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[7] { 1, 2, 3, 3, 3, 2, 1 }; int width = sourceBitmap.Width; int height = sourceBitmap.Height; BitmapData sourceData = sourceBitmap.LockBits(new Rectangle(0, 0, 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, 0, pixelBuffer.Length); sourceBitmap.UnlockBits(sourceData); float rgb = 0; for (int k = 0; k < pixelBuffer.Length; k += 4) { rgb = pixelBuffer[k] * 0.11f; rgb += pixelBuffer[k + 1] * 0.59f; rgb += pixelBuffer[k + 2] * 0.3f; pixelBuffer[k] = (byte)rgb; pixelBuffer[k + 1] = pixelBuffer[k]; pixelBuffer[k + 2] = pixelBuffer[k]; pixelBuffer[k + 3] = 255; } int[] susanMap = new int[height * width]; int offset = stride - width * 4; GCHandle srchandle = GCHandle.Alloc(susanMap, GCHandleType.Pinned); IntPtr susan = srchandle.AddrOfPinnedObject(); int dThreshold = 28; fixed (byte* pbuff = pixelBuffer, rbuff = resultBuffer) { byte* src = pbuff + stride * 3 + 3 * 4; int* br = (int*)susan + height * 3 + 3; byte* dst = rbuff + stride * 3 + 3 * 4; for (int offsetY = 3; offsetY < height - 3; offsetY++) { for (int offsetX = 3; offsetX < width - 3; offsetX++, src += 4,dst+=4, br++) { byte nucleusValue = *src; int usan = 0; int cx = 0, cy = 0; for (int i = -3; i <= 3; i++) { int r = rowRadius[i + 3]; 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 * 4]) / dThreshold), 6)); usan += c; cx += j * c; cy += i * c; } } if (usan < 28) usan = 28 -usan; else usan = 0; if ((usan < 6) && (cx != 0 || cy != 0)) { *dst = 255; dst[1] = 255; dst[2] = 255; dst[3] = 255; } else { *dst = 0; dst[1] = 0; dst[2] = 0; dst[3] = 255; } *br = usan; } src += 6 * 4 + offset; dst += 6 * 4 + offset; br += 6; } } Bitmap resultBitmap = new Bitmap(sourceBitmap.Width, sourceBitmap.Height); BitmapData resultData = resultBitmap.LockBits(new Rectangle(0, 0, resultBitmap.Width, resultBitmap.Height), ImageLockMode.WriteOnly, PixelFormat.Format32bppArgb); Marshal.Copy(resultBuffer, 0, 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(0, 0, 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, 0, pixelBuffer.Length); sourceBitmap.UnlockBits(sourceData); float rgb = 0; for (int k = 0; k < pixelBuffer.Length; k += 4) { rgb = pixelBuffer[k] * 0.11f; rgb += pixelBuffer[k + 1] * 0.59f; rgb += pixelBuffer[k + 2] * 0.3f; pixelBuffer[k] = (byte)rgb; pixelBuffer[k + 1] = pixelBuffer[k]; pixelBuffer[k + 2] = pixelBuffer[k]; pixelBuffer[k + 3] = 255; } int[] susanMap = new int[height * width]; int offset = stride - width * 4; 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(3, height - 3, (offsetY) => { for (int offsetX = 3; offsetX < width - 3; offsetX++) { OneSusan(offsetY, offsetX, (byte*)src, (byte*)dst, stride); } }); Bitmap resultBitmap = new Bitmap(sourceBitmap.Width, sourceBitmap.Height); BitmapData resultData = resultBitmap.LockBits(new Rectangle(0, 0, resultBitmap.Width, resultBitmap.Height), ImageLockMode.WriteOnly, PixelFormat.Format32bppArgb); Marshal.Copy(resultBuffer, 0, 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[7] { 1, 2, 3, 3, 3, 2, 1 }; int dThreshold = 28; src = (byte*)((int)src + stride * offsetY + offsetX * 4); dst = (byte*)((int)dst + stride * offsetY + offsetX * 4); byte nucleusValue = *src; int usan = 0; int cx = 0, cy = 0; float vX = 0, vY = 0, vXY = 0; for (int i = -3; i <= 3; i++) { int r = rowRadius[i + 3]; 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 * 4]) / dThreshold), 6)); usan += c; cx += j * c; cy += i * c; vX += j * j * c; vY += i * i * c; vXY += i * j * c; } } if (usan < 28) usan = 28 - usan; else usan = 0; if ((usan < 5) && (cx != 0 || cy != 0)) { *dst = 255; dst[1] = 255; dst[2] = 255; dst[3] = 255; } else { *dst = 0; dst[1] = 0; dst[2] = 0; dst[3] = 255; } }
示例下载（除Susan 方法之外的代码来自https://softwarebydefault.com/2013/05/11/image-edge-detection/)