在OpenCV中，提供了视频读写类VideoCapture，该类可以方便的连接计算机的摄像头，并将摄像头的视频按照帧写入单幅图像，以便进行图像处理。下面的例子中，OpenCV打开摄像头，并将图像输出到Frame中。
int main( int argc, char** argv ) {
if (argc != 2) {
help(argv);
return 0;
}
cv::namedWindow( "Example 2-3",cv::WINDOW_AUTOSIZE );
cv::VideoCapture cap;
cap.open( string(argv[1]) );
cout <<"Opened file: "<<argv[1] <<endl;
cv::Mat frame;
for(;;) {
cap >> frame;
if( frame.empty() ) break; // Ran out of film
cv::imshow( "Example2-3", frame );
if( (char)cv::waitKey(33) >= 0 ) break;
}
return 0;
}
对读入的视频可以经过一定的处理再合成为视频写入硬盘进行保存，对视频的写入借助于OpenCV的视频写类VideoWriter，以下的示例展示了读取视频并输出帧，经过图像处理之再合成为视频。
int main( int argc, char** argv ) {
cv::namedWindow( "Example2-11", cv::WINDOW_AUTOSIZE );
cv::namedWindow( "Log_Polar",cv::WINDOW_AUTOSIZE );
// ( Note: could capture from a camera by giving a cameraid as an int.)
cv::VideoCapturecapture( argv[1] );
double fps = capture.get(CV_CAP_PROP_FPS );
cv::Size size(
(int)capture.get(CV_CAP_PROP_FRAME_WIDTH ),
(int)capture.get(CV_CAP_PROP_FRAME_HEIGHT )
);
cv::VideoWriterwriter;
writer.open(argv[2], CV_FOURCC('M','J','P','G'), fps, size );
cv::Matlogpolar_frame, bgr_frame;
for(;;) {
capture>> bgr_frame;
if( bgr_frame.empty() ) break; // end if done
cv::imshow( "Example 2-11",bgr_frame );
cv::logPolar(
bgr_frame, // Input color frame
logpolar_frame, // Output log-polar frame
cv::Point2f( // Centerpoint for log-polar transformation
bgr_frame.cols/2, // x
bgr_frame.rows/2 // y
),
40, // Magnitude (scale parameter)
CV_WARP_FILL_OUTLIERS // Fill outliers with 'zero'
);
cv::imshow( "Log_Polar",logpolar_frame );
writer <<logpolar_frame;
char c = cv::waitKey(10);
if( c == 27 ) break; // allow the user to break out
}
writer.release();
capture.release();
}