OpenCV + CPP 系列（十一）鼠标事件

数据类型转换：void* 转成 Mat
Mat image = *((Mat*)userdata);

回调函数​​on_draw​​：以下鼠标事件说明：

• 按下鼠标左键：​​event == EVENT_LBUTTONDOWN​​ 此时记下坐标即可
• 移动鼠标时：​​event == EVENT_MOUSEMOVE​​ 确保有(x，y)方向的移动，并绘制框（绘制之前清空以前绘制的框），实时显示
• 抬起鼠标左键：​​event == EVENT_LBUTTONUP​​ 显示绘制框，显示ROI区域

示例：

头文件 ​​quick_opencv.h​​：声明类与公共函数

#pragma once
#include <opencv2\opencv.hpp>
using namespace cv;

class QuickDemo {
public:
  ...
  void mouse_drawing_Demo(Mat& image);
};

主函数调用该类的公共成员函数

#include <opencv2\opencv.hpp>
#include <quick_opencv.h>
#include <iostream>
using namespace cv;


int main(int argc, char** argv) {
  Mat src = imread("D:\\Desktop\\pugongying2.jpg");
  if (src.empty()) {
    printf("Could not load images...\n");
    return -1;
  }
  namedWindow("input", WINDOW_NORMAL);
  imshow("input", src);

  QuickDemo qk;

  ...
  //qk.polyline_drawing_Demo();
  qk.mouse_drawing_Demo(src);
  waitKey(0);
  destroyAllWindows();
  return 0;
}

源文件 ​​quick_demo.cpp​​：实现类与公共函数

Point sp(-1, -1);
Point ep(-1, -1);
Mat temp;
static void on_draw(int event, int x, int y, int flags, void* userdata) {
  Mat image = *((Mat*)userdata);
  if (event == EVENT_LBUTTONDOWN) {
    sp.x = x;
    sp.y = y;
    std::cout << "start point" << sp << std::endl;
  }
  else if (event == EVENT_LBUTTONUP) {
    ep.x = x;
    ep.y = y;
    int dx = ep.x - sp.x;
    int dy = ep.y - sp.y;
    if (dx > 0 && dy > 0) {
      Rect box(sp.x, sp.y, dx, dy);
      temp.copyTo(image);
      imshow("ROI区域", image(box));
      rectangle(image, box, Scalar(0, 0, 255), 2, 8, 0);
      imshow("鼠标绘制", image);

      // ready for next drawing
      sp.x = -1;
      sp.y = -1;
    }
  }
  else if (event == EVENT_MOUSEMOVE) {
    if (sp.x > 0 && sp.y > 0) {
      ep.x = x;
      ep.y = y;
      int dx = ep.x - sp.x;
      int dy = ep.y - sp.y;
      if (dx > 0 && dy > 0) {
        Rect box(sp.x, sp.y, dx, dy);
        temp.copyTo(image);
        rectangle(image, box, Scalar(0, 0, 255), 2, 8, 0);
        imshow("鼠标绘制", image);
      }
    }
  }
}


void QuickDemo::mouse_drawing_Demo(Mat& image) {
  namedWindow("鼠标绘制", WINDOW_AUTOSIZE);
  setMouseCallback("鼠标绘制", on_draw, (void*)&image);
  imshow("鼠标绘制", image);
  temp = image.clone();
}