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High Dynamic Range Imaging using openCV on iOS producing bad output

I've asked this question at on stack overflow but maybe someone in the openCV community has come across the same issue:

I'm trying to use openCV 3 on iOS to produce an HDR image from multiple exposures that will eventually be output as an EXR file. I noticed I was getting garbled output when I tried to create an HDR image. Thinking it was a mistake in trying to create a camera response, I started from scratch and adapted the HDR imaging tutorial material on the openCV to iOS but it produces similar results. The following C++ code returns a garbled image:

cv::Mat mergeToHDR (vector<Mat>& images, vector<float>& times)
    imgs = images;
    Mat response;
    //Ptr<CalibrateDebevec> calibrate = createCalibrateDebevec();
    //calibrate->process(images, response, times);

    Ptr<CalibrateRobertson> calibrate = createCalibrateRobertson();
    calibrate->process(images, response, times);

    // create HDR
    Mat hdr;
    Ptr<MergeDebevec> merge_debevec = createMergeDebevec();
    merge_debevec->process(images, hdr, times, response);

    // create LDR
    Mat ldr;
    Ptr<TonemapDurand> tonemap = createTonemapDurand(2.2f);
    tonemap->process(hdr, ldr);

    // create fusion
    Mat fusion;
    Ptr<MergeMertens> merge_mertens = createMergeMertens();
    merge_mertens->process(images, fusion);

    Uncomment what kind of tonemapped image or hdr to return
    Returning one of the images in the array produces ungarbled output
    so we know the problem is unlikely with the openCV to UIImage conversion

    //give back one of the images from the image array
    //return images[0];

    //give back one of the hdr images
    return fusion * 255;
    //return ldr * 255;
    //return hdr

This is what the image looks like:

Bad image

I've analysed the image, tried various colour space conversions, but the data appears to be junk.

The openCV framework is the latest compiled 3.0.0 version from the website. The RC and alpha produce the same results, and the current version won't build (for iOS or OSX). I was thinking my next steps would be to try and get the framework to compile from scratch, or to get the example working under another platform to see if the issue is platform specific or with the openCV HDR functions themselves. But before I do that I thought I would throw the issue up on stack overflow to see if anyone had come across the same issue or if I am missing something blindingly obvious.

I have uploaded the example xcode project to here:

The HDR tutorial from openCV:

Getting openCV to work with swift was with the help from user foundry on github