[函数名称]

  洪水填充算法函数

WriteableBitmap FloodfillProcess(WriteableBitmap src,Point location, Color fillColor, int threshold)

2，以这个点为起点，将它压入栈中，假设我们要填充的颜色为A，则将该点颜色设置为A，然后判断它的四邻域像素，这里我们设置一个颜色阈值T，假设当前像素灰度值为P(x,y)，四邻域像素为M(n),n=1,2,3,4，那么判断当前像素与四邻域像素的灰度差值D=|P-M|，如果D小于T， 那么我们将该像素M作为下一个种子点，压入栈中，否则继续判断。如图中黑色像素的四邻域内有一灰色点，与其差值小于T，则把它作为新的种子点压入栈中，继续判断。

3，当栈为空时，种子填充结束，否则重做步骤2。

[函数代码]

       /// <summary>
        /// Flood fill.
        /// </summary>
        /// <param name="src">The source image.</param>
        /// <param name="location">The start point to be filled.</param>
        /// <param name="fillColor">The color to be filled.</param>
        /// <param name="threshold">One parameter to control fill effect, from 0 to 255.</param>
        /// <returns></returns>
         public static WriteableBitmap FloodfillProcess(WriteableBitmap src,Point location, Color fillColor, int threshold)////洪水填充算法
         {
             if (src != null)
             {
                 int w = src.PixelWidth;
                 int h = src.PixelHeight;
                 Stack<Point> fillPoints = new Stack<Point>(w * h);
                 int[,] mask = new int[w, h];
                 WriteableBitmap fillImage = new WriteableBitmap(w, h);
                 byte[] temp = src.PixelBuffer.ToArray();
                 byte[] tempMask = (byte[])temp.Clone();
                 Color backColor = Color.FromArgb(0,tempMask[(int)location.X * 4 + 2 + (int)location.Y * w * 4], tempMask[(int)location.X * 4 + 1 + (int)location.Y * w * 4], tempMask[(int)location.X * 4 + (int)location.Y * w * 4]);
                 int gray = (int)((backColor.R + backColor.G + backColor.B) / 3);
                 if (location.X < 0 || location.X >= w || location.Y < 0 || location.Y >= h) return null;
                 fillPoints.Push(new Point(location.X, location.Y));
                 while (fillPoints.Count > 0)
                 {
                     Point p = fillPoints.Pop();
                     mask[(int)p.X, (int)p.Y] = 1;
                     tempMask[4 * (int)p.X + (int)p.Y * w*4] = (byte)fillColor.B;
                     tempMask[4 * (int)p.X + 1 + (int)p.Y * w*4] = (byte)fillColor.G;
                     tempMask[4 * (int)p.X + 2 +(int) p.Y * w*4] = (byte)fillColor.R;
                     if (p.X > 0 && (Math.Abs(gray - (int)((tempMask[4 * ((int)p.X - 1) + (int)p.Y * w * 4] + tempMask[4 * ((int)p.X - 1) + 1 + (int)p.Y * w * 4] + tempMask[4 * ((int)p.X - 1) + 2 + (int)p.Y * w * 4]) / 3)) < threshold) && (mask[(int)p.X - 1, (int)p.Y] != 1))
                     {
                         tempMask[4 * ((int)p.X - 1) + (int)p.Y * w*4] = (byte)fillColor.B;
                         tempMask[4 * ((int)p.X - 1) + 1 + (int)p.Y * w*4] = (byte)fillColor.G;
                         tempMask[4 * ((int)p.X - 1) + 2 + (int)p.Y * w*4] = (byte)fillColor.R;
                         fillPoints.Push(new Point(p.X - 1, p.Y));
                         mask[(int)p.X - 1, (int)p.Y] = 1;
                     }
                     if (p.X < w - 1 && (Math.Abs(gray - (int)((tempMask[4 * ((int)p.X + 1) + (int)p.Y * w * 4] + tempMask[4 * ((int)p.X + 1) + 1 + (int)p.Y * w * 4] + tempMask[4 * ((int)p.X + 1) + 2 + (int)p.Y * w * 4]) / 3)) < threshold) && (mask[(int)p.X + 1, (int)p.Y] != 1))
                     {
                         tempMask[4 * ((int)p.X + 1) + (int)p.Y * w * 4] = (byte)fillColor.B;
                         tempMask[4 * ((int)p.X + 1) + 1 + (int)p.Y * w * 4] = (byte)fillColor.G;
                         tempMask[4 * ((int)p.X + 1) + 2 + (int)p.Y * w * 4] = (byte)fillColor.R;
                         fillPoints.Push(new Point(p.X + 1, p.Y));
                         mask[(int)p.X + 1, (int)p.Y] = 1;
                     }
                     if (p.Y > 0 && (Math.Abs(gray - (int)((tempMask[4 * (int)p.X + ((int)p.Y - 1) * w * 4] + tempMask[4 * (int)p.X + 1 + ((int)p.Y - 1) * w * 4] + tempMask[4 * (int)p.X + 2 + ((int)p.Y - 1) * w * 4]) / 3)) < threshold) && (mask[(int)p.X, (int)p.Y - 1] != 1))
                     {
                         tempMask[4 * (int)p.X + ((int)p.Y - 1) * w * 4] = (byte)fillColor.B;
                         tempMask[4 * (int)p.X + 1 + ((int)p.Y - 1) * w * 4] = (byte)fillColor.G;
                         tempMask[4 * (int)p.X + 2 + ((int)p.Y - 1) * w * 4] = (byte)fillColor.R;
                         fillPoints.Push(new Point(p.X, p.Y - 1));
                         mask[(int)p.X, (int)p.Y - 1] = 1;
                     }
                     if (p.Y < h - 1 && (Math.Abs(gray - (int)((tempMask[4 * (int)p.X + ((int)p.Y + 1) * w * 4] + tempMask[4 * (int)p.X + 1 + ((int)p.Y + 1) * w * 4] + tempMask[4 * (int)p.X + 2 + ((int)p.Y + 1) * w * 4]) / 3)) < threshold) && (mask[(int)p.X, (int)p.Y + 1] != 1))
                     {
                         tempMask[4 * (int)p.X + ((int)p.Y + 1) * w * 4] = (byte)fillColor.B;
                         tempMask[4 * (int)p.X + 1 + ((int)p.Y + 1) * w * 4] = (byte)fillColor.G;
                         tempMask[4 * (int)p.X + 2 + ((int)p.Y + 1) * w * 4] = (byte)fillColor.R;
                         fillPoints.Push(new Point(p.X, p.Y + 1));
                         mask[(int)p.X, (int)p.Y + 1] = 1;
                     }
                 }
                 fillPoints.Clear();
                 temp = (byte[])tempMask.Clone();
                 Stream sTemp = fillImage.PixelBuffer.AsStream();
                 sTemp.Seek(0, SeekOrigin.Begin);
                 sTemp.Write(temp, 0, w * 4 * h);
                 return fillImage;
             }
             else
             {
                 return null;
             }
         }