPLT' chunk will encode this information.
     */
    public void setSuggestedPalette(PNGSuggestedPaletteEntry[] palette) {
        suggestedPalette = (PNGSuggestedPaletteEntry[])(palette.clone());
        suggestedPaletteSet = true;
    }

    /**
     * Returns the suggested palette information to be stored with this
     * image.
     *
     * <p> If the suggested palette information has not previously
     * been set, or has been unset, an
     * <code>IllegalStateException</code> will be thrown.
     *
     * @throws IllegalStateException if the suggested palette
     *        information is not set.
     */
    public PNGSuggestedPaletteEntry[] getSuggestedPalette() {
        if (!suggestedPaletteSet) {
            throw new IllegalStateException(PropertyUtil.getString("PNGEncodeParam17"));
        }
        return (PNGSuggestedPaletteEntry[])(suggestedPalette.clone());
    }

    /**
     * Suppresses the 'sPLT' chunk from being output.
     */
    public void unsetSuggestedPalette() {
        suggestedPalette = null;
        suggestedPaletteSet = false;
    }

    /**
     * Returns true if a 'sPLT' chunk will be output.
     */
    public boolean isSuggestedPaletteSet() {
        return suggestedPaletteSet;
    }

    // sBIT chunk

    private int[] significantBits = null;
    private boolean significantBitsSet = false;

    /**
     * Sets the number of significant bits for each band of the image.
     * 
     * <p> The number of entries in the <code>significantBits</code>
     * array must be equal to the number of output bands in the image:
     * 1 for a gray image, 2 for gray+alpha, 3 for index or truecolor,
     * and 4 for truecolor+alpha.
     *
     * <p> The 'sBIT' chunk will encode this information.
     */
    public void setSignificantBits(int[] significantBits) {
        this.significantBits = (int[])(significantBits.clone());
        significantBitsSet = true;
    }

    /**
     * Returns the number of significant bits for each band of the image.
     *
     * <p> If the significant bits values have not previously been
     * set, or have been unset, an <code>IllegalStateException</code>
     * will be thrown.
     *
     * @throws IllegalStateException if the significant bits values are
     *        not set.
     */
    public int[] getSignificantBits() {
        if (!significantBitsSet) {
            throw new IllegalStateException(PropertyUtil.getString("PNGEncodeParam18"));
        }
        return (int[])significantBits.clone();
    }

    /**
     * Suppresses the 'sBIT' chunk from being output.
     */
    public void unsetSignificantBits() {
        significantBits = null;
        significantBitsSet = false;
    }

    /**
     * Returns true if an 'sBIT' chunk will be output.
     */
    public boolean isSignificantBitsSet() {
        return significantBitsSet;
    }

    // sRGB chunk

    private int SRGBIntent;
    private boolean SRGBIntentSet = false;

    /**
     * Sets the sRGB rendering intent to be stored with this image.
     * The legal values are 0 = Perceptual, 1 = Relative Colorimetric,
     * 2 = Saturation, and 3 = Absolute Colorimetric.  Refer to the
     * PNG specification for information on these values.
     *
     * <p> The 'sRGB' chunk will encode this information.
     */
    public void setSRGBIntent(int SRGBIntent) {
        this.SRGBIntent = SRGBIntent;
        SRGBIntentSet = true;
    }

    /**
     * Returns the sRGB rendering intent to be stored with this image.
     *
     * <p> If the sRGB intent has not previously been set, or has been
     * unset, an <code>IllegalStateException</code> will be thrown.
     *
     * @throws IllegalStateException if the sRGB intent is not set.
     */
    public int getSRGBIntent() {
        if (!SRGBIntentSet) {
            throw new IllegalStateException(PropertyUtil.getString("PNGEncodeParam19"));
        }
        return SRGBIntent;
    }

    /**
     * Suppresses the 'sRGB' chunk from being output.
     */
    public void unsetSRGBIntent() {
        SRGBIntentSet = false;
    }

    /**
     * Returns true if an 'sRGB' chunk will be output.
     */
    public boolean isSRGBIntentSet() {
        return SRGBIntentSet;
    }

    // tEXt chunk

    private String[] text = null;
    private boolean textSet = false;

    /**
     * Sets the textual data to be stored in uncompressed form with this
     * image.  The data is passed to this method as an array of
     * <code>String</code>s.
     *
     * <p> The 'tEXt' chunk will encode this information.
     */
    public void setText(String[] text) {
        this.text = text;
        textSet = true;
    }

