// Flush the current scanline.
public void FlushScanline()
{
byte[] temp;
int x, posn, width;
int bpp = bytesPerPixel;
int bytesPerLine = this.bytesPerLine;
// Filter the scanline. We use a fairly simple approach,
// using no filter for indexed images and the "Paeth"
// filter for RGB images, as recommended by RFC-2083.
// It is possible to dynamically adjust the filter to
// match the scanline, but we don't do that at the moment.
if (usePaeth && y > 0 && bytesPerLine > 0)
{
// Apply the "Paeth" filter to the line.
temp = paeth;
for (posn = 0; posn < bpp; ++posn)
{
temp[posn] = (byte)(Buffer[posn] -
PngReader.Paeth(0, prevScanline[posn], 0));
}
for (posn = bpp; posn < bytesPerLine; ++posn)
{
temp[posn] = (byte)(Buffer[posn] -
PngReader.Paeth
(Buffer[posn - bpp],
prevScanline[posn],
prevScanline[posn - bpp]));
}
filter[0] = 4;
}
else
{
// No filter is needed for this scanline.
temp = Buffer;
filter[0] = 0;
}
// Write the filter type byte and the filtered scanline.
compressor.Write(filter, 0, 1);
compressor.Write(temp, 0, bytesPerLine);
// Swap the buffers and advance to the next scanline.
temp = Buffer;
Buffer = prevScanline;
prevScanline = temp;
++y;
}
