package com.keypoint;

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

/**
 * PngEncoder takes a Java Image object and creates a byte string which can be
 * saved as a PNG file.  The Image is presumed to use the DirectColorModel.
 *
 * <p>Thanks to Jay Denny at KeyPoint Software
 *    http://www.keypoint.com/
 * who let me develop this code on company time.</p>
 *
 * <p>You may contact me with (probably very-much-needed) improvements,
 * comments, and bug fixes at:</p>
 *
 *   <p><code>david@catcode.com</code></p>
 *
 * <p>This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.</p>
 *
 * <p>This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.</p>
 *
 * <p>You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301,
 * USA. A copy of the GNU LGPL may be found at
 * <code>http://www.gnu.org/copyleft/lesser.html</code></p>
 *
 * @author J. David Eisenberg
 * @version 1.5, 19 Oct 2003
 *
 * CHANGES:
 * --------
 * 19-Nov-2002 : CODING STYLE CHANGES ONLY (by David Gilbert for Object
 *               Refinery Limited);
 * 19-Sep-2003 : Fix for platforms using EBCDIC (contributed by Paulo Soares);
 * 19-Oct-2003 : Change private fields to protected fields so that
 *               PngEncoderB can inherit them (JDE)
 *               Fixed bug with calculation of nRows
 * 15-Aug-2008 : Added scrunch.end() in writeImageData() method - see
 *               JFreeChart bug report 2037930 (David Gilbert);
 */

public class PngEncoder {

    /** Constant specifying that alpha channel should be encoded. */
    public static final boolean ENCODE_ALPHA = true;

    /** Constant specifying that alpha channel should not be encoded. */
    public static final boolean NO_ALPHA = false;

    /** Constants for filter (NONE). */
    public static final int FILTER_NONE = 0;

    /** Constants for filter (SUB). */
    public static final int FILTER_SUB = 1;

    /** Constants for filter (UP). */
    public static final int FILTER_UP = 2;

    /** Constants for filter (LAST). */
    public static final int FILTER_LAST = 2;

    /** IHDR tag. */
    protected static final byte[] IHDR = {73, 72, 68, 82};

    /** IDAT tag. */
    protected static final byte[] IDAT = {73, 68, 65, 84};

    /** IEND tag. */
    protected static final byte[] IEND = {73, 69, 78, 68};

    /** PHYS tag. */
    protected static final byte[] PHYS = {(byte)'p', (byte)'H', (byte)'Y',
        (byte)'s'};

    /** The png bytes. */
    protected byte[] pngBytes;

    /** The prior row. */
    protected byte[] priorRow;

    /** The left bytes. */
    protected byte[] leftBytes;

    /** The image. */
    protected Image image;

    /** The width. */
    protected int width;

    /** The height. */
    protected int height;

    /** The byte position. */
    protected int bytePos;

    /** The maximum position. */
    protected int maxPos;

    /** CRC. */
    protected CRC32 crc = new CRC32();

    /** The CRC value. */
    protected long crcValue;

    /** Encode alpha? */
    protected boolean encodeAlpha;

    /** The filter type. */
    protected int filter;

    /** The bytes-per-pixel. */
    protected int bytesPerPixel;

    /** The physical pixel dimension : number of pixels per inch on the X axis. */
    private int xDpi = 0;

    /** The physical pixel dimension : number of pixels per inch on the Y axis. */
    private int yDpi = 0;

    /** Used for conversion of DPI to Pixels per Meter. */
    static private float INCH_IN_METER_UNIT = 0.0254f;

    /**
     * The compression level (1 = best speed, 9 = best compression,
     * 0 = no compression).
     */
    protected int compressionLevel;

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

    /**
     * Class constructor specifying Image to encode, with no alpha channel
     * encoding.
     *
     * @param image A Java Image object which uses the DirectColorModel
     * @see java.awt.Image
     */
    public PngEncoder(Image image) {
        this(image, false, FILTER_NONE, 0);
    }

