YUV图片旋转

1、从H264视频流中解析出来的图片格式是YUV

　　YUV旋转可以选择手工旋转，也可以利用libYUV，libYUV开启NEON指令之后可以加快处理速度

　　在iOS系统上，利用Accelcerate库进行加速，其中旋转的方法是libYUV旋转的20倍

　　

    //测试YUV to RGBA 旋转然后 再到YUV 性能

    int width  = inFrame->width;
    int height = inFrame->height;
    int size   = width*height*4;
    uint8 *pRGBA = (uint8 *)calloc(size*3, sizeof(uint8));
    uint8 *pDstRGBA = (uint8 *)calloc(size*3, sizeof(uint8));

    start = [NSDate date];

    libyuv::I420ToARGB(inFrame->data[0],
                       inFrame->linesize[0],
                       inFrame->data[1],
                       inFrame->linesize[1],
                       inFrame->data[2],
                       inFrame->linesize[2],
                       pRGBA,
                       width*4,
                       width,
                       height);

    Pixel_8888 bgColor = {0,0,0,0};
    vImageRotate_ARGB8888((const vImage_Buffer *)pRGBA,
                          (const vImage_Buffer *)pDstRGBA,
                          NULL,
                          angle,
                          bgColor,
                          kvImageBackgroundColorFill);

    libyuv::ARGBToI420(pDstRGBA,
                       height*4,
                       _rotFrame->data[0],
                       _rotFrame->linesize[0],
                       _rotFrame->data[1],
                       _rotFrame->linesize[1],
                       _rotFrame->data[2],
                       _rotFrame->linesize[2],
                       width,
                       height);

    LOGE("YUV Rotate -[vImageRotate_ARGB8888] cost : %f", [[NSDate date] timeIntervalSinceDate:start]);

    free(pRGBA);
    free(pDstRGBA);