private void sobelEdgesFiltersItem_Click(object sender, System.EventArgs e)
{
// save original image
Bitmap originalImage = sourceImage;
// get grayscale image
sourceImage = Grayscale.CommonAlgorithms.RMY.Apply(sourceImage);
// apply edge filter
ApplyFilter(new SobelEdgeDetector());
// delete grayscale image and restore original
sourceImage.Dispose();
sourceImage = originalImage;
sobelEdgesFiltersItem.Checked = true;
}