public static Bitmap Binary(Bitmap img)
{
int width = img.Width;
int height = img.Height;
BitmapData bdata = img.LockBits(new Rectangle(0, 0, width, height), ImageLockMode.ReadWrite,
PixelFormat.Format32bppRgb);
unsafe
{
byte* start = (byte*)bdata.Scan0.ToPointer();
for (int i = 0; i < height; i++)
{
for (int j = 0; j < width; j++)
{
if (start[0] != 255)
{
start[0] = start[1] = start[2] = 0;
}
start += 4;
}
start += bdata.Stride - width * 4;
}
}
img.UnlockBits(bdata);
return img;
}