C# Susan边缘检测(Susan Edge Detection)

Susan边缘检测，方法简单，效率高，具体参照 The SUSAN Edge Detector in Detail， 修改dThreshold值，可以改变检测效果，用参照提供的重心法、力矩法可得到边缘方向；

        /// https://users.fmrib.ox.ac.uk/~steve/susan/susan/node6.html
        public unsafe static Bitmap SusanGray(this Bitmap sourceBitmap)
        {
            int[] rowRadius = new int[] { , , , , , ,  };
            int width = sourceBitmap.Width;
            int height = sourceBitmap.Height;
            BitmapData sourceData = sourceBitmap.LockBits(new Rectangle(, , width, height), ImageLockMode.ReadOnly, PixelFormat.Format32bppArgb);

            int stride = sourceData.Stride;
            byte[] pixelBuffer = new byte[stride * sourceData.Height];
            byte[] resultBuffer = new byte[stride * sourceData.Height];

            Marshal.Copy(sourceData.Scan0, pixelBuffer, , pixelBuffer.Length);
            sourceBitmap.UnlockBits(sourceData);

            float rgb = ;

            for (int k = ; k < pixelBuffer.Length; k += )
            {
                rgb = pixelBuffer[k] * 0.11f;
                rgb += pixelBuffer[k + ] * 0.59f;
                rgb += pixelBuffer[k + ] * 0.3f;

                pixelBuffer[k] = (byte)rgb;
                pixelBuffer[k + ] = pixelBuffer[k];
                pixelBuffer[k + ] = pixelBuffer[k];
                pixelBuffer[k + ] = ;
            }

            int[] susanMap = new int[height * width];

            int offset = stride - width * ;

            GCHandle srchandle = GCHandle.Alloc(susanMap, GCHandleType.Pinned);
            IntPtr susan = srchandle.AddrOfPinnedObject();

            int dThreshold = ;
            fixed (byte* pbuff = pixelBuffer, rbuff = resultBuffer)
            {
                byte* src = pbuff + stride *  +  * ;
                int* br = (int*)susan + height *  + ;
                byte* dst = rbuff + stride *  +  * ;

                for (int offsetY = ; offsetY < height - ; offsetY++)
                {
                    for (int offsetX = ; offsetX < width - ; offsetX++, src += ,dst+=, br++)
                    {
                        byte nucleusValue = *src;
                        int usan = ;

                        int cx = , cy = ;

                        for (int i = -; i <= ; i++)
                        {

                            int r = rowRadius[i + ];

                            byte* ptr = (byte*)((int)src + stride * i);

                            for (int j = -r; j <= r; j++)
                            {
                                int c = (int)Math.Exp(-Math.Pow((System.Math.Abs(nucleusValue - ptr[j * ]) / dThreshold), ));
                                usan += c;
                                cx += j * c;
                                cy += i * c;
                            }
                        }
                        if (usan < )
                            usan =  -usan;
                        else
                            usan = ;
                        if ((usan < ) && (cx !=  || cy != ))
                        {
                            *dst = ;
                            dst[] = ;
                            dst[] = ;
                            dst[] = ;
                        }
                        else
                        {
                            *dst = ;
                            dst[] = ;
                            dst[] = ;
                            dst[] = ;
                        }
                        *br = usan;
                    }
                    src +=  *  + offset;
                    dst +=  *  + offset;
                    br += ;
                }
            }

            Bitmap resultBitmap = new Bitmap(sourceBitmap.Width, sourceBitmap.Height);

            BitmapData resultData = resultBitmap.LockBits(new Rectangle(, ,
                                     resultBitmap.Width, resultBitmap.Height),
                                                      ImageLockMode.WriteOnly,
                                                 PixelFormat.Format32bppArgb);

            Marshal.Copy(resultBuffer, , resultData.Scan0, resultBuffer.Length);
            resultBitmap.UnlockBits(resultData);

            return resultBitmap;

