protected override unsafe void ProcessFilter(UnmanagedImage sourceData, UnmanagedImage destinationData, Rectangle rect)
{
int pixelSize = Image.GetPixelFormatSize(sourceData.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 = sourceData.Stride;
int dstStride = destinationData.Stride;
int srcOffset = srcStride - rect.Width * pixelSize;
int dstOffset = dstStride - rect.Width * pixelSize;
// loop and array indexes
int i, j, t;
// processing square's radius
int radius = size >> 1;
// number of elements
int c;
// array to hold pixel values (R, G, B)
byte[] r = new byte[size * size];
byte[] g = new byte[size * size];
byte[] b = new byte[size * size];
byte* src = (byte*)sourceData.ImageData.ToPointer();
byte* dst = (byte*)destinationData.ImageData.ToPointer();
byte* p;
// allign pointers to the first pixel to process
src += (startY * srcStride + startX * pixelSize);
dst += (startY * dstStride + startX * pixelSize);
// do the processing job
if (destinationData.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++)
{
c = 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 (t < stopX)
{
g[c++] = src[i * srcStride + j];
}
}
}
// sort elements
Array.Sort(g, 0, c);
// get the median
*dst = g[c >> 1];
}
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)
{
c = 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 (t < stopX)
{
p = &src[i * srcStride + j * pixelSize];
r[c] = p[RGB.R];
g[c] = p[RGB.G];
b[c] = p[RGB.B];
c++;
}
}
}
// sort elements
Array.Sort(r, 0, c);
Array.Sort(g, 0, c);
Array.Sort(b, 0, c);
// get the median
t = c >> 1;
dst[RGB.R] = r[t];
dst[RGB.G] = g[t];
dst[RGB.B] = b[t];
}
src += srcOffset;
dst += dstOffset;
}
}
}
}