某些特定场合我们会经常遇到yuv420格式的视频文件，这种视频帧无法直接用于OpenCV，故而，需要进行格式转换；幸运的是，opencv提供了rgb到yuv420的格式转换函数；下面给出基本用法；
函数1：读取avi格式的视频文件，转换成Yuv420格式，并写入文件；
void WriteYuv() { cv::VideoCapture vc; bool flag = vc.open("S1000008.avi"); if (!flag) { printf("avi file open error \n"); system("pause"); exit(-1); } int frmCount = vc.get(CV_CAP_PROP_FRAME_COUNT); frmCount -= 5; printf("frmCount: %d \n", frmCount); int w = vc.get(CV_CAP_PROP_FRAME_WIDTH); int h = vc.get(CV_CAP_PROP_FRAME_HEIGHT); int bufLen = w*h*3/2; unsigned char* pYuvBuf = new unsigned char[bufLen]; FILE* pFileOut = fopen("result.yuv", "w+"); if (!pFileOut) { printf("pFileOut open error \n"); system("pause"); exit(-1); } printf("pFileOut open ok \n"); for (int i=0; i<frmCount; i++) { printf("%d/%d \n", i+1, frmCount); cv::Mat srcImg; vc>>srcImg; cv::imshow("img", srcImg); cv::waitKey(1); cv::Mat yuvImg; cv::cvtColor(srcImg, yuvImg, CV_BGR2YUV_I420); memcpy(pYuvBuf, yuvImg.data, bufLen*sizeof(unsigned char)); fwrite(pYuvBuf, bufLen*sizeof(unsigned char), 1, pFileOut); } fclose(pFileOut); delete[] pYuvBuf; }
函数二，读取yuv420格式的文件，转换成cv::Mat格式，并予以显示：
void DisplayYUV() { int w = 1280; int h = 720; printf("yuv file w: %d, h: %d \n", w, h); FILE* pFileIn = fopen("result.yuv", "rb+"); int bufLen = w*h*3/2; unsigned char* pYuvBuf = new unsigned char[bufLen]; int iCount = 0; for(int i=0; i<200; i++) { fread(pYuvBuf, bufLen*sizeof(unsigned char), 1, pFileIn); cv::Mat yuvImg; yuvImg.create(h*3/2, w, CV_8UC1); memcpy(yuvImg.data, pYuvBuf, bufLen*sizeof(unsigned char)); cv::Mat rgbImg; cv::cvtColor(yuvImg, rgbImg, CV_YUV2BGR_I420); cv::imshow("img", yuvImg); cv::waitKey(1); printf("%d \n", iCount++); } delete[] pYuvBuf; fclose(pFileIn); }
