OpenCV HDR processing producing bad output on iOS

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I am trying to create an HDR image from 7 images taken with different exposure values on iOS. I used the OpenCV cocoapod and followed this GitHub repository to implement HDR processing. I have got the fusion image working and it has a decent picture output, however, the HDR version produces a bad output. It somewhat looks like the image is a negative version of what it should be.

Here is the image:

I have tried to mess around with my code to produce 8-bit and 32-bit versions of this image since that's what I read on some other questions.

I also included my HDR.cpp file that does the merging to HDR:

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

    // fusion
    // Mat fusion8bit;
    // fusion = fusion * 255;
    // fusion.convertTo(fusion8bit, CV_8U);
    // return fusion8bit;

    // hdr
    Mat hdr8bit;
    hdr = hdr * 255;
    hdr.convertTo(hdr8bit, CV_8U);
    return hdr8bit;
}

Let me know if you need any more of my code.