1. unsigned char* BGR2NV21(cv::Mat& Img,int Width,int Height)
    2. {
    3.     int cols = Width;
    5.     int rows = Height;
    7.     int Yindex = 0;
    9.     int UVindex = rows * cols;
    10.     int isize = 1.5 * rows * cols;
    11.     unsigned char* yuvbuff = new unsigned char[isize];
    13.     cv::Mat NV21(rows + rows / 2, cols, CV_8UC1);
    15.     for (int i = 0; i<rows; i++)
    17.     {
    19.         for (int j = 0; j<cols; j++)
    21.         {
    22.             uchar* YPointer = NV21.ptr<uchar>(i);
    24.             int B = Img.at<cv::Vec3b>(i, j)[0];
    26.             int G = Img.at<cv::Vec3b>(i, j)[1];
    28.             int R = Img.at<cv::Vec3b>(i, j)[2];
    30.             //计算Y的值
    31.             int Y = (77 * R + 150 * G + 29 * B) >> 8;
    33.             YPointer[j] = Y;
    35.             yuvbuff[Yindex++] = (Y < 0) ? 0 : ((Y > 255) ? 255 : Y);
    37.             uchar* UVPointer = NV21.ptr<uchar>(rows + i / 2);
    39.             //计算U、V的值，进行2x2的采样
    40.             if (i % 2 == 0 && (j) % 2 == 0)
    41.             {
    42.                 int U = ((-44 * R - 87 * G + 131 * B) >> 8) + 128;
    44.                 int V = ((131 * R - 110 * G - 21 * B) >> 8) + 128;
    46.                 UVPointer[j] = V;
    48.                 UVPointer[j + 1] = U;
    50.                 yuvbuff[UVindex++] = (V < 0) ? 0 : ((V > 255) ? 255 : V);
    52.                 yuvbuff[UVindex++] = (U < 0) ? 0 : ((U > 255) ? 255 : U);
    54.             }
    56.         }
    58.     }
    59.     return yuvbuff;
    60. }