c++ - opencv/c++ 我如何只检测之前检测到的方形区域内的关键点

Question

我正在做我的项目，我遇到了一个问题，我不知道如何只从一个以前检测过的方形区域检测关键点。下面是我的演示，到目前为止，我的代码会检测正方形内外的关键点:https://www.youtube.com/watch?feature=player_embedded&v=3U8V6PhMnZ8

这是我找到正方形的代码:

       const int threshold_level = 2;
    for (int l = 0; l < threshold_level; l++)
    {

        gray = gray0 >= (l+1) * 255 / threshold_level;

        // Find contours and store them in a list
        findContours(gray, contours, CV_RETR_LIST, CV_CHAIN_APPROX_SIMPLE);

        // Test contours
        vector<Point> approx;
        for (size_t i = 0; i < contours.size(); i++)
        {
                // approximate contour with accuracy proportional
                // to the contour perimeter
                approxPolyDP(Mat(contours[i]), approx, arcLength(Mat(contours[i]), true)*0.02, true);

                // Note: absolute value of an area is used because
                // area may be positive or negative - in accordance with the
                // contour orientation
                if (approx.size() == 4 &&
                        fabs(contourArea(Mat(approx))) > 3000 &&
                        isContourConvex(Mat(approx)))
                {
                        double maxCosine = 0;

                        for (int j = 2; j < 5; j++)
                        {
                                double cosine = fabs(angle(approx[j%4], approx[j-2], approx[j-1]));
                                maxCosine = MAX(maxCosine, cosine);
                        }

                        if (maxCosine < 0.3)
                                squares.push_back(approx);
                }
        }
    }

这是我绘制正方形和角点的代码:

 const Point* p = &squares[i][0];
        int n = (int)squares[i].size();       
        Point p1 = squares[i][0];
        Point p2 = squares[i][1];
        Point p3 = squares[i][2];
        Point p4 = squares[i][3];
        cout<<"p1 is "<<p1<<" p2 is "<<p2<<" p3 is "<<p3<<" p4 is "<<p4<<endl;
        circle(image, squares[i][0], 3, Scalar(0,0,255), 5, 8, 0);
        circle(image, squares[i][1], 3, Scalar(0,255,255), 5, 8, 0);
        circle(image, squares[i][2], 3, Scalar(255,0,255), 5, 8, 0);
        circle(image, squares[i][3], 3, Scalar(255,255,0), 5, 8, 0);

        polylines(image, &p, &n, 1, true, Scalar(0,255,0), 3, CV_AA);

这是我检测关键点的代码:

    Mat gray_image;
    vector<KeyPoint> keyPoints; 
    cvtColor(image, gray_image, CV_BGR2GRAY); 
    FastFeatureDetector fast(60); 
    fast.detect(gray_image,keyPoints);  
    drawKeypoints(image, keyPoints,image, Scalar::all(255), DrawMatchesFlags::DRAW_OVER_OUTIMG); 

Answer 1

您可以使用裁剪图像

Rect r(left,top,width,height);//我们感兴趣的部分图片

Mat roi(fullImage, r);//将创建对原始图像的矩形 r 的引用。请注意，它不是拷贝。