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/)