[函数名称]

  二值图像轮廓提取         ContourExtraction(WriteableBitmap src) 

[算法说明]

  二值图像的轮廓提取对于图像识别，图像分割有着重要意义。该算法的核心就是将图像目标的内部点消除。所谓内部点，我们要根据当前像素点的邻域来进行判断，假设邻域窗口为3*3窗口，如果当前像素P(x,y)的八个邻域像素满足如下条件，则该点即内部点：

  1，P(x,y)为目标像素，假设目标像素为黑色0，背景像素为白色255，那么P(x,y)=0;

  2，P(x,y)的八个邻域像素均为目标像素0；

  我们把满足条件的内部点删除，换为背景点255，即可得到图像轮廓。

  内部点如下图所示：

[函数代码]

        /// <summary>
        /// Contour Extraction process.
        /// </summary>
        /// <param name="src">The source image.</param>
        /// <returns></returns>
        public static WriteableBitmap ContourExtraction(WriteableBitmap src)
        {
            if (src != null)
            {
                int w = src.PixelWidth;
                int h = src.PixelHeight;
                WriteableBitmap srcImage = new WriteableBitmap(w, h);
                byte[] temp = src.PixelBuffer.ToArray();
                byte[] tempMask = (byte[])temp.Clone();
                for (int j = 1; j < h-1; j++)
                {
                    for (int i = 4; i < w*4-4; i+=4)
                    {
                        if ((tempMask[i + j * w * 4] == 0) && (tempMask[i - 4 + j * w * 4] == 0) && (tempMask[i + 4 + j * w * 4] == 0) && (tempMask[i - 4 + (j - 1) * w * 4] == 0)
                            && (tempMask[i - 4 + (j + 1) * w * 4] == 0) && (tempMask[i + (j - 1) * w * 4] == 0) && (tempMask[i + (j + 1) * w * 4] == 0)
                            && (tempMask[i + 4 + (j - 1) * w * 4] == 0) && (tempMask[i + 4 + (j + 1) * w * 4] == 0))
                        {
                            temp[i + j * w * 4] = (byte)255;
                            temp[i + 1 + j * w * 4] = (byte)255;
                            temp[i + 2 + j * w * 4] = (byte)255;
                        }
                    }
                }
                Stream sTemp = srcImage.PixelBuffer.AsStream();
                sTemp.Seek(0, SeekOrigin.Begin);
                sTemp.Write(temp, 0, w * 4 * h);
                return srcImage;
            }
            else
            {
                return null;
            }
        }