protected override unsafe void ProcessFilter( UnmanagedImage image, Rectangle rect )
{
int pixelSize = ( image.PixelFormat == PixelFormat.Format8bppIndexed ) ? 1 : 3;
// processing start and stop Y positions
int startY = rect.Top;
int stopY = startY + rect.Height;
// processing width and offset
int width = rect.Width;
int offset = image.Stride - width * pixelSize;
// loop indexes and temp vars
int i, j, k, x, t1, t2;
// line length to process
int len = (int) ( ( width - 1 ) / pixelWidth ) + 1;
// reminder
int rem = ( ( width - 1 ) % pixelWidth ) + 1;
// do the job
byte* src = (byte*) image.ImageData.ToPointer( );
// allign pointer to the first pixel to process
src += ( startY * image.Stride + rect.Left * pixelSize );
byte* dst = src;
if ( image.PixelFormat == PixelFormat.Format8bppIndexed )
{
// Grayscale image
int[] tmp = new int[len];
for ( int y1 = startY, y2 = startY; y1 < stopY; )
{
// collect pixels
Array.Clear( tmp, 0, len );
// calculate
for ( i = 0; ( i < pixelHeight ) && ( y1 < stopY ); i++, y1++ )
{
// for each pixel
for ( x = 0; x < width; x++, src++ )
{
tmp[(int) ( x / pixelWidth )] += (int) *src;
}
src += offset;
}
// get average values
t1 = i * pixelWidth;
t2 = i * rem;
for ( j = 0; j < len - 1; j++ )
tmp[j] /= t1;
tmp[j] /= t2;
// save average value to destination image
for ( i = 0; ( i < pixelHeight ) && ( y2 < stopY ); i++, y2++ )
{
// for each pixel
for ( x = 0; x < width; x++, dst++ )
{
*dst = (byte) tmp[(int) ( x / pixelWidth )];
}
dst += offset;
}
}
}
else
{
// RGB image
int[] tmp = new int[len * 3];
for ( int y1 = startY, y2 = startY; y1 < stopY; )
{
// collect pixels
Array.Clear( tmp, 0, len * 3 );
// calculate
for ( i = 0; ( i < pixelHeight ) && ( y1 < stopY ); i++, y1++ )
{
// for each pixel
for ( x = 0; x < width; x++, src += 3 )
{
k = ( x / pixelWidth ) * 3;
tmp[k] += src[RGB.R];
tmp[k + 1] += src[RGB.G];
tmp[k + 2] += src[RGB.B];
}
src += offset;
}
// get average values
t1 = i * pixelWidth;
t2 = i * rem;
for ( j = 0, k = 0; j < len - 1; j++, k += 3 )
{
tmp[k] /= t1;
tmp[k + 1] /= t1;
tmp[k + 2] /= t1;
}
tmp[k] /= t2;
tmp[k + 1] /= t2;
tmp[k + 2] /= t2;
// save average value to destination image
for ( i = 0; ( i < pixelHeight ) && ( y2 < stopY ); i++, y2++ )
{
// for each pixel
for ( x = 0; x < width; x++, dst += 3 )
{
k = ( x / pixelWidth ) * 3;
dst[RGB.R] = (byte) tmp[k];
dst[RGB.G] = (byte) tmp[k + 1];
dst[RGB.B] = (byte) tmp[k + 2];
}
dst += offset;
}
}
}
}
}
