opencv features2d对象识别

opencv features2d对象识别

在生活中，经常会遇到这样的一种情况，上班要出门的时候，突然找不到一件东西了，比如钥匙、手机或者手表等。这个时候一般在房间翻一遍各个角落来寻找不见的物品，最后突然一拍大脑，想到在某一个地方，在整个过程中有时候是很着急的，并且越着急越找不到，真是令人沮丧。但是，如果一个简单的计算机算法可以在几毫秒内就找到你要找的物品，你的感受如何？是不是很惊奇！这就是对象检测算法（object detection）的力量。虽然上述举的生活例子只是一个很简单的例子，但对象检测的应用范围很广，跨越多个不同的行业，从全天候监控到智能城市的实时车辆检测等。简而言之，物体检测是强大的深度学习算法中的一个分支。

代码：

        const Ptr<AKAZE> &detetor = AKAZE::create();
        vector<KeyPoint> oneKeyPoint;
        vector<KeyPoint> twoKeyPoint;
        Mat oneDes, twoDes;
        //角点查找和特征向量计算描述
        detetor->detectAndCompute(oneMat, Mat(), oneKeyPoint, oneDes);
        detetor->detectAndCompute(twoMat, Mat(), twoKeyPoint, twoDes);
        vector<DMatch> matches;
        //匹配描述向量
        const Ptr<BFMatcher> &bfm = BFMatcher::create();
        bfm->match(oneDes, twoDes, matches);


        //查找最大值最小值
        double minVal=100, maxVal = 0;
        for (int i = 0; i < matches.size(); ++i) {
            if (matches[i].distance>maxVal)
                maxVal=matches[i].distance;
            if (matches[i].distance<minVal)
                minVal=matches[i].distance;
        }

        //阈值筛选
        vector<DMatch> goods;
        for (int i = 0; i < oneDes.rows; ++i) {
            if (matches[i].distance<8*minVal){
                goods.push_back(matches[i]);
            }
        }

        //绘制焦点匹配
        drawMatches(oneMat, oneKeyPoint, twoMat, twoKeyPoint, goods, dstMat);
        
        vector<Point2f> obj;
        vector<Point2f> scene;
        for (int i = 0; i < goods.size(); ++i) {
            obj.push_back(oneKeyPoint[goods[i].queryIdx].pt);
            scene.push_back(twoKeyPoint[goods[i].trainIdx].pt);
        }
        //透视变换
        const Mat &H = getPerspectiveTransform(obj, scene);
        vector<Point2f> obj_corners(4);
        vector<Point2f> scene_corners(4);
        obj_corners[0]= Point2f(0,0);
        obj_corners[1]= Point2f(oneMat.cols,0);
        obj_corners[2]= Point2f(oneMat.cols,oneMat.rows);
        obj_corners[3]= Point2f(0,oneMat.rows);
        perspectiveTransform(obj_corners, scene_corners, H);

        //画出匹配区域
        Point2f offset(oneMat.cols, 0);
        line(dstMat, scene_corners[0]+offset, scene_corners[1]+offset,Scalar(0,255,0),4);
        line(dstMat, scene_corners[1]+offset, scene_corners[2]+offset,Scalar(0,255,0),4);
        line(dstMat, scene_corners[2]+offset, scene_corners[3]+offset,Scalar(0,255,0),4);
        line(dstMat, scene_corners[3]+offset, scene_corners[0]+offset,Scalar(0,255,0),4);



        LOGI("jason min max %f %f", minVal , maxVal);