opencv(7)----实例应用2

鼠标截图程序

主要功能

鼠标左键按下拖动显示轨迹，鼠标左键弹起显示截图并保存截图到本地

代码实现

mainwindow.cpp

Mat img=imread("D:\\1\\1.png");Mat temp;temp=img.clone();bool flag=false;//鼠标消息回调函数void OnMouse(int event, int x, int y, int flag, void* param){    switch(event)    {    case CV_EVENT_LBUTTONDOWN:  //鼠标左键按下        //cout<<"left button down"<<endl;        flag = true;        pt.x = x;        pt.y = y;        break;    case CV_EVENT_MOUSEMOVE:   //鼠标移动        //cout<<"mouse move"<<endl;        if(flag)        {            temp.copyTo(img);            rectangle(img, pt, Point(x, y), Scalar(0, 255, 0), 2, 8);        }        break;    case CV_EVENT_LBUTTONUP:   //鼠标左键弹起        //cout<<"left button up"<<endl;        flag = false;        ROI = temp(Rect(pt.x, pt.y, x-pt.x, y-pt.y));  //确定ROI区域        imshow("ROI", ROI);        imwrite("ROI.bmp", ROI);        break;    default:        break;    }}void main(){//鼠标截图功能namedWindow("Mouse", CV_WINDOW_AUTOSIZE);setMouseCallback("Mouse", OnMouse, 0);   //设置鼠标回调函数while(1)    {    imshow("Mouse", img);    if(27 == waitKey(10))  //Esc跳出循环    break;     }}

知识点详解

1.处理鼠标事件的通用代码

//鼠标消息回调函数void OnMouse(int event, int x, int y, int flag, void* param){    switch(event)    {    case CV_EVENT_LBUTTONDOWN:  //鼠标左键按下        cout<<"left button down"<<endl;        pt.x = x;        pt.y = y;        .....................        break;    case CV_EVENT_MOUSEMOVE:   //鼠标移动        cout<<"mouse move"<<endl;        .....................        break;    case CV_EVENT_LBUTTONUP:   //鼠标左键弹起        cout<<"left button up"<<endl;        ....................        break;    default:        break;    }}void main(){//鼠标截图功能namedWindow("Mouse", CV_WINDOW_AUTOSIZE);setMouseCallback("Mouse", OnMouse, 0);   //设置鼠标回调函数while(1){    imshow("Mouse", img);    if(27 == waitKey(10))  //Esc跳出循环    break;    }}

2. 使用按键事件时，必须将显示窗口放在while循环中

while(1){    imshow("Mouse", img);    if(27 == waitKey(10))  //Esc跳出循环    break;    }

但是，在滑动条事件中，无须使用while循环
3. 设置满足要求函数

Mat img=imread("D:\\1\\1.png");Mat temp;temp=img.clone();bool flag=false;//鼠标消息回调函数void OnMouse(int event, int x, int y, int flag, void* param){    switch(event)    {    case CV_EVENT_LBUTTONDOWN:  //鼠标左键按下        //cout<<"left button down"<<endl;        flag = true;        pt.x = x;        pt.y = y;        break;    case CV_EVENT_MOUSEMOVE:   //鼠标移动        //cout<<"mouse move"<<endl;        if(flag)        {            temp.copyTo(img);            rectangle(img, pt, Point(x, y), Scalar(0, 255, 0), 2, 8);        }        break;    case CV_EVENT_LBUTTONUP:   //鼠标左键弹起        //cout<<"left button up"<<endl;        flag = false;        ROI = temp(Rect(pt.x, pt.y, x-pt.x, y-pt.y));  //确定ROI区域        imshow("ROI", ROI);        imwrite("ROI.bmp", ROI);        break;    default:        break;    }}

4.

ROI = temp(Rect(pt.x, pt.y, x-pt.x, y-pt.y));  //确定ROI区域

之所以使用temp而不使用img
img是已经被绘制过矩形框的图像,temp是原图

temp(Rect(..,..))

可以用于获取一幅图像中的一部分

滑动条视频播放程序

主要功能

视频播放时，滑动条同时显示播放帧的位置和视频帧率，滑动条拖动时可以实现同步指定帧播放

代码实现

#include "mainwindow.h"#include <opencv2/opencv.hpp>#include <iostream>using namespace std;using namespace cv;int value;int framePos;/*将帧的位置设置为滑动条拖动的位置*/void onChange(int ,void *param){    VideoCapture cap=*(VideoCapture*)param;    cap.set(CV_CAP_PROP_POS_FRAMES,value);//设置视频帧位置}MainWindow::MainWindow(QWidget *parent):QMainWindow(parent){    VideoCapture cap;    Mat frame;    char strFPS[20];    cap.open("D:\\1.avi");    if(!cap.isOpened()){        cout<<"open false"<<endl;        return;    }    int totalFrame=cap.get(CAP_PROP_FRAME_COUNT);//获取总帧数    int FPS=cap.get(CAP_PROP_FPS);//获取速率    sprintf(strFPS,"Fps:%d",FPS);//格式化字符串    namedWindow("Video",CV_WINDOW_AUTOSIZE);    createTrackbar("FRAME","Video",&value,totalFrame,onChange,&cap);    cout<<FPS<<endl;    while(1){        //控制视频播放时trackbar的位置        framePos=cap.get(CV_CAP_PROP_POS_FRAMES);//获取当前视频帧位置        setTrackbarPos("FRAME","Video",framePos);//设置滑动条位置        getTrackbarPos()        cap.read(frame);        if(frame.empty()){            break;        }        putText(frame,strFPS,Point(5,30),CV_FONT_HERSHEY_COMPLEX_SMALL,1,Scalar(255,255,255),2,8);        imshow("Video",frame);        if(waitKey(1000/FPS)==27){            break;        }    }    cap.release();    destroyAllWindows();}MainWindow::~MainWindow(){}