12/23/2014

yuv422(YUYV) to RGB and RGB to yuv422(YUYV), (Using OpenCV and TBB)

In past, I wrote an articel about YUV 444, 422, 411 introduction and yuv <-> rgb converting example code.
refer to this page -> http://feelmare.blogspot.kr/2012/11/yuv-color-format-444-422-411-simple.html

In this article, I will introduce method of using opencv and TBB.
TBB is an acronym for Thread Building Block.
TBB is to enable parellel processing using multi thread.
see the this page -> http://feelmare.blogspot.kr/2014/12/opencv-tbb-utility-parallelfor.html


This is YUV422 to RGB example source code.
In my case YUV422 is consisted of YUYV.
And input type of the YUYV data is unsigned char *.

So example is
unsigned char * yuyv to Mat rgb
In here, m_stride is real width length of yuyv data.

....
Mat yuyv(m_height, m_width, CV_8UC2);
memcpy( yuyv.data, yuyv_buffer, sizeof(unsigned char) * (m_stride * m_height) );
Mat rgb(m_height, m_width, CV_8UC3);
cvtColor(yuyv, rgb, CV_YUV2BGR_YUYV);
....



Next example is rgb to yuyv using TBB.
....
class Parallel_process : public cv::ParallelLoopBody
{

private:
 cv::Mat& inImg;
 unsigned char* outImg;
 int widhStep;
 int m_stride;

public:
 Parallel_process(cv::Mat& inputImgage,  unsigned char* outImage)
  : inImg(inputImgage), outImg(outImage){

   widhStep = inputImgage.size().width * 3; 
   m_stride = inputImgage.size().width *2;

 }

 virtual void operator()(const cv::Range& range) const
 {
  //thread
  for(int i = range.start; i < range.end; i++)
  {

   int s1 = i*widhStep;

   for(int iw=0; iw< inImg.size().width; iw=iw+2)
   {
    int s2 = iw*3;

    int mc = s1+s2;
    int B1 = (unsigned char)(inImg.data[mc + 0]);
    int G1 = (unsigned char)(inImg.data[mc + 1]);
    int R1 = (unsigned char)(inImg.data[mc + 2]);
    int B2 = (unsigned char)(inImg.data[mc + 3]);
    int G2 = (unsigned char)(inImg.data[mc + 4]);
    int R2 = (unsigned char)(inImg.data[mc + 5]);


    int Y = (0.257*R1) + (0.504*G1) + (0.098*B1) +16;
    int U = -(0.148*R1) - (0.291*G1) + (0.439*B1) + 128;
    int V = (0.439*R1 ) - (0.368*G1) - (0.071*B1) + 128;
    int Y2 = (0.257*R2) + (0.504*G2) + (0.098*B2) +16;

    Y = MMIN(255, MMAX(0, Y));
    U = MMIN(255, MMAX(0, U));
    V = MMIN(255, MMAX(0, V));
    Y2 = MMIN(255, MMAX(0, Y2)); 

    mc = i*m_stride + iw*2;
    outImg[mc + 0] = Y;
    outImg[mc + 1] = U;
    outImg[mc + 2] = Y2;
    outImg[mc + 3] = V;

   }
  }
 }
};



//in main rutine
cv::parallel_for_(cv::Range(0, (OriginMat).rows), Parallel_process((OriginMat), inP_OriginImg));

....


In opencv convert function,  YUYV to RGB option is exist (-> CV_YUV2BGR_YUYV).
But RGB to YUYV option is not exist.

thank you.

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