Error in CvtColor code, wrong channel identified as blue (Bugfix #3121)

It would be great if somebody could work on a pull request...

The example works fine with the current version of OpenCV. Probably OpenCV doesn't contain the bug but code isn't very clear. Need to investigate the problem deeply.

#include <opencv2/opencv.hpp>
#include <opencv2/imgproc/types_c.h>
#include <iostream>
#include <string>

int main(int argc, char* argv[])
{
    if (argc < 2)
    {
        std::cout << "Usage: " << argv[0] << " <image>" << std::endl;
        return -1;
    }

    std::string name = argv[1];
    cv::Mat bgr = cv::imread(name), rgb, yuv;

    cv::cvtColor(bgr, yuv, CV_BGR2YUV);

    cv::cvtColor(yuv, rgb, CV_YUV2RGB);
    cv::cvtColor(rgb, bgr, CV_RGB2BGR);

    cv::namedWindow("bgr");
    cv::imshow("bgr", bgr);

    cv::waitKey();
    return 0;
}