颜色转换rgb24 to yuv420

 void CVideoEncoder::RGB24ToYUV420(int Width,int Height,uint8_t* RgbBuffer,uint8_t*YuvBuffer)
 {
     uint8_t* yuvBuf=YuvBuffer;//YUV空间
     int nWidth=Width;
     int nHeight=Height;
     /下面转换算法是网上查到的
     int i, j;
     uint8_t*bufY = yuvBuf;
     uint8_t*bufU = yuvBuf + nWidth * nHeight;
     uint8_t*bufV = bufU + (nWidth* nHeight* 1/4);
     uint8_t*Y=bufY;
     uint8_t*U=bufU;
     uint8_t*V=bufV;
     uint8_t*bufRGB;
     unsigned char y, u, v, r, g, b,testu,testv;
     if (NULL==pRGBBuffer)
     {
        return ;
     }
     for (j = 0; j
     {
         bufRGB = RgbBuffer + nWidth * (nHeight - 1-j) * 3 ;
         for (i = 0;i
         {
             int pos = nWidth * i + j;
             r= *(bufRGB++);
             g = *(bufRGB++);
             b = *(bufRGB++);
             y =(unsigned char)(( 66 * r + 129 * g +  25 * b + 128) >>8) + 16;//16
             v = (unsigned char)((-38 * r -  74 * g + 112 * b + 128) >>8) +128  ; //128
             u = (unsigned char)((112 * r -  94 * g -  18 * b + 128) >> 8) + 128 ;
             *(bufY++)=max(0,min(y, 255 ));

             if (j%2==0&&i%2 ==0)
             {
                 if (u>255)
                 {
                     u=255;
                 }
                 if (u<0)
                 {
                     u = 0;
                 }
                 *(bufU++) =u;
                 //存u分量
             }
             else
             {
                 //存v分量
                 if (i%2==0)
                 {
                     if (v>255)
                     {
                         v = 255;
                     }
                     if (v<0)
                     {
                         v = 0;
                     }
                     *(bufV++) =v;
                 }
             }
         }
     }
 }

 //YUV对应到data
             pVideoEncoder->m_pYUVFrame->data[0]=pVideoEncoder->yuv_buff;
             pVideoEncoder->m_pYUVFrame->data[1]=pVideoEncoder->yuv_buff+y_size;
             pVideoEncoder->m_pYUVFrame->data[2]=pVideoEncoder->yuv_buff+(y_size*5)/4;

 //第二种方法 用FFMPEG
 uint8_t *rgb_src[3]= {rgb, NULL, NULL};
 int rgb_stride[3]={3*biWidth, 0, 0};
 AVFrame picture;
 avpicture_alloc((AVPicture*)(&picture), AV_PIX_FMT_YUV420P,biWidth,biHeight);
 SwsContext *yuvContext=sws_getContext(biWidth,biHeight,AV_PIX_FMT_BGR24,biWidth,
 biHeight,AV_PIX_FMT_YUV420P,SWS_BICUBIC, NULL, NULL, NULL);
 sws_scale(yuvContext,rgb_src, rgb_stride, 0, biHeight, picture.data, picture.linesize);

//注意 如果转换后出现倒立，请安下面方式更正

 picture.data[0] += picture.linesize[0] * (biHeight - 1);
 picture.linesize[0] *= -1;
 picture.data[1] += picture.linesize[1] * (biHeight / 2 - 1);
 picture.linesize[1] *= -1;
 picture.data[2] += picture.linesize[2] * (biHeight/ 2 - 1);
 picture.linesize[2] *= -1;