    /**
     * Class constructor specifying Image to encode, and whether to encode
     * alpha.
     *
     * @param image A Java Image object which uses the DirectColorModel
     * @param encodeAlpha Encode the alpha channel? false=no; true=yes
     * @see java.awt.Image
     */
    public PngEncoder(Image image, boolean encodeAlpha) {
        this(image, encodeAlpha, FILTER_NONE, 0);
    }

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


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

    /**
     * Set the image to be encoded.
     *
     * @param image A Java Image object which uses the DirectColorModel
     * @see java.awt.Image
     * @see java.awt.image.DirectColorModel
     */
    public void setImage(Image image) {
        this.image = image;
        this.pngBytes = null;
    }

    /**
     * Returns the image to be encoded.
     *
     * @return The image.
     */
    public Image getImage() {
      return this.image;
    }

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

        if (this.image == null) {
            return null;
        }
        this.width = this.image.getWidth(null);
        this.height = this.image.getHeight(null);

        /*
         * start with an array that is big enough to hold all the pixels
         * (plus filter bytes), and an extra 200 bytes for header info
         */
        this.pngBytes = new byte[((this.width + 1) * this.height * 3) + 200];

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

        this.bytePos = writeBytes(pngIdBytes, 0);
        //hdrPos = bytePos;
        writeHeader();
        writeResolution();
        //dataPos = bytePos;
        if (writeImageData()) {
            writeEnd();
            this.pngBytes = resizeByteArray(this.pngBytes, this.maxPos);
        }
        else {
            this.pngBytes = null;
        }
        return this.pngBytes;
    }

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

    /**
     * Set the alpha encoding on or off.
     *
     * @param encodeAlpha  false=no, true=yes
     */
    public void setEncodeAlpha(boolean encodeAlpha) {
        this.encodeAlpha = encodeAlpha;
    }

    /**
     * Retrieve alpha encoding status.
     *
     * @return boolean false=no, true=yes
     */
    public boolean getEncodeAlpha() {
        return this.encodeAlpha;
    }

    /**
     * Set the filter to use.
     *
     * @param whichFilter from constant list
     */
    public void setFilter(int whichFilter) {
        this.filter = FILTER_NONE;
        if (whichFilter <= FILTER_LAST) {
            this.filter = whichFilter;
        }
    }

    /**
     * Retrieve filtering scheme.
     *
     * @return int (see constant list)
     */
    public int getFilter() {
        return this.filter;
    }

    /**
     * Set the compression level to use.
     *
     * @param level the compression level (1 = best speed, 9 = best compression,
     *        0 = no compression)
     */
    public void setCompressionLevel(int level) {
        if (level >= 0 && level <= 9) {
            this.compressionLevel = level;
        }
    }

    /**
     * Retrieve compression level.
     *
     * @return int (1 = best speed, 9 = best compression, 0 = no compression)
     */
    public int getCompressionLevel() {
        return this.compressionLevel;
    }

    /**
     * Increase or decrease the length of a byte array.
     *
     * @param array The original array.
     * @param newLength The length you wish the new array to have.
     * @return Array of newly desired length. If shorter than the
     *         original, the trailing elements are truncated.
     */
    protected byte[] resizeByteArray(byte[] array, int newLength) {
        byte[]  newArray = new byte[newLength];
        int     oldLength = array.length;

        System.arraycopy(array, 0, newArray, 0, Math.min(oldLength, newLength));
        return newArray;
    }

    /**
     * Write an array of bytes into the pngBytes array.
     * Note: This routine has the side effect of updating
     * maxPos, the largest element written in the array.
     * The array is resized by 1000 bytes or the length
     * of the data to be written, whichever is larger.
     *
     * @param data The data to be written into pngBytes.
     * @param offset The starting point to write to.
     * @return The next place to be written to in the pngBytes array.
     */
    protected int writeBytes(byte[] data, int offset) {
        this.maxPos = Math.max(this.maxPos, offset + data.length);
        if (data.length + offset > this.pngBytes.length) {
            this.pngBytes = resizeByteArray(this.pngBytes, this.pngBytes.length
                    + Math.max(1000, data.length));
        }
        System.arraycopy(data, 0, this.pngBytes, offset, data.length);
        return offset + data.length;
    }

