content: 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);
          }
      }
  }
  