ImageProcessor.Processor.ThresholdMM C# (CSharp) Method

        public Image ThresholdMM(float thresh)
        {
            Bitmap b = new Bitmap(_image);

            BitmapData bData = b.LockBits(new Rectangle(0, 0, _image.Width, _image.Height),ImageLockMode.ReadWrite, b.PixelFormat);

            byte bitsPerPixel = GetBitsPerPixel(bData.PixelFormat);

            int size=bData.Stride * bData.Height;
            byte[] data = new byte[size];

            System.Runtime.InteropServices.Marshal.Copy(bData.Scan0, data, 0, size);

            for (int i = 0; i < size; i+=bitsPerPixel/8)
            {
                double magnitude = Math.Sqrt(Math.Pow(data[i], 2) + Math.Pow(data[i + 1], 2) + Math.Pow(data[i + 2], 2));
                if (magnitude < thresh)
                {
                    data[i] = 0;
                    data[i + 1] = 0;
                    data[i + 2] = 0;
                }
                else
                {
                    data[i] = 255;
                    data[i + 1] = 255;
                    data[i + 2] = 255;
                }
            }

            System.Runtime.InteropServices.Marshal.Copy(data, 0, bData.Scan0, data.Length);

            b.UnlockBits(bData);

            return b;
        }