VideoCapture类提供了各项视频操作,目前opencv只支持avi格式,而且无声音,编解码一般为4字符,即XVID, DIVX or H264
获取编码code类型
VideoCapture inputVideo(source); // Open input int ex = static_cast<int>(inputVideo.get(CV_CAP_PROP_FOURCC)); // Get Codec Type- Int form然后将整数转换成字符convert from the integer form to string
char EXT[] = {ex & 0XFF , (ex & 0XFF00) >> 8,(ex & 0XFF0000) >> 16,(ex & 0XFF000000) >> 24, 0};
//You can do the same thing with the union as: union { int v; char c[5];} uEx ; uEx.v = ex; // From Int to char via union uEx.c[4]=’\0’;
打开摄像头或读取本地视频文件
VideoCapture cam(0);//打开摄像头 VideoCapture cam("a.avi");//打开本地文件
if ( !cam.isOpened()) { cout << "Could not open reference " << sourceReference << endl; return -1; }
cam>>frame; cam.read(frame);注意:使用read方法时,即使没有帧传过来也会读取;这时需用frame.empty判断;而>>不需要判断。
获取视频size
Size refS = Size((int) cam.get(CV_CAP_PROP_FRAME_WIDTH),(int) cam.get(CV_CAP_PROP_FRAME_HEIGHT)),
captRefrnc.set(CV_CAP_PROP_POS_MSEC, 1.2); // go to the 1.2 second in the video captRefrnc.set(CV_CAP_PROP_POS_FRAMES, 10); // go to the 10th frame of the video
写视频
outputVideo.write(res); //or outputVideo << res;
split(src, spl); // process - extract only the correct channel for( int i =0; i < 3; ++i) if (i != channel) spl[i] = Mat::zeros(S, spl[0].type()); merge(spl, res);
#include <iostream> // for standard I/O #include <string> // for strings #include <iomanip> // for controlling float print precision #include <sstream> // string to number conversion #include <opencv2/core/core.hpp> // Basic OpenCV structures (cv::Mat, Scalar) #include <opencv2/imgproc/imgproc.hpp> // Gaussian Blur #include <opencv2/highgui/highgui.hpp> // OpenCV window I/O using namespace std; using namespace cv; double getPSNR ( const Mat& I1, const Mat& I2);//获取峰值信噪比 Scalar getMSSIM( const Mat& I1, const Mat& I2);//平均结构相似度 static void help() { cout << "------------------------------------------------------------------------------" << endl << "This program shows how to read a video file with OpenCV. In addition, it " << "tests the similarity of two input videos first with PSNR, and for the frames " << "below a PSNR trigger value, also with MSSIM." << endl << "Usage:" << endl << "./video-source referenceVideo useCaseTestVideo PSNR_Trigger_Value Wait_Between_Frames " << endl << "--------------------------------------------------------------------------" << endl << endl; } int main(int argc, char *argv[]) { help(); int psnrTriggerValue, delay; psnrTriggerValue=10; delay=100; char c; int frameNum = -1; // Frame counter VideoCapture captRefrnc("2.avi"), captUndTst("3.avi"); if (!captRefrnc.isOpened()) { cout << "Could not open reference " << endl; return -1; } if (!captUndTst.isOpened()) { cout << "Could not open case test " << endl; return -1; } Size refS = Size((int) captRefrnc.get(CV_CAP_PROP_FRAME_WIDTH), (int) captRefrnc.get(CV_CAP_PROP_FRAME_HEIGHT)), uTSi = Size((int) captUndTst.get(CV_CAP_PROP_FRAME_WIDTH), (int) captUndTst.get(CV_CAP_PROP_FRAME_HEIGHT)); if (refS != uTSi) { cout << "Inputs have different size!!! Closing." << endl; return -1; } const char* WIN_UT = "Under Test"; const char* WIN_RF = "Reference"; // Windows namedWindow(WIN_RF, CV_WINDOW_AUTOSIZE); namedWindow(WIN_UT, CV_WINDOW_AUTOSIZE); cvMoveWindow(WIN_RF, 400 , 0); //750, 2 (bernat =0) cvMoveWindow(WIN_UT, refS.width, 0); //1500, 2 cout << "Reference