protected override unsafe void ProcessFilter( UnmanagedImage image, Rectangle rect )
{
int pixelSize = ( image.PixelFormat == PixelFormat.Format8bppIndexed ) ? 1 : 3;
int width = rect.Width;
int height = rect.Height;
// processing start and stop X,Y positions
int startY = rect.Top;
int stopY = startY + height;
int startX = rect.Left;
int stopX = startX + width;
int startXInBytes = startX * pixelSize;
int stopXInBytes = stopX * pixelSize;
int stride = image.Stride;
// perform Y mirroring
if ( mirrorY )
{
// first pointer - points to the first pixel in line
byte* ptr1 = (byte*) image.ImageData.ToPointer( );
ptr1 += ( startY * stride + startX * pixelSize );
// second pointer - points to the last pixel in line
byte* ptr2 = (byte*) image.ImageData.ToPointer( );
ptr2 += ( startY * stride + ( stopX - 1 ) * pixelSize );
// offsets
int offset1 = stride - ( width >> 1 ) * pixelSize;
int offset2 = stride + ( width >> 1 ) * pixelSize;
// temporary value for swapping
byte v;
if ( image.PixelFormat == PixelFormat.Format8bppIndexed )
{
// grayscale mirroring
// for each line
for ( int y = startY; y < stopY; y++ )
{
// for each pixel
for ( int x = startX, halfStopX = startX + ( width >> 1 ); x < halfStopX; x++, ptr1++, ptr2-- )
{
// swap values
v = *ptr1;
*ptr1 = *ptr2;
*ptr2 = v;
}
ptr1 += offset1;
ptr2 += offset2;
}
}
else
{
// color mirroring
// for each line
for ( int y = startY; y < stopY; y++ )
{
// for each pixel
for ( int x = startX, halfStopX = startX + ( width >> 1 ); x < halfStopX; x++, ptr1 += 3, ptr2 -= 3 )
{
// swap Red
v = ptr1[RGB.R];
ptr1[RGB.R] = ptr2[RGB.R];
ptr2[RGB.R] = v;
// swap Green
v = ptr1[RGB.G];
ptr1[RGB.G] = ptr2[RGB.G];
ptr2[RGB.G] = v;
// swap Blue
v = ptr1[RGB.B];
ptr1[RGB.B] = ptr2[RGB.B];
ptr2[RGB.B] = v;
}
ptr1 += offset1;
ptr2 += offset2;
}
}
}
// perform X mirroring
if ( mirrorX )
{
int offset = stride - rect.Width * pixelSize;
// first pointer - points to the first line
byte* ptr1 = (byte*) image.ImageData.ToPointer( );
ptr1 += ( startY * stride + startX * pixelSize );
// second pointer - points to the last line
byte* ptr2 = (byte*) image.ImageData.ToPointer( );
ptr2 += ( ( stopY - 1 ) * stride + startX * pixelSize );
// temporary value for swapping
byte v;
// for each line
for ( int y = startY, halfStopY = startY + ( height >> 1 ); y < halfStopY; y++ )
{
// for each pixel
for ( int x = startXInBytes; x < stopXInBytes; x++, ptr1++, ptr2++ )
{
// swap values
v = *ptr1;
*ptr1 = *ptr2;
*ptr2 = v;
}
ptr1 += offset;
ptr2 += offset - stride - stride;
}
}
}
}
