protected override unsafe void ProcessFilter( UnmanagedImage image, Rectangle rect )
{
// get pixel size
int pixelSize = Image.GetPixelFormatSize( image.PixelFormat ) / 8;
int startX = rect.Left;
int startY = rect.Top;
int stopX = startX + rect.Width;
int stopY = startY + rect.Height;
int offset = image.Stride - rect.Width * pixelSize;
// calculate posterization offset
int posterizationOffset = ( fillingType == PosterizationFillingType.Min ) ?
0 : ( ( fillingType == PosterizationFillingType.Max ) ?
posterizationInterval - 1 : posterizationInterval / 2 );
// calculate mapping array
byte[] map = new byte[256];
for ( int i = 0; i < 256; i++ )
{
map[i] = (byte) Math.Min( 255, ( i / posterizationInterval ) * posterizationInterval + posterizationOffset );
}
// do the job
byte* ptr = (byte*) image.ImageData.ToPointer( );
// allign pointer to the first pixel to process
ptr += ( startY * image.Stride + startX * pixelSize );
// check image format
if ( image.PixelFormat == PixelFormat.Format8bppIndexed )
{
// for each line
for ( int y = startY; y < stopY; y++ )
{
// for each pixel in line
for ( int x = startX; x < stopX; x++, ptr++ )
{
*ptr = map[*ptr];
}
ptr += offset;
}
}
else
{
// for each line
for ( int y = startY; y < stopY; y++ )
{
// for each pixel in line
for ( int x = startX; x < stopX; x++, ptr += pixelSize )
{
ptr[RGB.R] = map[ptr[RGB.R]];
ptr[RGB.G] = map[ptr[RGB.G]];
ptr[RGB.B] = map[ptr[RGB.B]];
}
ptr += offset;
}
}
}
}
