cvFindContours/findContours提取轮廓

opencv在提取轮廓时，C/C++有两种方式，有些许不同，结合查找的资料和补充，做个小笔记；

功能，提取满足一定面积阈值和宽高比例的轮廓；

主函数

static int getContoursByC(char* Imgname, double minarea = 100, double whRatio = 1);  static int getContoursByCplus(char* Imgname, double minarea=0, double whRatio=1);  int main()  {      char* filename = new char[50];      strcpy(filename, "../image/rl_4.jpg");      getContoursByCplus(filename);      delete[] filename;      return 0;  }  

API实现

cvFindContours形式

/*采用cvFindContours提取轮廓，并过滤掉小面积轮廓，最后将轮廓保存*/  /*采用cvFindContours提取轮廓，并过滤掉小面积轮廓，最后将轮廓保存*/static int getContoursByC(char* Imgname, double minarea, double whRatio){    IplImage* src = cvLoadImage(Imgname, CV_LOAD_IMAGE_GRAYSCALE);    if (!src)    {        printf("read data error!\n");        return -1;    }    IplImage* dst = cvCreateImage(cvGetSize(src), 8, 3);    //the parm. for cvFindContours    CvMemStorage* storage = cvCreateMemStorage(0);    CvSeq* contour = 0;    double maxarea = 0;    //for display    cvNamedWindow("Source", CV_WINDOW_NORMAL);    cvShowImage("Source", src);    //二值化    cvThreshold(src, src, 120, 255, CV_THRESH_BINARY);    //提取轮廓    cvFindContours(src, storage, &contour, sizeof(CvContour), CV_RETR_CCOMP, CV_CHAIN_APPROX_SIMPLE);    cvZero(dst);//清空数组    /*CvSeq* _contour为了保存轮廓的首指针位置，因为随后contour将用来迭代*/    CvSeq* _contour = contour;    int maxAreaIdx = -1, iteratorIdx = 0;//n为面积最大轮廓索引，m为迭代索引    for (int iteratorIdx = 0; contour != 0; contour = contour->h_next, iteratorIdx++/*更新迭代索引*/)    {        double tmparea = fabs(cvContourArea(contour));        if (tmparea > maxarea)        {            maxarea = tmparea;            maxAreaIdx = iteratorIdx;            continue;        }        if (tmparea < minarea)        {            //删除面积小于设定值的轮廓            cvSeqRemove(contour, 0);             continue;        }        CvRect aRect = cvBoundingRect(contour, 0);        if ((aRect.width / aRect.height)<whRatio)        {            //删除宽高比例小于设定值的轮廓            cvSeqRemove(contour, 0);             continue;        }        //CvScalar color = CV_RGB( rand()&255, rand()&255, rand()&255 );//创建一个色彩值        //CvScalar color = CV_RGB(0, 255, 255);        //max_level 绘制轮廓的最大等级。如果等级为0，绘制单独的轮廓。如果为1，绘制轮廓及在其后的相同的级别下轮廓。        //如果值为2，所有的轮廓。如果等级为2，绘制所有同级轮廓及所有低一级轮廓，诸此种种。        //如果值为负数，函数不绘制同级轮廓，但会升序绘制直到级别为abs(max_level)-1的子轮廓。         //cvDrawContours(dst, contour, color, color, -1, 1, 8);//绘制外部和内部的轮廓    }    contour = _contour; /*int k=0;*/    //统计剩余轮廓，并画出最大面积的轮廓    int count = 0;    for (; contour != 0; contour = contour->h_next)    {        count++;        double tmparea = fabs(cvContourArea(contour));        if (tmparea == maxarea /*k==n*/)        {            CvScalar color = CV_RGB(255, 0, 0);            cvDrawContours(dst, contour, color, color, -1, 1, 8);        }        /*k++;*/    }    printf("The total number of contours is:%d", count);    cvNamedWindow("Components", CV_WINDOW_NORMAL);    cvShowImage("Components", dst);    cvSaveImage("dst.jpg", dst);    //roateProcess(dst);    cvWaitKey(0);    //销毁窗口和图像存储    cvDestroyWindow("Source");    cvReleaseImage(&src);    cvDestroyWindow("Components");    cvReleaseImage(&dst);    return 0;}

findContours形式

static int getContoursByCplus(char* Imgname, double minarea, double whRatio){    cv::Mat src, dst, canny_output;    /// Load source image and convert it to gray    src = imread(Imgname, 0);    if (!src.data)    {        std::cout << "read data error!" << std::endl;        return -1;    }    blur(src, src, Size(3, 3));    //the pram. for findContours,    vector<vector<Point> > contours;    vector<Vec4i> hierarchy;    /// Detect edges using canny    Canny(src, canny_output, 80, 255, 3);    /// Find contours    findContours(canny_output, contours, hierarchy, CV_RETR_TREE, CV_CHAIN_APPROX_SIMPLE, Point(0, 0));    //CV_RETR_CCOMP, CV_CHAIN_APPROX_SIMPLE    double maxarea = 0;    int maxAreaIdx = 0;    for (int i = 0; i<contours.size(); i++)    {        double tmparea = fabs(contourArea(contours[i]));        if (tmparea>maxarea)        {            maxarea = tmparea;            maxAreaIdx = i;            continue;        }        if (tmparea < minarea)        {            //删除面积小于设定值的轮廓            contours.erase(contours.begin() + i);             std::wcout << "delete a small area" << std::endl;            continue;        }        //计算轮廓的直径宽高        Rect aRect =boundingRect(contours[i]);        if ((aRect.width / aRect.height)<whRatio)        {            //删除宽高比例小于设定值的轮廓            contours.erase(contours.begin() + i);             std::wcout << "delete a unnomalRatio area" << std::endl;            continue;        }    }    /// Draw contours,彩色轮廓    dst= Mat::zeros(canny_output.size(), CV_8UC3);    for (int i = 0; i< contours.size(); i++)    {        //随机颜色        Scalar color = Scalar(rng.uniform(0, 255), rng.uniform(0, 255), rng.uniform(0, 255));        drawContours(dst, contours, i, color, 2, 8, hierarchy, 0, Point());    }    // Create Window    char* source_window = "countors";    namedWindow(source_window, CV_WINDOW_NORMAL);    imshow(source_window, dst);    cv:: waitKey(0);    return 0;}