3.使用例2-10中的视频捕捉和存储方法，结合例2-5中的doPyrDown()创建一个程序,使其从摄像机读入视频数据并将缩放变换后的彩色图像存入磁盘。
例2-10中所用的方法虽然能正常运行，但却不能生成存储的视频，百思不得其解。遂参考了一篇博文：blog.csdn.net/jacke121/article/details/54607863
利用文中的方法实现了上述功能。代码如下
1 /*ch2_lx2_3.cpp 2017/11/29 2 本程序是learning opencv这本书的课后习题练习 3 欢迎提出问题一起讨论*/ 4 #include "cv.h" 5 #include "highgui.h" 6 using namespace std; 7 IplImage* doPyrDown( 8 IplImage* in, 9 int filter = IPL_GAUSSIAN_5x5) 10 { 11 assert(in->width%2 == 0 && in->height%2 == 0); 12 13 IplImage* out = cvCreateImage( 14 cvSize( in->width/2, in->height/2 ), 15 in->depth, 16 in->nChannels 17 ); 18 cvPyrDown(in,out); 19 return(out); 20 }; 21 int main( int argc, char** argv ) 22 { 23 cvNamedWindow( "Example2",CV_WINDOW_AUTOSIZE); 24 cvNamedWindow( "Example3",CV_WINDOW_AUTOSIZE); 25 CvCapture* capture = cvCreateFileCapture(argv[1]); 26 IplImage* frame; 27 IplImage* img; 28 CvVideoWriter *video=NULL; 29 int i=0; 30 int n; 31 while(1) 32 { 33 frame = cvQueryFrame( capture ); 34 img = doPyrDown( frame ); 35 if( !frame ) break; 36 37 if(i==0) 38 video=cvCreateVideoWriter("camera.avi",CV_FOURCC('X', 'V', 'I', 'D'),25,cvSize(img->width,img->height)); 39 if(video) 40 { 41 cout<<"video writer has created!"<<endl; 42 } 43 n=cvWriteFrame(video,img); 44 printf("cvWriteFrame %d ", n); 45 i++; 46 cout<<n<<endl; 47 cvShowImage( "Example2", frame ); 48 cvShowImage( "Example3", img ); 49 char c = cvWaitKey(33); 50 if( c == 27 ) break; 51 52 } 53 cvReleaseImage(&frame); 54 cvReleaseImage(&img); 55 cvReleaseVideoWriter(&video); 56 cvReleaseCapture( &capture ); 57 cvDestroyWindow( "Example2" ); 58 return 0; 59 }