Use the mouse
Custom mouse function
void cv::setMouseCallback (
const String & winname,
MouseCallback onMouse,
void * userdata = 0 )
The function definition contains three parameters, namely the mouse function when placed in the window to which the mouse event occurred which the callback function is called, and what values passed to the callback function.
Defined callback function
The callback function must satisfy the following structure
void MouseCallback(
int event,
int x,
int y,
int flag,
void *userdata
)
Event first parameter, is a variable of type int, specifically for receiving the received mouse event type which, briefly a few examples where
| variable name | significance |
|---|---|
| EVENT_MOUSEMOVE | Mouse movement |
| EVENT_LBUTTONDOWN | Press the left mouse button |
| EVENT_RBUTTONDOWN | Press the right mouse button |
| EVENT_LBUTTONUP | Release the left mouse button |
| EVENT_RBUTTONUP | Right-release |
The second and third parameters to receive the coordinates of the mouse position, this position is a companion picture, not window coordinates of
the fourth parameter flag, meaning the event is quite similar parameters, indicates that the mouse down event has completed, shift and the like check key is pressed.
Specific examples
This example is a reference to "Opencv3 programming entry" Write down (p79 page)
The operating principle is the following program, when the mouse button is pressed when the start of the drawing, when the left mouse button to end the drawing release, mouse movement offset length and width of the picture. srcImage picture as the backsheet, the side length of the rectangle drawn above is offset to the mouse down released. And tempImage picture is an intermediate amount, drawn from the left mouse button is pressed to release the mouse button all rectangles in this process. However, according to the program book, draw pictures of srcImage negative side length of time to do a correction, but this step was not done on tempImage.
But I do not need to find the coordinates of the rectangle rect re-conversion, width and height are negative, it still can be a normal drawing.
#include<opencv2/opencv.hpp>
using namespace cv;
//程序说明：实现功能为鼠标按下后可以拖动进行绘制矩形框
bool g_value = false;//全局变量，用来判断什么时候开始画矩形框
Rect g_rect(-1,-1,0,0);//用来绘图的矩阵
void DrawRectangle(Mat& m, Rect r) //用来绘制矩形的函数
{
Scalar s(255, 0, 255);//相当于定义三通道的颜色，三通道分别是255,0,255
rectangle(m, g_rect, s);//用定义的颜色s，在图像m中绘制矩形g_rect
}
void MouseCallBack(int event,int x,int y,int flags,void* param)//回调函数
{
Mat m = *(Mat*)param;
switch (event)
{
case(EVENT_MOUSEMOVE):
if (g_value)//如果鼠标左键按下，g_value变为真，运行进行绘图，绘图矩阵记录鼠标移动的距离，作为宽和高
{
g_rect.width = x - g_rect.x;
g_rect.height = y - g_rect.y;
}
break;
case(EVENT_LBUTTONDOWN): //鼠标左键按下的时候，给矩阵重新定义初始位置
g_value = true;
g_rect = Rect(x, y, 0, 0);
break;
case(EVENT_LBUTTONUP): //鼠标左键放开的时候，把矩形画入srcImage。
g_value = false;
DrawRectangle(m, g_rect);
break;
}
}
int main()
{
Mat srcImage, tempImage; //两个用来存放图片的变量，在绘图中srcImage绘制最后的图片，tempImage绘制绘制中间过程的图片
srcImage = imread("1.jpg");
srcImage.copyTo(tempImage);
namedWindow("a", WINDOW_AUTOSIZE);
setMouseCallback("a", MouseCallBack, (void*)&srcImage); //鼠标函数
while(1)
{
srcImage.copyTo(tempImage);
if (g_value)
{
DrawRectangle(tempImage, g_rect); //这句话实际上是在记录整个鼠标的移动过程
}
imshow("a", tempImage);
if (waitKey(10) == 27)break;//按ESC键退出
}
return 0;
}
Operating results are as follows:
