[函数名称]

  P分位法图像二值化

[算法说明]

  所谓P分位法图像分割，就是在知道图像中目标所占的比率Ratio时，循环不同的灰度值对图像进行

分割，并计算对应的目标所占的比率，如果该比率与Ratio的差值足够小，那么该阈值就是所求的最

佳分割阈值。

        /// <summary>
        /// P-Parameter method of image segmention.
        /// </summary>
        /// <param name="src">The source image.</param>
        /// <param name="P">The ratio of object, from 0 to 1.</param>
        /// <returns></returns>
         public static WriteableBitmap PParameterThSegment(WriteableBitmap src,double P) ////P参数法阈值分割
        {
            if (src != null)
            {
                int w = src.PixelWidth;
                int h = src.PixelHeight;
                WriteableBitmap dstImage = new WriteableBitmap(w, h);
                byte[] temp = src.PixelBuffer.ToArray();
                byte[] tempMask = (byte[])temp.Clone();
                //定义灰度图像信息存储变量
                int[] srcData = new int[w * h];
                //定义背景和目标像素个数变量
                int C1 = 0, C2 = 0;
                //定义阈值变量
                int Th = 0;
                for (int j = 0; j < h; j++)
                {
                    for (int i = 0; i < w; i++)
                    {
                        srcData[i + j * w] = (int)((double)tempMask[i * 4 + j * w * 4] * 0.114 + (double)tempMask[i * 4 + 1 + j * w * 4] * 0.587 + (double)tempMask[i * 4 + 2 + j * w * 4] * 0.299);
                    }
                }
                for (int T = 0; T <= 255; T++)
                {
                    for (int i = 0; i < srcData.Length; i++)
                    {
                        if (srcData[i] > T)
                        {
                            C1++;
                        }
                        else
                        {
                            C2++;
                        }
                    }
                    double t = Math.Abs((double)((double)C1 / ((double)C1 + (double)C2)) - P);
                    if (t < 0.01)
                    {
                        Th = T;
                        break;
                    }
                    C1 = 0;
                    C2 = 0;
                }
                for (int j = 0; j < h; j++)
                {
                    for (int i = 0; i < w; i++)
                    {
                        temp[i * 4 + j * w * 4] = temp[i * 4 + 1 + j * w * 4] = temp[i * 4 + 2 + j * w * 4] = (byte)(srcData[i + j * w] < Th ? 0 : 255);
                    }
                }
                Stream sTemp = dstImage.PixelBuffer.AsStream();
                sTemp.Seek(0, SeekOrigin.Begin);
                sTemp.Write(temp, 0, w * 4 * h);
                return dstImage;
            }
            else
            {
                return null;
            }
        }