从视频流获取图像

      利用ViSP也可以从输入视频流获取图像。支持格式包括avi，mp4，mov，ogv，flv等常见视频格式。下面创建的这个程序要求安装第三方库OpenCV。

#include <visp/vpDisplayGDI.h>
#include <visp/vpDisplayOpenCV.h>
#include <visp/vpDisplayX.h>
#include <visp/vpTime.h>//允许使用其下的计时函数
#include <visp/vpVideoReader.h>//允许读取视频流
int main(int argc, char** argv)
{
#if defined(VISP_HAVE_OPENCV) && (VISP_HAVE_OPENCV_VERSION >= 0x020100) || defined(VISP_HAVE_FFMPEG)
  try {
    std::string videoname = "video.mpg";
    for (int i=0; i<argc; i++) {
      if (std::string(argv[i]) == "--name")
        videoname = std::string(argv[i+1]);
      else if (std::string(argv[i]) == "--help") {
        std::cout << "
Usage: " << argv[0] << " [--name <video name>] [--help]
" << std::endl;
        return 0;
      }
    }
    vpImage<unsigned char> I;
    vpVideoReader g;//创建一个视频读取对象
    g.setFileName(videoname);//设置视频的文件名
    g.open(I);//初始化帧读取工具
    std::cout << "video name: " << videoname << std::endl;
    std::cout << "video framerate: " << g.getFramerate() << "Hz" << std::endl;
    std::cout << "video dimension: " << I.getWidth() << " " << I.getHeight() << std::endl;
#ifdef VISP_HAVE_X11
    vpDisplayX d(I);
#elif defined(VISP_HAVE_GDI)
    vpDisplayGDI d(I);
#elif defined(VISP_HAVE_OPENCV)
    vpDisplayOpenCV d(I);
#else
    std::cout << "No image viewer is available..." << std::endl;
#endif
    vpDisplay::setTitle(I, "Video reader");
    while (! g.end() ) {
      double t = vpTime::measureTimeMs();
      g.acquire(I);
      vpDisplay::display(I);
      vpDisplay::flush(I);
      if (vpDisplay::getClick(I, false)) break;
      vpTime::wait(t, 1000. / g.getFramerate());
    }
  }
  catch(vpException e) {
    std::cout << e.getMessage() << std::endl;
  }
#else
  (void)argc;
  (void)argv;
  std::cout << "Install OpenCV or ffmpeg and rebuild ViSP to use this example." << std::endl;
#endif
}