CaptchaRecogition.ImageProcess.PBinary C# (CSharp) Method

        public static Bitmap PBinary(Bitmap src, int v)
        {
            int w = src.Width;
            int h = src.Height;
            Bitmap dstBitmap = new Bitmap(src.Width, src.Height, PixelFormat.Format24bppRgb);
            BitmapData srcData = src.LockBits(new Rectangle(0, 0, w, h), ImageLockMode.ReadOnly,
                PixelFormat.Format24bppRgb);
            BitmapData dstData = dstBitmap.LockBits(new Rectangle(0, 0, w, h), ImageLockMode.WriteOnly,
                PixelFormat.Format32bppRgb);
            unsafe
            {
                byte* pIn = (byte*)srcData.Scan0.ToPointer();
                byte* pOut = (byte*)dstData.Scan0.ToPointer();
                byte* p;
                int r, g, b;
                for (int y = 0; y < h; y++)
                {
                    for (int x = 0; x < w; x++)
                    {
                        p = pIn;
                        r = p[2];
                        g = p[1];
                        b = p[0];
                        pOut[0] = pOut[1] = pOut[2] = (byte)(((byte)(0.2125 * r + 0.7154 * g + 0.0721 * b) >= v) ? 255 : 0);
                        //pOut[0] = pOut[1] = pOut[2] = (byte)(r >= v? 255 : 0);
                        pIn += 4;
                        pOut += 4;
                    }
                    pIn += srcData.Stride - w * 4;
                    pOut += srcData.Stride - w * 4;
                }
                src.UnlockBits(srcData);
                dstBitmap.UnlockBits(dstData);
                return dstBitmap;
            }
        }