OpenCV學習(32) 求輪廓的包圍盒

      在OpenCV中，能夠很方便的求輪廓包圍盒。包括矩形，圓形，橢圓形以及傾斜的矩形(包圍面積最小)集中包圍盒。用到的四個函數是：

Rect boundingRect(InputArray points)

void minEnclosingCircle(InputArray points, Point2f& center, float& radius)

RotatedRect minAreaRect(InputArray points)

RotatedRect fitEllipse(InputArray points)

 

輸入的參數都是輪廓，下面是程序代碼：

1. Rect和原型包圍盒代碼：

nt main( int argc, char** argv )
    {
    //裝入圖像
    src = imread("../ballon.jpg", 1 );

    //轉化為灰度圖並進行blur操作
    cvtColor( src, src_gray, CV_BGR2GRAY );
    blur( src_gray, src_gray, Size(3,3) );

    namedWindow( "source", CV_WINDOW_AUTOSIZE );
    imshow( "source", src );

    Mat threshold_output;
    vector<vector<Point> > contours;
    vector<Vec4i> hierarchy;

    //得到二值圖像
    threshold( src_gray, threshold_output, thresh, 255, THRESH_BINARY );
    //查找輪廓
    findContours( threshold_output, contours, hierarchy, CV_RETR_TREE, CV_CHAIN_APPROX_SIMPLE, Point(0, 0) );

    //對輪廓進行多邊形近似處理求得圓形和四邊形包圍盒
    vector<vector<Point> > contours_poly( contours.size() );
    vector<Rect> boundRect( contours.size() );
    vector<Point2f>center( contours.size() );
    vector<float>radius( contours.size() );

    //得到每個輪廓的包圍盒RECT以及園，園用中心和半徑表示
    for( int i = 0; i < contours.size(); i++ )
        { 
        approxPolyDP( Mat(contours[i]), contours_poly[i], 3, true );
        boundRect[i] = boundingRect( Mat(contours_poly[i]) );
        minEnclosingCircle( (Mat)contours_poly[i], center[i], radius[i] );
        }


    //畫輪廓以及它的四邊形和原型包圍盒
    Mat drawing = Mat::zeros( threshold_output.size(), CV_8UC3 );
    for( int i = 0; i< contours.size(); i++ )
        {
        Scalar color = Scalar( rng.uniform(0, 255), rng.uniform(0,255), rng.uniform(0,255) );
        drawContours( drawing, contours_poly, i, color, 1, 8, vector<Vec4i>(), 0, Point() );
        //tl是左上角坐標, br是右下角坐標
        rectangle( drawing, boundRect[i].tl(), boundRect[i].br(), color, 2, 8, 0 );
        circle( drawing, center[i], (int)radius[i], color, 2, 8, 0 );
        }

    namedWindow( "Contours", CV_WINDOW_AUTOSIZE );
    imshow( "Contours", drawing );


    while(1)
        waitKey(0);
    return(0);
    }

程序運行效果：

 

2. 橢圓形和傾斜的矩形包圍盒代碼：

int main( int argc, char** argv )
    {
    //裝入圖像
    src = imread("../ballon.jpg", 1 );

    //轉化為灰度圖並進行blur操作
    cvtColor( src, src_gray, CV_BGR2GRAY );
    blur( src_gray, src_gray, Size(3,3) );

    namedWindow( "source", CV_WINDOW_AUTOSIZE );
    imshow( "source", src );

    Mat threshold_output;
    vector<vector<Point> > contours;
    vector<Vec4i> hierarchy;

    //得到二值圖像
    threshold( src_gray, threshold_output, thresh, 255, THRESH_BINARY );
    //查找輪廓
    findContours( threshold_output, contours, hierarchy, CV_RETR_TREE, CV_CHAIN_APPROX_SIMPLE, Point(0, 0) );

    //查找輪廓的最小旋轉rect和橢圓包圍盒
    vector<RotatedRect> minRect( contours.size() );
    vector<RotatedRect> minEllipse( contours.size() );

    for( int i = 0; i < contours.size(); i++ )
        { minRect[i] = minAreaRect( Mat(contours[i]) );
    if( contours[i].size() > 5 )
        { minEllipse[i] = fitEllipse( Mat(contours[i]) ); }
        }

    //畫輪廓和包圍盒
    Mat drawing = Mat::zeros( threshold_output.size(), CV_8UC3 );
    for( int i = 0; i< contours.size(); i++ )
        {
        Scalar color = Scalar( rng.uniform(0, 255), rng.uniform(0,255), rng.uniform(0,255) );
        // 輪廓
        drawContours( drawing, contours, i, color, 1, 8, vector<Vec4i>(), 0, Point() );
        // 橢圓
        ellipse( drawing, minEllipse[i], color, 2, 8 );
        // 旋轉rect
        Point2f rect_points[4]; minRect[i].points( rect_points );
        for( int j = 0; j < 4; j++ )
            line( drawing, rect_points[j], rect_points[(j+1)%4], color, 1, 8 );
        }

    namedWindow( "Contours", CV_WINDOW_AUTOSIZE );
    imshow( "Contours", drawing );


    while(1)
        waitKey(0);
    return(0);
    }

程序運行效果：