pngencoderb.java

PngEncoder - convert a Java Image to PNG PngEncoderB - convert a Java BufferedImage to PNG

    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;
        }
    }

}