C++ 从文件 opencv 读取视频
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reading video from file opencv
提问by Ikemesit Ansa
Hi So I have written this code to capture a video from file
嗨所以我写了这段代码来从文件中捕获视频
#include <stdio.h>
#include <cv.h>
#include "highgui.h"
#include <iostream>
//using namespace cv
int main(int argc, char** argv)
{
CvCapture* capture=0;
IplImage* frame=0;
capture = cvCaptureFromAVI(char const* filename); // read AVI video
if( !capture )
throw "Error when reading steam_avi";
cvNamedWindow( "w", 1);
for( ; ; )
{
frame = cvQueryFrame( capture );
if(!frame)
break;
cvShowImage("w", frame);
}
cvWaitKey(0); // key press to close window
cvDestroyWindow("w");
cvReleaseImage(&frame);
}
Everytime I run it, I get the following error:
每次我运行它时，都会出现以下错误：
CaptureVideo.cpp: In function ‘int main(int, char**)':
CaptureVideo.cpp:13:28: error: expected primary-expression before ‘char'
CaptureVideo.cpp：在函数“int main(int, char**)”中：
CaptureVideo.cpp:13:28: 错误：'char' 之前的预期主表达式
Any help will be much appreciated.
任何帮助都感激不尽。
回答by Barney
This is C++ question, so you should use the C++ interface.
这是 C++ 问题，因此您应该使用 C++ 接口。
The errors in your original code:
原始代码中的错误：
- You forgot to remove
char const*incvCaptureFromAVI. - You don't wait for the frame to be displayed.
ShowImageonly works if it is followed by WaitKey. - I'm not sure if capture=NULL would mean that your file was not opened. Use
isOpenedinstead.
- 你忘记
char const*在cvCaptureFromAVI. - 您无需等待框架显示出来。
ShowImage仅在后面跟有 WaitKey 时才有效。 - 我不确定 capture=NULL 是否意味着您的文件没有打开。使用
isOpened来代替。
I have corrected your code and put it into the C++ interface, so it is a proper C++ code now. My rewrite does line-by-line the same as your program did.
我已更正您的代码并将其放入 C++ 接口，因此现在它是正确的 C++ 代码。我的重写与您的程序一样逐行进行。
//#include <stdio.h>
#include <opencv2/core/core.hpp>
#include <opencv2/highgui/highgui.hpp>
//#include <iostream>
using namespace cv;
using std::string;
int main(int argc, char** argv)
{
string filename = "yourfile.avi";
VideoCapture capture(filename);
Mat frame;
if( !capture.isOpened() )
throw "Error when reading steam_avi";
namedWindow( "w", 1);
for( ; ; )
{
capture >> frame;
if(frame.empty())
break;
imshow("w", frame);
waitKey(20); // waits to display frame
}
waitKey(0); // key press to close window
// releases and window destroy are automatic in C++ interface
}