    /**
     * Returns the text strings to be stored in uncompressed form with this
     * image as an array of <code>String</code>s.
     *
     * <p> If the text strings have not previously been set, or have been
     * unset, an <code>IllegalStateException</code> will be thrown.
     *
     * @throws IllegalStateException if the text strings are not set.
     */
    public String[] getText() {
        if (!textSet) {
            throw new IllegalStateException(PropertyUtil.getString("PNGEncodeParam20"));
        }
        return text;
    }

    /**
     * Suppresses the 'tEXt' chunk from being output.
     */
    public void unsetText() {
        text = null;
        textSet = false;
    }

    /**
     * Returns true if a 'tEXt' chunk will be output.
     */
    public boolean isTextSet() {
        return textSet;
    }

    // tIME chunk

    private Date modificationTime;
    private boolean modificationTimeSet = false;

    /**
     * Sets the modification time, as a <code>Date</code>, to be
     * stored with this image.  The internal storage format will use
     * UTC regardless of how the <code>modificationTime</code>
     * parameter was created.
     *
     * <p> The 'tIME' chunk will encode this information.
     */
    public void setModificationTime(Date modificationTime) {
        this.modificationTime = modificationTime;
        modificationTimeSet = true;
    }

    /**
     * Returns the modification time to be stored with this image.
     *
     * <p> If the bit depth has not previously been set, or has been
     * unset, an <code>IllegalStateException</code> will be thrown.
     *
     * @throws IllegalStateException if the bit depth is not set.
     */
    public Date getModificationTime() {
        if (!modificationTimeSet) {
            throw new IllegalStateException(PropertyUtil.getString("PNGEncodeParam21"));
        }
        return modificationTime;
    }

    /**
     * Suppresses the 'tIME' chunk from being output.
     */
    public void unsetModificationTime() {
        modificationTime = null;
        modificationTimeSet = false;
    }

    /**
     * Returns true if a 'tIME' chunk will be output.
     */
    public boolean isModificationTimeSet() {
        return modificationTimeSet;
    }

    // tRNS chunk

    boolean transparencySet = false;

    /**
     * Suppresses the 'tRNS' chunk from being output.
     */
    public void unsetTransparency() {
        transparencySet = false;
    }

    /**
     * Returns true if a 'tRNS' chunk will be output.
     */
    public boolean isTransparencySet() {
        return transparencySet;
    }

    // zTXT chunk

    private String[] zText = null;
    private boolean zTextSet = false;

    /**
     * Sets the text strings to be stored in compressed form with this
     * image.  The data is passed to this method as an array of
     * <code>String</code>s.
     *
     * <p> The 'zTXt' chunk will encode this information.
     */
    public void setCompressedText(String[] text) {
        this.zText = text;
        zTextSet = true;
    }

    /**
     * Returns the text strings to be stored in compressed form with
     * this image as an array of <code>String</code>s.
     *
     * <p> If the compressed text strings have not previously been
     * set, or have been unset, an <code>IllegalStateException</code>
     * will be thrown.
     *
     * @throws IllegalStateException if the compressed text strings are
     *        not set.
     */
    public String[] getCompressedText() {
        if (!zTextSet) {
            throw new IllegalStateException(PropertyUtil.getString("PNGEncodeParam22"));
        }
        return zText;
    }

    /**
     * Suppresses the 'zTXt' chunk from being output.
     */
    public void unsetCompressedText() {
        zText = null;
        zTextSet = false;
    }

    /**
     * Returns true if a 'zTXT' chunk will be output.
     */
    public boolean isCompressedTextSet() {
        return zTextSet;
    }

    // Other chunk types
    
    Vector chunkType = new Vector();
    Vector chunkData = new Vector();

    /**
     * Adds a private chunk, in binary form, to the list of chunks to
     * be stored with this image.
     *
     * @param type a 4-character String giving the chunk type name.
     * @param data an array of <code>byte</code>s containing the
     *        chunk data.
     */
    public synchronized void addPrivateChunk(String type, byte[] data) {
        chunkType.add(type);
        chunkData.add((byte[])data.clone());
    }

    /**
     * Returns the number of private chunks to be written to the
     * output file.
     */
    public synchronized int getNumPrivateChunks() {
        return chunkType.size();
    }