        }

并行的方法：

        public unsafe static Bitmap ParallelSusan(this Bitmap sourceBitmap)
        {
            int width = sourceBitmap.Width;
            int height = sourceBitmap.Height;
            BitmapData sourceData = sourceBitmap.LockBits(new Rectangle(, , width, height), ImageLockMode.ReadOnly, PixelFormat.Format32bppArgb);

            int stride = sourceData.Stride;
            byte[] pixelBuffer = new byte[stride * sourceData.Height];
            byte[] resultBuffer = new byte[stride * sourceData.Height];

            Marshal.Copy(sourceData.Scan0, pixelBuffer, , pixelBuffer.Length);
            sourceBitmap.UnlockBits(sourceData);

            float rgb = ;

            for (int k = ; k < pixelBuffer.Length; k += )
            {
                rgb = pixelBuffer[k] * 0.11f;
                rgb += pixelBuffer[k + ] * 0.59f;
                rgb += pixelBuffer[k + ] * 0.3f;

                pixelBuffer[k] = (byte)rgb;
                pixelBuffer[k + ] = pixelBuffer[k];
                pixelBuffer[k + ] = pixelBuffer[k];
                pixelBuffer[k + ] = ;
            }

            int[] susanMap = new int[height * width];

            int offset = stride - width * ;
            GCHandle srchandle = GCHandle.Alloc(pixelBuffer, GCHandleType.Pinned);
            IntPtr src = srchandle.AddrOfPinnedObject();

            GCHandle dsthandle = GCHandle.Alloc(resultBuffer, GCHandleType.Pinned);
            IntPtr dst = dsthandle.AddrOfPinnedObject();

            GCHandle suhandle = GCHandle.Alloc(susanMap, GCHandleType.Pinned);
            IntPtr susan = suhandle.AddrOfPinnedObject();

                System.Threading.Tasks.Parallel.For(, height - , (offsetY) =>
                {
                    for (int offsetX = ; offsetX < width - ; offsetX++)
                    {
                        OneSusan(offsetY, offsetX, (byte*)src, (byte*)dst, stride);
                    }
                });

            Bitmap resultBitmap = new Bitmap(sourceBitmap.Width, sourceBitmap.Height);

            BitmapData resultData = resultBitmap.LockBits(new Rectangle(, ,
                                     resultBitmap.Width, resultBitmap.Height),
                                                      ImageLockMode.WriteOnly,
                                                 PixelFormat.Format32bppArgb);

            Marshal.Copy(resultBuffer, , resultData.Scan0, resultBuffer.Length);
            resultBitmap.UnlockBits(resultData);

            return resultBitmap;

        }
        public unsafe static void OneSusan(int offsetY, int offsetX, byte* src, byte* dst, int stride)
        {
            int[] rowRadius = new int[] { , , , , , ,  };
            int dThreshold = ;

            src = (byte*)((int)src + stride * offsetY + offsetX * );
            dst = (byte*)((int)dst + stride * offsetY + offsetX * );
            byte nucleusValue = *src;
            int usan = ;

            int cx = , cy = ;
            float vX = , vY = , vXY = ;
            for (int i = -; i <= ; i++)
            {

                int r = rowRadius[i + ];

                byte* ptr = (byte*)((int)src + stride * i);

                for (int j = -r; j <= r; j++)
                {
                    int c = (int)Math.Exp(-Math.Pow((System.Math.Abs(nucleusValue - ptr[j * ]) / dThreshold), ));
                    usan += c;
                    cx += j * c;
                    cy += i * c;
                    vX += j * j * c;
                    vY += i * i * c;
                    vXY += i * j * c;
                }
            }
            if (usan < )
                usan =  - usan;
            else
                usan = ;
            if ((usan < ) && (cx !=  || cy != ))
            {
                *dst = ;
                dst[] = ;
                dst[] = ;
                dst[] = ;
            }
            else
            {
                *dst = ;
                dst[] = ;
                dst[] = ;
                dst[] = ;
            }
        }

示例下载（除Susan 方法之外的代码来自https://softwarebydefault.com/2013/05/11/image-edge-detection/)