12. 对一幅灰度图像用最大类间方差法求阈值，并对其进行二值化。

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#include <cv.h>#include <highgui.h> #define GrayScale 256   int mytsu( IplImage *frame);int main(){    int a=0;     IplImage * test;    IplImage * test_1;    test = cvLoadImage("6013202130.bmp", 0);//图片路径是 ConsoleApplication4 文件夹里，同时实验要求转为灰度图片    test_1 = cvCreateImage(cvSize((test->width), (test->height)), IPL_DEPTH_8U, 1); //创建图像，给指针赋值    a= mytsu(test);    CvScalar s;    for (int i = 0; i < test->height; i++)    {        for (int j = 0; j < test->width; j++)        {            s = cvGet2D(test, i, j);            if (s.val[0] >a)                s.val[0] = 255;            else                s.val[0] = 0;            cvSet2D(test_1, i, j, s);        }    }    cvNamedWindow("原图—6013202130", CV_WINDOW_AUTOSIZE);    cvShowImage("原图—6013202130", test);    cvNamedWindow("对数变换—6013202130", CV_WINDOW_AUTOSIZE);    cvShowImage("对数变换—6013202130", test_1);    cvWaitKey(0);//等待按键    cvDestroyWindow("原图—6013202130");    cvDestroyWindow("对数变换—6013202130");    cvReleaseImage(&test);//释放内存。     cvReleaseImage(&test_1);    return 0;}int mytsu( IplImage *frame)   {    int width = frame->width;    int height = frame->height;    int pixelCount[GrayScale] = { 0 };    float pixelPro[GrayScale] = { 0 };    int i, j, pixelSum = width * height, threshold = 0;    uchar* data = (uchar*)frame->imageData;    //统计每个灰度级中像素的个数       for (i = 0; i < height; i++)    {        for (j = 0; j < width; j++)        {            pixelCount[(int)data[i * width + j]]++;        }    }    //计算每个灰度级的像素数目占整幅图像的比例       for (i = 0; i < GrayScale; i++)    {        pixelPro[i] = (float)pixelCount[i] / pixelSum;    }    //遍历灰度级[0,255],寻找合适的threshold       float w0, w1, u0tmp, u1tmp, u0, u1, deltaTmp, deltaMax = 0;    for (i = 0; i < GrayScale; i++)    {        w0 = w1 = u0tmp = u1tmp = u0 = u1 = deltaTmp = 0;        for (j = 0; j < GrayScale; j++)        {            if (j <= i)   //背景部分               {                w0 += pixelPro[j];                u0tmp += j * pixelPro[j];            }            else   //前景部分               {                w1 += pixelPro[j];                u1tmp += j * pixelPro[j];            }        }        u0 = u0tmp / w0;        u1 = u1tmp / w1;        deltaTmp = (float)(w0 *w1* pow((u0 - u1), 2));        if (deltaTmp > deltaMax)        {            deltaMax = deltaTmp;            threshold = i;        }    }    return threshold;}
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