    /**
     * Write an array of bytes into the pngBytes array, specifying number of
     * bytes to write. Note: This routine has the side effect of updating
     * maxPos, the largest element written in the array.
     * The array is resized by 1000 bytes or the length
     * of the data to be written, whichever is larger.
     *
     * @param data The data to be written into pngBytes.
     * @param nBytes The number of bytes to be written.
     * @param offset The starting point to write to.
     * @return The next place to be written to in the pngBytes array.
     */
    protected int writeBytes(byte[] data, int nBytes, int offset) {
        this.maxPos = Math.max(this.maxPos, offset + nBytes);
        if (nBytes + offset > this.pngBytes.length) {
            this.pngBytes = resizeByteArray(this.pngBytes, this.pngBytes.length
                    + Math.max(1000, nBytes));
        }
        System.arraycopy(data, 0, this.pngBytes, offset, nBytes);
        return offset + nBytes;
    }

    /**
     * Write a two-byte integer into the pngBytes array at a given position.
     *
     * @param n The integer to be written into pngBytes.
     * @param offset The starting point to write to.
     * @return The next place to be written to in the pngBytes array.
     */
    protected int writeInt2(int n, int offset) {
        byte[] temp = {(byte) ((n >> 8) & 0xff), (byte) (n & 0xff)};
        return writeBytes(temp, offset);
    }

    /**
     * Write a four-byte integer into the pngBytes array at a given position.
     *
     * @param n The integer to be written into pngBytes.
     * @param offset The starting point to write to.
     * @return The next place to be written to in the pngBytes array.
     */
    protected int writeInt4(int n, int offset) {
        byte[] temp = {(byte) ((n >> 24) & 0xff),
                       (byte) ((n >> 16) & 0xff),
                       (byte) ((n >> 8) & 0xff),
                       (byte) (n & 0xff)};
        return writeBytes(temp, offset);
    }

    /**
     * Write a single byte into the pngBytes array at a given position.
     *
     * @param b The integer to be written into pngBytes.
     * @param offset The starting point to write to.
     * @return The next place to be written to in the pngBytes array.
     */
    protected int writeByte(int b, int offset) {
        byte[] temp = {(byte) b};
        return writeBytes(temp, offset);
    }

    /**
     * Write a PNG "IHDR" chunk into the pngBytes array.
     */
    protected void writeHeader() {

        int startPos = this.bytePos = writeInt4(13, this.bytePos);
        this.bytePos = writeBytes(IHDR, this.bytePos);
        this.width = this.image.getWidth(null);
        this.height = this.image.getHeight(null);
        this.bytePos = writeInt4(this.width, this.bytePos);
        this.bytePos = writeInt4(this.height, this.bytePos);
        this.bytePos = writeByte(8, this.bytePos); // bit depth
        this.bytePos = writeByte((this.encodeAlpha) ? 6 : 2, this.bytePos);
            // direct model
        this.bytePos = writeByte(0, this.bytePos); // compression method
        this.bytePos = writeByte(0, this.bytePos); // filter method
        this.bytePos = writeByte(0, this.bytePos); // no interlace
        this.crc.reset();
        this.crc.update(this.pngBytes, startPos, this.bytePos - startPos);
        this.crcValue = this.crc.getValue();
        this.bytePos = writeInt4((int) this.crcValue, this.bytePos);
    }

    /**
     * Perform "sub" filtering on the given row.
     * Uses temporary array leftBytes to store the original values
     * of the previous pixels.  The array is 16 bytes long, which
     * will easily hold two-byte samples plus two-byte alpha.
     *
     * @param pixels The array holding the scan lines being built
     * @param startPos Starting position within pixels of bytes to be filtered.
     * @param width Width of a scanline in pixels.
     */
    protected void filterSub(byte[] pixels, int startPos, int width) {
        int offset = this.bytesPerPixel;
        int actualStart = startPos + offset;
        int nBytes = width * this.bytesPerPixel;
        int leftInsert = offset;
        int leftExtract = 0;

        for (int i = actualStart; i < startPos + nBytes; i++) {
            this.leftBytes[leftInsert] =  pixels[i];
            pixels[i] = (byte) ((pixels[i] - this.leftBytes[leftExtract])
                     % 256);
            leftInsert = (leftInsert + 1) % 0x0f;
            leftExtract = (leftExtract + 1) % 0x0f;
        }
    }

