每天一个opencv函数：鼠标操作setMouseCallback

opencv支持鼠标事件操作，通过setMouseCallback函数来设置鼠标事件的回调函数，从而使得每次操作鼠标之后就会调用对应的回调函数。

函数原型

void setMousecallback(const string& winname, MouseCallback onMouse, void* userdata=0);
//winname:窗口的名字
//onMouse:鼠标响应函数，回调函数。指定窗口里每次鼠标时间发生的时候，被调用的函数指针。
		//这个函数的原型应该为void on_Mouse(int event, int x, int y, int flags, void* param);
//userdate：传给回调函数的参数

在介绍一下回调函数

void on_Mouse(int event, int x, int y, int flags, void* param);
//event是 CV_EVENT_*变量之一
//x和y是鼠标指针在图像坐标系的坐标（不是窗口坐标系） 
//flags是CV_EVENT_FLAG的组合， param是用户定义的传递到setMouseCallback函数调用的参数。

示例

//鼠标事件测试
#define WINDOWS_NAME  "鼠标测试"

void on_MouseHandle(int event, int x, int y, int flage, void* param);
void DrawRectangle(Mat& img, Rect box);

Rect g_rectangle;
bool g_bDrawingBox = false;
RNG g_rng(12345);


int main()
{
  g_rectangle = Rect(-1, -1, 0, 0);
  Mat srcImage(600, 800, CV_8UC3), tempImage;
  srcImage.copyTo(tempImage);
  g_rectangle = Rect(-1, -1, 0, 0);
  srcImage = Scalar::all(0);

  namedWindow(WINDOWS_NAME);
  setMouseCallback(WINDOWS_NAME, on_MouseHandle, (void*)&srcImage);
  while (1)
  {
    srcImage.copyTo(tempImage);
    if (g_bDrawingBox)
      DrawRectangle(tempImage, g_rectangle);
    imshow(WINDOWS_NAME, tempImage);
    if (waitKey(10) == 27)
      break;
  }
  return 0;
}

void on_MouseHandle(int event, int x, int y, int flage, void* param)
{
  Mat& image = *(Mat*)param;
  switch (event)
  {
  case EVENT_MOUSEMOVE:
    if (g_bDrawingBox)
    {
      g_rectangle.width = x - g_rectangle.x;
      g_rectangle.height = y - g_rectangle.y;
    }
    break;
  case EVENT_LBUTTONDOWN:
    g_bDrawingBox = true;
    g_rectangle = Rect(x, y, 0, 0);
    break;
  case EVENT_RBUTTONDOWN:
    g_bDrawingBox = false;
    if (g_rectangle.width < 0)
    {
      g_rectangle.x += g_rectangle.width;
      g_rectangle.width *= -1;
    }
    if (g_rectangle.height < 0)
    {
      g_rectangle.y += g_rectangle.height;
      g_rectangle.height *= -1;
    }
    DrawRectangle(image, g_rectangle);
    break;
  }
}
void DrawRectangle(Mat& img, Rect box)
{
  rectangle(img, box.tl(), box.br(), Scalar(g_rng.uniform(0, 255), g_rng.uniform(0, 255), g_rng.uniform(0, 255)));
}

效果