QImage转yuv420

void RGB24ToYUV420(int Width,int Height,uint8_t* pRGBBuffer,uint8_t*pYuvBuffer)
{
    uint8_t* yuvBuf=pYuvBuffer;//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<nHeight;j++)
    {
        bufRGB = pRGBBuffer + nWidth * (nHeight - 1-j) * 3 ;
        for (i = 0;i<nWidth;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;
                }
            }
        }
    }
    //    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;

}

注意的是：QImage一定要转成Format_RGB888格式，否则会出现错误，倒立等情况

void SaveObject::acceptData(QImage t_image,int w,int h)
 {
 t_image = t_image.convertToFormat(QImage::Format_RGB888);