    /**
     * Perform "up" filtering on the given row.
     * Side effect: refills the prior row with current row
     *
     * @param pixels The array holding the scan lines being built
     * @param startPos Starting position within pixels of bytes to be filtered.
     * @param width Width of a scanline in pixels.
     */
    protected void filterUp(byte[] pixels, int startPos, int width) {

        final int nBytes = width * this.bytesPerPixel;

        for (int i = 0; i < nBytes; i++) {
            final byte currentByte = pixels[startPos + i];
            pixels[startPos + i] = (byte) ((pixels[startPos  + i]
                    - this.priorRow[i]) % 256);
            this.priorRow[i] = currentByte;
        }
    }

    /**
     * Write the image data into the pngBytes array.
     * This will write one or more PNG "IDAT" chunks. In order
     * to conserve memory, this method grabs as many rows as will
     * fit into 32K bytes, or the whole image; whichever is less.
     *
     *
     * @return true if no errors; false if error grabbing pixels
     */
    protected boolean writeImageData() {
        int rowsLeft = this.height;  // number of rows remaining to write
        int startRow = 0;       // starting row to process this time through
        int nRows;              // how many rows to grab at a time

        byte[] scanLines;       // the scan lines to be compressed
        int scanPos;            // where we are in the scan lines
        int startPos;           // where this line's actual pixels start (used
                                // for filtering)

        byte[] compressedLines; // the resultant compressed lines
        int nCompressed;        // how big is the compressed area?

        //int depth;              // color depth ( handle only 8 or 32 )

        PixelGrabber pg;

        this.bytesPerPixel = (this.encodeAlpha) ? 4 : 3;

        Deflater scrunch = new Deflater(this.compressionLevel);
        ByteArrayOutputStream outBytes = new ByteArrayOutputStream(1024);

        DeflaterOutputStream compBytes = new DeflaterOutputStream(outBytes,
                scrunch);
        try {
            while (rowsLeft > 0) {
                nRows = Math.min(32767 / (this.width
                        * (this.bytesPerPixel + 1)), rowsLeft);
                nRows = Math.max(nRows, 1);

                int[] pixels = new int[this.width * nRows];

                pg = new PixelGrabber(this.image, 0, startRow,
                        this.width, nRows, pixels, 0, this.width);
                try {
                    pg.grabPixels();
                }
                catch (Exception e) {
                    System.err.println("interrupted waiting for pixels!");
                    return false;
                }
                if ((pg.getStatus() & ImageObserver.ABORT) != 0) {
                    System.err.println("image fetch aborted or errored");
                    return false;
                }

                /*
                 * Create a data chunk. scanLines adds "nRows" for
                 * the filter bytes.
                 */
                scanLines = new byte[this.width * nRows * this.bytesPerPixel
                                     + nRows];

                if (this.filter == FILTER_SUB) {
                    this.leftBytes = new byte[16];
                }
                if (this.filter == FILTER_UP) {
                    this.priorRow = new byte[this.width * this.bytesPerPixel];
                }

                scanPos = 0;
                startPos = 1;
                for (int i = 0; i < this.width * nRows; i++) {
                    if (i % this.width == 0) {
                        scanLines[scanPos++] = (byte) this.filter;
                        startPos = scanPos;
                    }
                    scanLines[scanPos++] = (byte) ((pixels[i] >> 16) & 0xff);
                    scanLines[scanPos++] = (byte) ((pixels[i] >>  8) & 0xff);
                    scanLines[scanPos++] = (byte) ((pixels[i]) & 0xff);
                    if (this.encodeAlpha) {
                        scanLines[scanPos++] = (byte) ((pixels[i] >> 24)
                                & 0xff);
                    }
                    if ((i % this.width == this.width - 1)
                            && (this.filter != FILTER_NONE)) {
                        if (this.filter == FILTER_SUB) {
                            filterSub(scanLines, startPos, this.width);
                        }
                        if (this.filter == FILTER_UP) {
                            filterUp(scanLines, startPos, this.width);
                        }
                    }
                }