    /**
     * Returns the type of the private chunk at a given index, as a
     * 4-character <code>String</code>.  The index must be smaller
     * than the return value of <code>getNumPrivateChunks</code>.
     */
    public synchronized String getPrivateChunkType(int index) {
        return (String)chunkType.elementAt(index);
    }

    /**
     * Returns the data associated of the private chunk at a given
     * index, as an array of <code>byte</code>s.  The index must be
     * smaller than the return value of
     * <code>getNumPrivateChunks</code>.
     */
    public synchronized byte[] getPrivateChunkData(int index) {
        return (byte[])chunkData.elementAt(index);
    }

    /**
     * Remove all private chunks associated with this parameter instance
     * whose 'safe-to-copy' bit is not set.  This may be advisable when
     * transcoding PNG images.
     */
    public synchronized void removeUnsafeToCopyPrivateChunks() {
        Vector newChunkType = new Vector();
        Vector newChunkData = new Vector();

        int len = getNumPrivateChunks();
        for (int i = 0; i < len; i++) {
            String type = getPrivateChunkType(i);
            char lastChar = type.charAt(3);
            if (lastChar >= 'a' && lastChar <= 'z') {
                newChunkType.add(type);
                newChunkData.add(getPrivateChunkData(i));
            }
        }

        chunkType = newChunkType;
        chunkData = newChunkData;
    }

    /**
     * Remove all private chunks associated with this parameter instance.
     */
    public synchronized void removeAllPrivateChunks() {
        chunkType = new Vector();
        chunkData = new Vector();
    }

    /**
     * An abs() function for use by the Paeth predictor.
     */
    private static final int abs(int x) {
        return (x < 0) ? -x : x;
    }

    /**
     * The Paeth predictor routine used in PNG encoding.  This routine
     * is included as a convenience to subclasses that override the
     * <code>filterRow</code> method.
     */
    public static final int paethPredictor(int a, int b, int c) {
        int p = a + b - c;
        int pa = abs(p - a);
        int pb = abs(p - b);
        int pc = abs(p - c);

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

    /**
     * Performs filtering on a row of an image.  This method may be
     * overridden in order to provide a custom algorithm for choosing
     * the filter type for a given row.
     *
     * <p> The method is supplied with the current and previous rows
     * of the image.  For the first row of the image, or of an
     * interlacing pass, the previous row array will be filled with
     * zeros as required by the PNG specification.
     *
     * <p> The method is also supplied with five scratch arrays.
     * These arrays may be used within the method for any purpose.
     * At method exit, the array at the index given by the return
     * value of the method should contain the filtered data.  The
     * return value will also be used as the filter type.
     *
     * <p> The default implementation of the method performs a trial
     * encoding with each of the filter types, and computes the sum of
     * absolute values of the differences between the raw bytes of the
     * current row and the predicted values.  The index of the filter
     * producing the smallest result is returned.
     *
     * <p> As an example, to perform only 'sub' filtering, this method
     * could be implemented (non-optimally) as follows:
     *
     * <pre>
     * for (int i = bytesPerPixel; i < bytesPerRow + bytesPerPixel; i++) {
     *     int curr = currRow[i] & 0xff;
     *     int left = currRow[i - bytesPerPixel] & 0xff;
     *     scratchRow[PNG_FILTER_SUB][i] = (byte)(curr - left);
     * }
     * return PNG_FILTER_SUB;
     * </pre>
     *
     * @param currRow The current row as an array of <code>byte</code>s
     *        of length at least <code>bytesPerRow + bytesPerPixel</code>.
     *        The pixel data starts at index <code>bytesPerPixel</code>;
     *        the initial <code>bytesPerPixel</code> bytes are zero.
     * @param prevRow The current row as an array of <code>byte</code>s
     *        The pixel data starts at index <code>bytesPerPixel</code>;
     *        the initial <code>bytesPerPixel</code> bytes are zero.
     * @param scratchRows An array of 5 <code>byte</code> arrays of
     *        length at least <code>bytesPerRow +
     *        bytesPerPixel</code>, useable to hold temporary results.
     *        The filtered row will be returned as one of the entries
     *        of this array.  The returned filtered data should start
     *        at index <code>bytesPerPixel</code>; The initial
     *        <code>bytesPerPixel</code> bytes are not used.
     * @param bytesPerRow The number of bytes in the image row.
     *        This value will always be greater than 0.
     * @param bytesPerPixel The number of bytes representing a single
     *        pixel, rounded up to an integer.  This is the 'bpp' parameter
     *        described in the PNG specification.
     *
     * @return The filter type to be used.  The entry of
     *         <code>scratchRows[]</code> at this index holds the
     *         filtered data.  */
    public int filterRow(byte[] currRow,
                         byte[] prevRow,
                         byte[][] scratchRows,
                         int bytesPerRow,
                         int bytesPerPixel) {

