OpenCV学习笔记（5）在单个窗口中显示多个视频子窗口

转自http://blog.csdn.net/chenyusiyuan/article/details/4642297

参考OpenCV中文论坛的一个帖子（http://www.opencv.org.cn/forum/viewtopic.php?f=1&t=7996&start=0）实现了在一个窗口显示多个视频子窗口，能够读入单个的视频或摄像头数据，然后在一个窗口中分别显示原始帧图像、反色图像、灰度图像以及Canny边缘检测图像。并在每个子窗口左上角显示系统时间，函数cvShowManyImages是改写的。

代码如下：

#include "stdafx.h" #include <cv.h> #include <cxcore.h> #include <highgui.h> #include <stdio.h> #include <stdarg.h>#include <time.h> // 隐藏 console 窗口 #pragma comment( linker, "/subsystem:/"windows/" /entry:/"mainCRTStartup/"" ) // 单窗口显示多幅图像的函数 void cvShowMultiImages(char* title, int nArgs, ...) { // img - Used for getting the arguments IplImage* img; // DispImage - the image in which all the input images are to be copied IplImage*DispImage; int size; // size - the size of the images in the window int ind; // ind - the index of the image shown in the window int x, y; // x,y - the coordinate of top left coner of input images int w, h; // w,h - the width and height of the image // r - Maximum number of images in a column // c - Maximum number of images in a row int r, c;// scale - How much we have to resize the image float scale; // max - Max value of the width and height of the image int max; // space - the spacing between images int space; // If the number of arguments is lesser than 0 or greater than 12 // return without displaying if(nArgs <= 0) { printf("Number of arguments too small..../n");return; } else if(nArgs > 12) { printf("Number of arguments too large..../n"); return; } // Determine the size of the image, // and the number of rows/cols // from number of arguments else if (nArgs == 1) { r = c = 1; size = 300; } else if (nArgs == 2) { r = 2; c = 1; size = 300; } else if (nArgs == 3 || nArgs == 4) { r = 2; c = 2; size = 300; } else if (nArgs == 5 || nArgs == 6) { r = 3; c = 2; size = 200; } else if (nArgs == 7 || nArgs == 8) { r = 4; c =2; size = 200; } else { r = 4; c = 3; size = 150; } // Create a new 3 channel image to show all the input imagesDispImage = cvCreateImage( cvSize(60 + size*r, 20 + size*c), IPL_DEPTH_8U, 3 ); // Used to get the arguments passedva_list args; va_start(args, nArgs); // Loop for nArgs number of arguments space = 20; for (ind = 0, x = space, y =space; ind < nArgs; ind++, x += (space + size)) { // Get the Pointer to the IplImage img = va_arg(args, IplImage*);// Check whether it is NULL or not // If it is NULL, release the image, and return if(img == 0) { printf("Invalid arguments"); cvReleaseImage(&DispImage); return; } // Find the width and height of the image w = img->width; h =img->height; // Find whether height or width is greater in order to resize the image max = (w > h)? w: h; // Find the scaling factor to resize the image scale = (float) ( (float) max / size ); // Used to Align the images // i.e. Align the image to next row if( ind % r == 0 && x!= space) { x = space; y += space + size; } // Set the image ROI to display the current image cvSetImageROI(DispImage, cvRect(x, y, (int)( w/scale ), (int)( h/scale ))); // Resize the input image and copy the it to the Single Big Image cvResize(img, DispImage); // Reset the ROI in order to display the next image cvResetImageROI(DispImage); } // Create a new window, and show the Single Big Image//cvNamedWindow( title, 1 ); cvShowImage( title, DispImage); // End the number of arguments va_end(args); //Release the Image Memory cvReleaseImage(&DispImage); } int main( int argc, char** argv ) { CvCapture* capture; if(argc == 1) { capture = cvCreateCameraCapture( 0 ); } else { capture = cvCreateFileCapture( argv[1] ); } IplImage*frame; cvNamedWindow("video",1); cvResizeWindow("video",750,750); CvFont timeFont,timeFont1; cvInitFont(&timeFont, CV_FONT_HERSHEY_COMPLEX, 1.0f,1.0f,0,1,8); cvInitFont(&timeFont1, CV_FONT_HERSHEY_COMPLEX, 1.0f,1.0f,0,1,8); //Initialize new applied memory of 'time1' char timestr[25]; memset(timestr, 0, 25 * sizeof(char)); while (1) { frame= cvQueryFrame( capture ); if (!frame) break; // Get the systme local time info time_t rawtime; struct tm*timeinfo; //time( &rawtime ); rawtime = time( NULL ); timeinfo = localtime( &rawtime ); char* p = asctime( timeinfo ); // the 25th character of array 'p' is '/n' // but it can not be display correctly in the image // so we just read out the first 24 character of 'p' for (int i = 0; i < 24; i++) { timestr[i] = *p; p++; } p = NULL; // Bitwise inversion of every element of the current frame IplImage* frame_not = cvCreateImage(cvGetSize(frame),frame->depth,frame->nChannels); cvNot(frame,frame_not); // Get the gray scale image of the current frmae // and transform the gray image from single channel to three channels IplImage* frame_gray=cvCreateImage(cvGetSize(frame),frame->depth,1); IplImage* frame1=cvCreateImage(cvGetSize(frame),frame->depth,frame->nChannels); cvCvtColor(frame,frame_gray,CV_RGB2GRAY); cvCvtColor(frame_gray,frame1,CV_GRAY2BGR); // Do Canny edge detection //and transform the result image from single channel to three channels IplImage*frame_canny=cvCreateImage(cvGetSize(frame),frame->depth,1); IplImage* frame2=cvCreateImage(cvGetSize(frame),frame->depth,frame->nChannels); cvCanny(frame_gray,frame_canny,20,75,3); cvCvtColor(frame_canny,frame2,CV_GRAY2BGR); //Display the local time information in each image cvPutText( frame, timestr, cvPoint(5,25), &timeFont, CV_RGB(255,0,0) ); cvPutText( frame1, timestr, cvPoint(5,25), &timeFont, CV_RGB(255,0,0) ); cvPutText( frame2, timestr, cvPoint(5,25), &timeFont1, CV_RGB(255,0,0) ); cvPutText( frame_not, timestr, cvPoint(5,25), &timeFont1, CV_RGB(255,0,0) ); cvShowMultiImages("video",4,frame,frame_not,frame1,frame2); //cvWaitKey(33); int key =cvWaitKey(33); if( key == 27 ) break; cvReleaseImage(&frame_not); cvReleaseImage(&frame1); cvReleaseImage(&frame_gray); cvReleaseImage(&frame2); cvReleaseImage(&frame_canny); } cvDestroyWindow("video"); cvReleaseCapture(&capture); return 0; }

有几点需要注意： 
1、在 while 循环中，处理完的图像应及时释放所占用的内存（cvReleaseImage），否则会不断占用内存空间以致系统当机。 
2、图像数据的指针若是由 cvCreateImage 返回的，则应由 cvReleaseImage 来释放内存；如果是读取自视频或摄像头的帧图像，则应用 cvReleaseCapture 来释放内存，不必再用 cvReleaseImage() ，在 while 循环中使用 cvReleaseImage( &frame )  会导致生成的程序在执行时出错。 
3、有关va_list、va_start、va_arg、va_end的原理与使用，参见http://www.cppblog.com/qiujian5628/archive/2008/01/21/41562.html