基于c++计算矩形重叠面积代码实例

#include <iostream>
#include <opencv2/opencv.hpp>

using namespace std;
using namespace cv;

int main()
{
  // 1. 新建一个画布，把矩形画在画布上, 注意，矩形一定要在画布里面，不能在画布外面或者边上
  Mat canvaCaluateRectangleOverlap(100, 100, CV_8UC1, Scalar(0, 0, 0));

  // 2. 把两个矩形都画在画布上
  Rect rect1 = Rect(10, 10, 20, 20);
  Rect rect2 = Rect(20, 20, 20, 30);
  //为了使用fillPoly填充画布需要生成Point
  Point rect1Point[1][4];
  rect1Point[0][0] = Point(rect1.x, rect1.y);
  rect1Point[0][1] = Point(rect1.x + rect1.width, rect1.y);
  rect1Point[0][2] = Point(rect1.x + rect1.width, rect1.y + rect1.height);
  rect1Point[0][3] = Point(rect1.x, rect1.y + rect1.height);

  // 以下是用轮廓法计算矩形面积的方法，可以看看，但是实际使用当然还是 width*height
  //vector<Point> rect1Contours;
  //rect1Contours.push_back(Point(10, 10));
  //rect1Contours.push_back(Point(30, 10));
  //rect1Contours.push_back(Point(30, 30));
  //rect1Contours.push_back(Point(10, 30));
  //int rect1ContourArea = contourArea(rect1Contours);
  //cout << "rect1ContourArea : " << rect1ContourArea << endl;

  const Point* pointConst1[1] = { rect1Point[0] };
  int npt[] = { 4 };
  fillPoly(canvaCaluateRectangleOverlap, pointConst1, npt, 1, Scalar(255, 255, 255));

  Point rect2Point[1][4];
  rect2Point[0][0] = Point(rect2.x, rect2.y);
  rect2Point[0][1] = Point(rect2.x + rect2.width, rect2.y);
  rect2Point[0][2] = Point(rect2.x + rect2.width, rect2.y + rect2.height);
  rect2Point[0][3] = Point(rect2.x, rect2.y + rect2.height);
  const Point* pointConst2[1] = { rect2Point[0] };
  fillPoly(canvaCaluateRectangleOverlap, pointConst2, npt, 1, Scalar(255, 255, 255));

  // 3. 找出画布的轮廓
  vector<vector<Point> > canvaContours;
  vector<Vec4i> hierarchy;
  findContours(canvaCaluateRectangleOverlap, canvaContours, hierarchy, RETR_EXTERNAL, CHAIN_APPROX_SIMPLE, Point(0, 0));

  // 修正结果的偏移量，会差1个或0个像素，这里不考虑这个，大家有时间可以列举出每种情况计算出来
  int offset = 0;
  // 4. 对画布轮廓进行判断 （如果轮廓数等于1并且这两个矩形不是相邻就可以证明矩形是相交的）
  if (canvaContours.size() == 1 && rect1.x+rect1.width != rect2.x && rect2.x+rect2.width != rect1.x && rect1.y+rect1.height != rect2.y && rect2.y+rect2.height != rect1.y)
  {
    // 当矩形相交时，用计算轮廓面积的方法计算出相交多边形的面积（注意，这边会差0个或1个偏移量，所以本方式最适合计算重叠率，一个近似的数）
    int canvaContourArea = contourArea(canvaContours[0]) + offset;
    // 重叠的面积数 = 两个矩形面积的交集 - 两个矩形面积的并集 （要理解这个，好好去画图你就明白了）
    int rectangleOveralpArea = rect1.width * rect1.height + rect2.width * rect2.height - canvaContourArea;
    cout << "The two rectangles are overlapping. " << endl;
    cout << "retangleOverlapArea = " << rectangleOveralpArea << endl;
  }
  else {
    cout << "The two rectangles do not overlap. " << endl;
  }
  return 0;
}