protected void writeHeader()    {        int startPos;        startPos = bytePos = writeInt4( 13, bytePos );        bytePos = writeBytes( IHDR, bytePos );        width = image.getWidth( null );        height = image.getHeight( null );        bytePos = writeInt4( width, bytePos );        bytePos = writeInt4( height, bytePos );        bytePos = writeByte( 8, bytePos ); // bit depth        if (bytesPerPixel != 1)        {            bytePos = writeByte( (encodeAlpha) ? 6 : 2, bytePos ); // direct model        }        else        {            bytePos = writeByte( 3, bytePos ); // indexed        }        bytePos = writeByte( 0, bytePos ); // compression method        bytePos = writeByte( 0, bytePos ); // filter method        bytePos = writeByte( 0, bytePos ); // no interlace        crc.reset();        crc.update( pngBytes, startPos, bytePos-startPos );        crcValue = crc.getValue();        bytePos = writeInt4( (int) crcValue, bytePos );    }    protected void writePalette( IndexColorModel icm )    {        byte[] redPal = new byte[256];        byte[] greenPal = new byte[256];        byte[] bluePal = new byte[256];        byte[] allPal = new byte[768];        int i;        icm.getReds( redPal );        icm.getGreens( greenPal );        icm.getBlues( bluePal );        for (i=0; i<256; i++)        {            allPal[i*3  ] = redPal[i];            allPal[i*3+1] = greenPal[i];            allPal[i*3+2] = bluePal[i];        }        bytePos = writeInt4( 768, bytePos );        bytePos = writeBytes( PLTE, bytePos );        crc.reset();        crc.update( PLTE );        bytePos = writeBytes( allPal, bytePos );        crc.update( allPal );        crcValue = crc.getValue();        bytePos = writeInt4( (int) crcValue, bytePos );    }    /**     * 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)        int readPos;            // position from which source pixels are read        byte[] compressedLines; // the resultant compressed lines        int nCompressed;        // how big is the compressed area?        byte[] pixels;          // storage area for byte-sized pixels        int[] iPixels;          // storage area for int-sized pixels		short[] sPixels;		// for Win 2000/ME ushort pixels		final int type = image.getType();		// TYPE_INT_RGB        = 1		// TYPE_INT_ARGB       = 2		// TYPE_INT_ARGB_PRE   = 3		// TYPE_INT_BGR        = 4		// TYPE_3BYTE_BGR      = 5		// TYPE_4BYTE_ABGR     = 6		// TYPE_4BYTE_ABGR_PRE = 7		// TYPE_BYTE_GRAY      = 10		// TYPE_BYTE_BINARY    = 12		// TYPE_BYTE_INDEXED   = 13		// TYPE_USHORT_GRAY    = 11		// TYPE_USHORT_565_RGB = 8		// TYPE_USHORT_555_RGB = 9		// TYPE_CUSTOM         = 0.        Deflater scrunch = new Deflater( compressionLevel );        ByteArrayOutputStream outBytes =             new ByteArrayOutputStream(1024);                    DeflaterOutputStream compBytes =            new DeflaterOutputStream( outBytes, scrunch );        if (bytesPerPixel == 1)        {            writePalette( (IndexColorModel) image.getColorModel() );        }        try        {            while (rowsLeft > 0)            {                nRows = Math.min( 32767 / (width*(bytesPerPixel+1)), rowsLeft );                nRows = Math.max( nRows, 1 );                /*                 * Create a data chunk. scanLines adds "nRows" for                 * the filter bytes.                 */                scanLines = new byte[width * nRows * bytesPerPixel +  nRows];                if (filter == FILTER_SUB)                {                    leftBytes = new byte[16];                }                if (filter == FILTER_UP)                {                    priorRow = new byte[width*bytesPerPixel];                }				final Object data =					wRaster.getDataElements( 0, startRow, width, nRows, null );                pixels = null;				iPixels = null;				sPixels = null;				if (tType == DataBuffer.TYPE_BYTE)                {                    pixels = (byte[]) data;                }                else if (tType == DataBuffer.TYPE_INT)                {                    iPixels = (int[]) data;				}				else if (tType == DataBuffer.TYPE_USHORT)				{					sPixels = (short[]) data;				}                scanPos = 0;                readPos = 0;                startPos = 1;                for (int i=0; i<width*nRows; i++)                {                    if (i % width == 0)                    {                        scanLines[scanPos++] = (byte) filter;                         startPos = scanPos;                    }                    if (bytesPerPixel == 1)	// assume TYPE_BYTE, indexed                    {                        scanLines[scanPos++] = pixels[readPos++];                    }                    else if (tType == DataBuffer.TYPE_BYTE)                    {                        scanLines[scanPos++] = pixels[readPos++];                        scanLines[scanPos++] = pixels[readPos++];                        scanLines[scanPos++] = pixels[readPos++];                        if (encodeAlpha)                        {                            scanLines[scanPos++] = pixels[readPos++];                        }                        else                        {                            readPos++;                        }                    }					else if (tType == DataBuffer.TYPE_USHORT)					{						short pxl = sPixels[readPos++];						if (type == BufferedImage.TYPE_USHORT_565_RGB) {							scanLines[scanPos++] = (byte) ((pxl >> 8) & 0xf8);							scanLines[scanPos++] = (byte) ((pxl >> 2) & 0xfc);						} else {                // assume USHORT_555_RGB							scanLines[scanPos++] = (byte) ((pxl >> 7) & 0xf8);							scanLines[scanPos++] = (byte) ((pxl >> 2) & 0xf8);						}						scanLines[scanPos++] = (byte) ((pxl << 3) & 0xf8);					}					else      // assume tType INT and type RGB or ARGB					{						int pxl = iPixels[readPos++];						scanLines[scanPos++] = (byte) ((pxl >> 16) & 0xff);						scanLines[scanPos++] = (byte) ((pxl >>  8) & 0xff);						scanLines[scanPos++] = (byte) ((pxl      ) & 0xff);						if (encodeAlpha) {							scanLines[scanPos++] = (byte) ((pxl >> 24) & 0xff);						}					}                    if ((i % width == width-1) && (filter != FILTER_NONE))                    {                        if (filter == FILTER_SUB)                        {                            filterSub( scanLines, startPos, width );                        }                        if (filter == FILTER_UP)                        {                            filterUp( scanLines, startPos, 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;            crc.reset();            bytePos = writeInt4( nCompressed, bytePos );            bytePos = writeBytes( IDAT, bytePos );            crc.update( IDAT );            bytePos = writeBytes( compressedLines, nCompressed, bytePos );            crc.update( compressedLines, 0, nCompressed );            crcValue = crc.getValue();            bytePos = writeInt4( (int) crcValue, bytePos );            scrunch.finish();            return true;        }        catch (IOException e)        {            System.err.println( e.toString());            return false;        }    }}