public Bitmap Transform(Bitmap source)
{
//create a blank bitmap the same size as original
Bitmap newBitmap = new Bitmap(source.Width, source.Height);
//get a graphics object from the new image
Graphics g = Graphics.FromImage(newBitmap);
// create the negative color matrix
ColorMatrix colorMatrix = new ColorMatrix();
colorMatrix.Matrix00 = colorMatrix.Matrix11 = colorMatrix.Matrix22 = -1f;
colorMatrix.Matrix33 = colorMatrix.Matrix44 = 1f;
// create some image attributes
ImageAttributes attributes = new ImageAttributes();
attributes.SetColorMatrix(colorMatrix);
g.DrawImage(source, new Rectangle(0, 0, source.Width, source.Height),
0, 0, source.Width, source.Height, GraphicsUnit.Pixel, attributes);
//dispose the Graphics object
g.Dispose();
return newBitmap;
}