/** * 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. * * Thanks to Jay Denny at KeyPoint Software * http://www.keypoint.com/ * who let me develop this code on company time. * * You may contact me with (probably very-mUCh-needed) improvements, * comments, and bug fixes at: * * david@catcode.com * * 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. * * 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. * * 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., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA * A copy of the GNU LGPL may be found at * http://www.gnu.org/copyleft/lesser.Html, * * @author J. David Eisenberg * @version 1.4, 31 March 2000 */
public class PngEncoder extends Object { /** 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 filters */ public static final int FILTER_NONE = 0; public static final int FILTER_SUB = 1; public static final int FILTER_UP = 2; public static final int FILTER_LAST = 2;
protected byte[] pngBytes; protected byte[] priorRow; protected byte[] leftBytes; protected Image image; protected int width, height; protected int bytePos, maXPos; protected int hdrPos, dataPos, endPos; protected CRC32 crc = new CRC32(); protected long crcValue; protected boolean encodeAlpha; protected int filter; protected int bytesPerPixel; 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 * @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; pngBytes = null; }
/** * 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 }; int i;
/* * start with an array that is big enough to hold all the pixels * (plus filter bytes), and an extra 200 bytes for header info */ pngBytes = new byte[((width+1) * height * 3) + 200];
/* * keep track of largest byte written to the array */ maxPos = 0;
/** * 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( encodeAlpha ); }
/** * Set the alpha encoding on or off. * * @param encodeAlpha false=no, true=yes */ public void setEncodeAlpha( boolean encodeAlpha ) { this.encodeAlpha = 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 filter; }
/** * Set the compression level to use * * @param level 0 through 9 */ public void setCompressionLevel( int level ) { if ( level >= 0 && level <= 9) { this.compressionLevel = level; } }
/** * Retrieve compression level * * @return int in range 0-9 */ public int getCompressionLevel() { return 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;
/** * 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 ) { maxPos = Math.max( maxPos, offset + data.length ); if (data.length + offset > pngBytes.length) { pngBytes = resizeByteArray( pngBytes, pngBytes.length + Math.max( 1000, data.length ) ); } System.arraycopy( data, 0, 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 ) { maxPos = Math.max( maxPos, offset + nBytes ); if (nBytes + offset > pngBytes.length) { pngBytes = resizeByteArray( pngBytes, pngBytes.length + Math.max( 1000, nBytes ) ); } System.arraycopy( data, 0, 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 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 writeByte( int b, int offset ) { byte[] temp = { (byte) b }; return writeBytes( temp, offset ); }
/** * Write a string into the pngBytes array at a given position. * This uses the getBytes method, so the encoding used will * be its default. * * @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. * @see java.lang.String#getBytes() */ protected int writeString( String s, int offset ) { return writeBytes( s.getBytes(), offset ); }
/** * Write a PNG "IHDR" chunk into the pngBytes array. */ protected void writeHeader() { int startPos;
/** * 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 i; int offset = bytesPerPixel; int actualStart = startPos + offset; int nBytes = width * bytesPerPixel; int leftInsert = offset; int leftExtract = 0; byte current_byte;
/** * 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 ) { int i, nBytes; byte current_byte;
/** * 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 = 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;
bytesPerPixel = (encodeAlpha) ? 4 : 3;
Deflater scrunch = new Deflater( compressionLevel ); ByteArrayOutputStream outBytes = new ByteArrayOutputStream(1024);
