对源图像指定区域（通过矩形的左上角和右下角的坐标点指定）使用最小误差最佳阈值法，通过迭代获得该区域的最佳阈值.rar

//最小误差最佳阈值法 unsigned char LEThreshold(IplImage *pSrcImg,CvPoint rect_top_left,CvPoint rect_bottom_right)// { const unsigned char* lpSrc; unsigned char pixel; int i,j; //直方图数组 long lHistogram[256]; //阈值，最大灰度值与最小灰度值，两个区域的平均灰度值 unsigned char iThreshold,iNewThreshold,iMaxGrayValue,iMinGrayValue,iMeanLGrayValue,iMeanHGrayValue; //用于计算区域灰度平均值的中间变量 long lP1,lP2,lS1,lS2; //迭代次数 int iIterationTimes; // int lWidth ; // int lHeight ; for(i = 0; i < 256; i++) { lHistogram[i] = 0; } // lWidth = pSrcImg->width; // lHeight = pSrcImg->height; //获取直方图 iMaxGrayValue = 0;//初始化最大灰度值为0 iMinGrayValue = 255;//最小灰度值为255 for(i = rect_top_left.y; i < rect_bottom_right.y ;i++) { lpSrc = (unsigned char*)&pSrcImg->imageData [i*pSrcImg->widthStep]; for(j = rect_top_left.x; j< rect_bottom_right.x; j++) { pixel = lpSrc[j]; lHistogram[pixel]++;//填充灰度直方图 //寻找最大，最小灰度值 if(iMinGrayValue > pixel) { iMinGrayValue = pixel; } if(iMaxGrayValue < pixel) { iMaxGrayValue = pixel; } } } //迭代求最佳阈值 if (iMaxGrayValue-iMinGrayValue <5 ) { printf("iMaxGrayValue-iMinGrayValue 必须大于6"); return false; } //初始化阈值 iNewThreshold = (unsigned char)((float)(iMinGrayValue + iMaxGrayValue)/2.0+0.5); iThreshold = 0; //迭代过程中阈值不再变化退出循环，或迭代次数达到时退出 for(iIterationTimes = 0; iThreshold !=iNewThreshold && iIterationTimes < 100; iIterationTimes ++) { iThreshold = iNewThreshold; lP1 = 0; lP2 = 0; lS1 = 0; lS2 = 0; //求两个区域的灰度平均值 for(i = iMinGrayValue; i < iThreshold; i++) { lP1 += lHistogram[i] * i;//图像低灰度像素的总灰度值 lS1 += lHistogram[i];//低灰度像素的总像素量 } iMeanLGrayValue = (unsigned char)(lP1 / lS1);//低灰度区域的平均灰度值 for(i = iThreshold; i<=iMaxGrayValue; i++)//阈值上的点没计算 { lP2 += lHistogram[i] *i; lS2 += lHistogram[i]; } iMeanHGrayValue = (unsigned char)(lP2 / lS2);//高灰度像素的平均像素值 iNewThreshold = (unsigned char)((float)(iMeanLGrayValue + iMeanHGrayValue) / 2.0 + 0.5);//阈值为图像高、低像素域的中间值 if (iNewThreshold<=iMinGrayValue+2 || iNewThreshold>=iMaxGrayValue-2)//阈值太靠近图像的最低或最高灰度时退出 { //iThreshold = iNewThreshold; // CString cs; // cs.Format("iThreshold=%d",iThreshold); // AfxMessageBox(cs); break; } } return iThreshold; }