        int [] badness = {0, 0, 0, 0, 0};
        int curr, left, up, upleft, diff;
        int pa, pb, pc;
        for (int i = bytesPerPixel; i < bytesPerRow + bytesPerPixel; i++) {
            curr   = currRow[i] & 0xff;
            left   = currRow[i - bytesPerPixel] & 0xff;
            up     = prevRow[i] & 0xff;
            upleft = prevRow[i - bytesPerPixel] & 0xff;
                
            // no filter
            badness[0] += curr;

            // sub filter
            diff = curr - left;
            scratchRows[1][i]  = (byte)diff;
            badness    [1]    +=   (diff>0)?diff:-diff;

            // up filter
            diff = curr - up;
            scratchRows[2][i]  = (byte)diff;
            badness    [2]    +=   (diff>=0)?diff:-diff;
                
            // average filter
            diff = curr - ((left+up)>>1);
            scratchRows[3][i]  = (byte)diff;
            badness    [3]    +=   (diff>=0)?diff:-diff;
                
            // paeth filter

            // Original code much simplier but doesn't take full
            // advantage of relationship between pa/b/c and
            // information gleaned in abs operations.
            /// pa = up  -upleft;
            /// pb = left-upleft;
            /// pc = pa+pb;
            /// pa = abs(pa);
            /// pb = abs(pb);
            /// pc = abs(pc);
            /// if ((pa <= pb) && (pa <= pc))
            ///   diff = curr-left;
            /// else if (pb <= pc)
            ///   diff = curr-up;
            /// else
            ///   diff = curr-upleft;

            pa = up  -upleft;
            pb = left-upleft;
            if (pa<0) {
              if (pb<0) {
                // both pa & pb neg so pc is always greater than or
                // equal to pa or pb;
                if (pa >= pb) // since pa & pb neg check sense is reversed.
                  diff = curr-left;
                else
                  diff = curr-up;
              } else {
                // pa neg pb pos so we must compute pc...
                pc = pa+pb;
                pa=-pa;
                if (pa <= pb)     // pc is positive and less than pb
                  if (pa <= pc)
                    diff = curr-left;
                  else
                    diff = curr-upleft;
                else 
                  // pc is negative and less than or equal to pa,
                  // but since pa is greater than pb this isn't an issue...
                  if (pb <= -pc)
                    diff = curr-up;
                  else
                    diff = curr-upleft;
              }
            } else {
              if (pb<0) {
                pb =-pb; // make it positive...
                if (pa <= pb) {  
                  // pc would be negative and less than or equal to pb
                  pc = pb-pa;
                  if (pa <= pc)
                    diff = curr-left;
                  else if (pb == pc) 
                    // if pa is zero then pc==pb otherwise
                    // pc must be less than pb.
                    diff = curr-up;
                  else 
                    diff = curr-upleft;
                } else { 
                  // pc would be positive and less than pa.
                  pc = pa-pb;
                  if (pb <= pc)
                    diff = curr-up;
                  else
                    diff = curr-upleft;
                }
              } else {
                // both pos so pa+pb is always greater than pa/pb
                if (pa <= pb)
                  diff = curr-left;
                else
                  diff = curr-up;
              }
            }
            scratchRows[4][i]  = (byte)diff;
            badness    [4]    +=   (diff>=0)?diff:-diff;
        }
        int filterType = 0;
        int minBadness = badness[0];
        
        for (int i = 1; i < 5; i++) {
            if (badness[i] < minBadness) {
                minBadness = badness[i];
                filterType = i;
            }
        }

        if (filterType == 0) {
            System.arraycopy(currRow, bytesPerPixel,
                             scratchRows[0], bytesPerPixel,
                             bytesPerRow);
        }
        
        return filterType;
    }
}
