Opencv 使用Rect选取与设置窗口ROI

首先看一下Rect对象的定义：

typedef Rect_<int> Rect;

再看Rect_的定义：

/*!  The 2D up-right rectangle class  The class represents a 2D rectangle with coordinates of the specified data type.  Normally, cv::Rect ~ cv::Rect_<int> is used.*/template<typename _Tp> class Rect_{public:    typedef _Tp value_type;    //! various constructors    Rect_();    Rect_(_Tp _x, _Tp _y, _Tp _width, _Tp _height);    Rect_(const Rect_& r);    Rect_(const CvRect& r);    Rect_(const Point_<_Tp>& org, const Size_<_Tp>& sz);    Rect_(const Point_<_Tp>& pt1, const Point_<_Tp>& pt2);    Rect_& operator = ( const Rect_& r );    //! the top-left corner    Point_<_Tp> tl() const;    //! the bottom-right corner    Point_<_Tp> br() const;    //! size (width, height) of the rectangle    Size_<_Tp> size() const;    //! area (width*height) of the rectangle    _Tp area() const;    //! conversion to another data type    template<typename _Tp2> operator Rect_<_Tp2>() const;    //! conversion to the old-style CvRect    operator CvRect() const;    //! checks whether the rectangle contains the point    bool contains(const Point_<_Tp>& pt) const;    _Tp x, y, width, height; //< the top-left corner, as well as width and height of the rectangle};

从上面的定义至少可以发现两点：

• 类Rect_的类模板中的数据类型Tp在Rect中被指定为整型
• 从Rect_的构造函数可以看出，其形参列表一共有6种形式
  
  1. Rect_()，形参列表为空，即定义一个空窗口（默认值为：x=y=width=height=0）
  2. Rect_(_Tp _x, _Tp _y, _Tp _width, _Tp _height)，定义一个左上角点坐标为(_x, _y)的_width*_height矩形窗口
  3. Rect_(const Rect_& r)，使用其他的Rect_对象初始化
  4. Rect_(const CvRect& r)，使用CvRect对象初始化
  5. Rect_(const Point_<Tp>& org, const Size<Tp>& sz)，分别将位置坐标(_x, _y)和窗口大小(_width, _height)用Point和Size_对象初始化
  6. Rect_(const Point_<Tp>& pt1, const Point<Tp>& pt2)，分别将坐标位置(_x, _y)和窗口大小(_width, _height)用Point和Point_对象初始化
  7. 在OpenCV库中，图像像素坐标与所在行列数的对应关系为：x -> col, y -> row, width -> cols, height -> rows

下面给出一段代码，基本可以把Rect的常见用法涵盖

Mat image = imread("C:\\Users\\Leo\\Desktop\\lena.jpg");Rect rect1(256, 256, 128, 128);Rect rect2(224, 224, 128, 128);Mat roi1;image(rect1).copyTo(roi1); // copy the region rect1 from the image to roi1imshow("1", roi1);waitKey(0);Mat roi2;image(rect2).copyTo(roi2); // copy the region rect2 from the image to roi2imshow("2", roi2);waitKey(0);cv::Rect rect3 = rect1&rect2; // intersection of the two setsMat roi3;image(rect3).copyTo(roi3);imshow("3", roi3);waitKey(0);Rect rect4 = rect1|rect2; // union of the two sets (the minimum bounding rectangle)Mat roi4;image(rect4).copyTo(roi4);imshow("4", roi4);waitKey(0);Rect rect5(10, 10, 128, 128);roi1.copyTo(image(rect5)); // copy the region rect1 to the designated region in the imageimshow("5", image);waitKey(0);

结果为

注：本文转自yhl_leo的CSDN博客