frame resolution: Width=" << refS.width << " Height=" << refS.height << " of nr#: " << captRefrnc.get(CV_CAP_PROP_FRAME_COUNT) << endl; cout << "PSNR trigger value " << setiosflags(ios::fixed) << setprecision(3) << psnrTriggerValue << endl; Mat frameReference, frameUnderTest; double psnrV; Scalar mssimV; for(;;) //Show the image captured in the window and repeat { captRefrnc >> frameReference; captUndTst >> frameUnderTest; if (frameReference.empty() || frameUnderTest.empty()) { cout << " < < < Game over! > > > "; break; } ++frameNum; cout << "Frame: " << frameNum << "# "; ///////////////////////////////// PSNR //////////////////////////////////////////////////// psnrV = getPSNR(frameReference,frameUnderTest); cout << setiosflags(ios::fixed) << setprecision(3) << psnrV << "dB"; //////////////////////////////////// MSSIM ///////////////////////////////////////////////// if (psnrV < psnrTriggerValue && psnrV) { mssimV = getMSSIM(frameReference, frameUnderTest); cout << " MSSIM: " << " R " << setiosflags(ios::fixed) << setprecision(2) << mssimV.val[2] * 100 << "%" << " G " << setiosflags(ios::fixed) << setprecision(2) << mssimV.val[1] * 100 << "%" << " B " << setiosflags(ios::fixed) << setprecision(2) << mssimV.val[0] * 100 << "%"; } cout << endl; ////////////////////////////////// Show Image ///////////////////////////////////////////// imshow(WIN_RF, frameReference); imshow(WIN_UT, frameUnderTest); c = (char)cvWaitKey(delay); if (c == 27) break; } return 0; } double getPSNR(const Mat& I1, const Mat& I2) { Mat s1; absdiff(I1, I2, s1); // |I1 - I2| s1.convertTo(s1, CV_32F); // cannot make a square on 8 bits s1 = s1.mul(s1); // |I1 - I2|^2 Scalar s = sum(s1); // sum elements per channel double sse = s.val[0] + s.val[1] + s.val[2]; // sum channels if( sse <= 1e-10) // for small values return zero return 0; else { double mse = sse / (double)(I1.channels() * I1.total()); double psnr = 10.0 * log10((255 * 255) / mse); return psnr; } } Scalar getMSSIM( const Mat& i1, const Mat& i2) { const double C1 = 6.5025, C2 = 58.5225; /***************************** INITS **********************************/ int d = CV_32F; Mat I1, I2; i1.convertTo(I1, d); // cannot calculate on one byte large values i2.convertTo(I2, d); Mat I2_2 = I2.mul(I2); // I2^2 Mat I1_2 = I1.mul(I1); // I1^2 Mat I1_I2 = I1.mul(I2); // I1 * I2 /*************************** END INITS **********************************/ Mat mu1, mu2; // PRELIMINARY COMPUTING GaussianBlur(I1, mu1, Size(11, 11), 1.5); GaussianBlur(I2, mu2, Size(11, 11), 1.5); Mat mu1_2 = mu1.mul(mu1); Mat mu2_2 = mu2.mul(mu2); Mat mu1_mu2 = mu1.mul(mu2); Mat sigma1_2, sigma2_2, sigma12; GaussianBlur(I1_2, sigma1_2, Size(11, 11), 1.5); sigma1_2 -= mu1_2; GaussianBlur(I2_2, sigma2_2, Size(11, 11), 1.5); sigma2_2 -= mu2_2; GaussianBlur(I1_I2, sigma12, Size(11, 11), 1.5); sigma12 -= mu1_mu2; ///////////////////////////////// FORMULA //////////////////////////////// Mat t1, t2, t3; t1 = 2 * mu1_mu2 + C1; t2 = 2 * sigma12 + C2; t3 = t1.mul(t2); // t3 = ((2*mu1_mu2 + C1).*(2*sigma12 + C2)) t1 = mu1_2 + mu2_2 + C1; t2 = sigma1_2 + sigma2_2 + C2; t1 = t1.mul(t2); // t1 =((mu1_2 + mu2_2 + C1).*(sigma1_2 + sigma2_2 + C2)) Mat ssim_map; divide(t3, t1, ssim_map); // ssim_map = t3./t1; Scalar mssim = mean(ssim_map); // mssim = average of ssim map return mssim; }