                /*
                 * Write these lines to the output area
                 */
                compBytes.write(scanLines, 0, scanPos);

                startRow += nRows;
                rowsLeft -= nRows;
            }
            compBytes.close();

            /*
             * Write the compressed bytes
             */
            compressedLines = outBytes.toByteArray();
            nCompressed = compressedLines.length;

            this.crc.reset();
            this.bytePos = writeInt4(nCompressed, this.bytePos);
            this.bytePos = writeBytes(IDAT, this.bytePos);
            this.crc.update(IDAT);
            this.bytePos = writeBytes(compressedLines, nCompressed,
                    this.bytePos);
            this.crc.update(compressedLines, 0, nCompressed);

            this.crcValue = this.crc.getValue();
            this.bytePos = writeInt4((int) this.crcValue, this.bytePos);
            scrunch.finish();
            scrunch.end();
            return true;
        }
        catch (IOException e) {
            System.err.println(e.toString());
            return false;
        }
    }

    /**
     * Write a PNG "IEND" chunk into the pngBytes array.
     */
    protected void writeEnd() {
        this.bytePos = writeInt4(0, this.bytePos);
        this.bytePos = writeBytes(IEND, this.bytePos);
        this.crc.reset();
        this.crc.update(IEND);
        this.crcValue = this.crc.getValue();
        this.bytePos = writeInt4((int) this.crcValue, this.bytePos);
    }


    /**
     * Set the DPI for the X axis.
     *
     * @param xDpi  The number of dots per inch
     */
    public void setXDpi(int xDpi) {
        this.xDpi = Math.round(xDpi / INCH_IN_METER_UNIT);

    }

    /**
     * Get the DPI for the X axis.
     *
     * @return The number of dots per inch
     */
    public int getXDpi() {
        return Math.round(this.xDpi * INCH_IN_METER_UNIT);
    }

    /**
     * Set the DPI for the Y axis.
     *
     * @param yDpi  The number of dots per inch
     */
    public void setYDpi(int yDpi) {
        this.yDpi = Math.round(yDpi / INCH_IN_METER_UNIT);
    }

    /**
     * Get the DPI for the Y axis.
     *
     * @return The number of dots per inch
     */
    public int getYDpi() {
        return Math.round(this.yDpi * INCH_IN_METER_UNIT);
    }

    /**
     * Set the DPI resolution.
     *
     * @param xDpi  The number of dots per inch for the X axis.
     * @param yDpi  The number of dots per inch for the Y axis.
     */
    public void setDpi(int xDpi, int yDpi) {
        this.xDpi = Math.round(xDpi / INCH_IN_METER_UNIT);
        this.yDpi = Math.round(yDpi / INCH_IN_METER_UNIT);
    }

    /**
     * Write a PNG "pHYs" chunk into the pngBytes array.
     */
    protected void writeResolution() {
        if (this.xDpi > 0 && this.yDpi > 0) {

            final int startPos = this.bytePos = writeInt4(9, this.bytePos);
            this.bytePos = writeBytes(PHYS, this.bytePos);
            this.bytePos = writeInt4(this.xDpi, this.bytePos);
            this.bytePos = writeInt4(this.yDpi, this.bytePos);
            this.bytePos = writeByte(1, this.bytePos); // unit is the meter.

            this.crc.reset();
            this.crc.update(this.pngBytes, startPos, this.bytePos - startPos);
            this.crcValue = this.crc.getValue();
            this.bytePos = writeInt4((int) this.crcValue, this.bytePos);
        }
    }
}