protected override unsafe void ProcessFilter( UnmanagedImage source, UnmanagedImage destination, Rectangle rect )
{
int pixelSize = Image.GetPixelFormatSize( source.PixelFormat ) / 8;
// processing start and stop X,Y positions
int startX = rect.Left;
int startY = rect.Top;
int stopX = startX + rect.Width;
int stopY = startY + rect.Height;
int srcStride = source.Stride;
int dstStride = destination.Stride;
int srcOffset = srcStride - rect.Width * pixelSize;
int dstOffset = dstStride - rect.Width * pixelSize;
// loop and array indexes
int i, j, t;
// kernel's radius
int radius = size >> 1;
// pixel value (min and max)
byte minR, maxR, minG, maxG, minB, maxB, v;
byte* src = (byte*) source.ImageData.ToPointer( );
byte* dst = (byte*) destination.ImageData.ToPointer( );
byte* p;
// allign pointers to the first pixel to process
src += ( startY * srcStride + startX * pixelSize );
dst += ( startY * dstStride + startX * pixelSize );
if ( destination.PixelFormat == PixelFormat.Format8bppIndexed )
{
// Grayscale image
// for each line
for ( int y = startY; y < stopY; y++ )
{
// for each pixel
for ( int x = startX; x < stopX; x++, src++, dst++ )
{
minG = 255;
maxG = 0;
// for each kernel row
for ( i = -radius; i <= radius; i++ )
{
t = y + i;
// skip row
if ( t < startY )
continue;
// break
if ( t >= stopY )
break;
// for each kernel column
for ( j = -radius; j <= radius; j++ )
{
t = x + j;
// skip column
if ( t < startX )
continue;
if ( ( i != j ) && ( t < stopX ) )
{
// find MIN and MAX values
v = src[i * srcStride + j];
if ( v < minG )
minG = v;
if ( v > maxG )
maxG = v;
}
}
}
// set destination pixel
v = *src;
*dst = ( v > maxG ) ? maxG : ( ( v < minG ) ? minG : v );
}
src += srcOffset;
dst += dstOffset;
}
}
else
{
// RGB image
// for each line
for ( int y = startY; y < stopY; y++ )
{
// for each pixel
for ( int x = startX; x < stopX; x++, src += pixelSize, dst += pixelSize )
{
minR = minG = minB = 255;
maxR = maxG = maxB = 0;
// for each kernel row
for ( i = -radius; i <= radius; i++ )
{
t = y + i;
// skip row
if ( t < startY )
continue;
// break
if ( t >= stopY )
break;
// for each kernel column
for ( j = -radius; j <= radius; j++ )
{
t = x + j;
// skip column
if ( t < startX )
continue;
if ( ( i != j ) && ( t < stopX ) )
{
p = &src[i * srcStride + j * pixelSize];
// find MIN and MAX values
// red
v = p[RGB.R];
if ( v < minR )
minR = v;
if ( v > maxR )
maxR = v;
// green
v = p[RGB.G];
if ( v < minG )
minG = v;
if ( v > maxG )
maxG = v;
// blue
v = p[RGB.B];
if ( v < minB )
minB = v;
if ( v > maxB )
maxB = v;
}
}
}
// set destination pixel
// red
v = src[RGB.R];
dst[RGB.R] = ( v > maxR ) ? maxR : ( ( v < minR ) ? minR : v );
// green
v = src[RGB.G];
dst[RGB.G] = ( v > maxG ) ? maxG : ( ( v < minG ) ? minG : v );
// blue
v = src[RGB.B];
dst[RGB.B] = ( v > maxB ) ? maxB : ( ( v < minB ) ? minB : v );
}
src += srcOffset;
dst += dstOffset;
}
}
}
}