How to produce an Adobe DNG image from scratch with LibTiff

I am trying to generate an Adobe DNG file using libTiff from scratch for my specfic camera RAW files. For this I wrote an example to generate a DNG which should be completely black. However, i cannot open my result and i am suspecting that there is something wrong or something i missed in my code.

#include <stdlib.h>
#include <string.h>
#include <sys\stat.h>
#include <time.h>
#include <math.h>
#include <errno.h>  
#include <tiffio.h>

#define HPIXELS 2048            // number of horizontal pixels on PointGrey Grasshopper3 GS3-U3-41C6C sensor
#define VPIXELS 2048            // number of vertical pixels on PointGrey Grasshopper3 GS3-U3-41C6C sensor

int main(int argc, char **argv) {

    static const short CFARepeatPatternDim[] = { 2,2 }; // 2x2 CFA

    static const float cam_xyz[] = { 
        2.005, -0.771, -0.269, 
        -0.752, 1.688, 0.064, 
        -0.149, 0.283, 0.745 }; // xyz

    static const double sRGB[] = {
        3.6156, -0.8100, -0.0837,
        -0.3094, 1.5500, -0.5439,
        0.0967, -0.4700, 1.9805 }; // sRGB profile

    static const float neutral[] = { 0.807133, 1.0, 0.913289 };

    const int bpp = 8;
    const char* fname = "C:\\tmp\\dngTest\\output.DNG";

    long sub_offset = 0;
    long white = 0xffff;

    struct stat st;
    struct tm tm;
    char datetime[64];

    FILE *ifp;
    TIFF *tif;

    // ============================================================================
    stat(fname, &st);
    gmtime_s(&tm, &st.st_mtime);
    sprintf(datetime, "%04d:%02d:%02d %02d:%02d:%02d",
        tm.tm_year + 1900, tm.tm_mon + 1, tm.tm_mday, tm.tm_hour, tm.tm_min, tm.tm_sec);

    if (!(tif = TIFFOpen("C:\\tmp\\dngTest\\output.dng", "w"))) {
        fclose(ifp);
        exit(-1);
    }

    // Set meta data
    TIFFSetField(tif, TIFFTAG_SUBFILETYPE, 1);
    TIFFSetField(tif, TIFFTAG_IMAGEWIDTH,   HPIXELS >> 4);
    TIFFSetField(tif, TIFFTAG_IMAGELENGTH,  VPIXELS >> 4);
    TIFFSetField(tif, TIFFTAG_BITSPERSAMPLE, 8);
    TIFFSetField(tif, TIFFTAG_COMPRESSION, COMPRESSION_NONE);
    TIFFSetField(tif, TIFFTAG_PHOTOMETRIC, PHOTOMETRIC_RGB);
    TIFFSetField(tif, TIFFTAG_MAKE, "PointGrey");
    TIFFSetField(tif, TIFFTAG_MODEL, "Grasshopper3 GS3-U3-41C6C");
    TIFFSetField(tif, TIFFTAG_ORIENTATION, ORIENTATION_TOPLEFT);
    TIFFSetField(tif, TIFFTAG_SAMPLESPERPIXEL, 3);
    TIFFSetField(tif, TIFFTAG_PLANARCONFIG, PLANARCONFIG_CONTIG);
    TIFFSetField(tif, TIFFTAG_SOFTWARE, "primus_dng");
    TIFFSetField(tif, TIFFTAG_DATETIME, datetime);
    TIFFSetField(tif, TIFFTAG_SUBIFD, 1, &sub_offset);
    TIFFSetField(tif, TIFFTAG_DNGVERSION, "\001\001\0\0");
    TIFFSetField(tif, TIFFTAG_DNGBACKWARDVERSION, "\001\0\0\0");
    TIFFSetField(tif, TIFFTAG_UNIQUECAMERAMODEL, "PointGrey Grasshopper3 GS3-U3-41C6C");
    TIFFSetField(tif, TIFFTAG_COLORMATRIX1, 9, cam_xyz);
    TIFFSetField(tif, TIFFTAG_ASSHOTNEUTRAL, 3, neutral);
    TIFFSetField(tif, TIFFTAG_CALIBRATIONILLUMINANT1, 21);
    // TIFFSetField(tif, TIFFTAG_ORIGINALRAWFILENAME, fname); TODO enable when clear not to crash

    // All Black Thumbnail
    {
        unsigned char *buf = (unsigned char *)malloc((int)HPIXELS >> 4);
        memset(buf, 0, (int)HPIXELS >> 4);
        for (int row = 0; row < (int)VPIXELS>> 4; row++)
            TIFFWriteScanline(tif, buf, row, 0); // just leave it black, no software uses the built-in preview, builds off real image.
    }

    TIFFWriteDirectory(tif);


    // fprintf(stderr, "Writing TIFF header for main image...\n");
    TIFFSetField(tif, TIFFTAG_SUBFILETYPE, 0);          // image
    TIFFSetField(tif, TIFFTAG_IMAGEWIDTH, HPIXELS);     // in pixels
    TIFFSetField(tif, TIFFTAG_IMAGELENGTH, VPIXELS);    // in pixels
    TIFFSetField(tif, TIFFTAG_BITSPERSAMPLE, 16);       // int
    TIFFSetField(tif, TIFFTAG_PHOTOMETRIC, PHOTOMETRIC_CFA);
    TIFFSetField(tif, TIFFTAG_SAMPLESPERPIXEL, bpp);
    TIFFSetField(tif, TIFFTAG_PLANARCONFIG, PLANARCONFIG_CONTIG);
    TIFFSetField(tif, TIFFTAG_CFAREPEATPATTERNDIM, CFARepeatPatternDim);
    TIFFSetField(tif, TIFFTAG_CFAPATTERN, "\000\001\001\002"); // RGGB // 0 = Red, 1 = Green, 2 = Blue, 3 = Cyan, 4 = Magenta, 5 = Yellow, 6 = White 
    //TIFFSetField(tif, TIFFTAG_LINEARIZATIONTABLE, 256, curve); set it off for now
    TIFFSetField(tif, TIFFTAG_WHITELEVEL, 1, &white);

    fprintf(stderr, "Processing RAW data...\n");

    // bit depth
    unsigned char *pLine = (unsigned char*)malloc(sizeof(unsigned char) * HPIXELS);
    memset(pLine, 0, sizeof(unsigned char) * HPIXELS);
    for (int row = 0; row < VPIXELS; row++)
    {
        TIFFWriteScanline(tif, pLine, row, 0); // this writes a single complete row
    }
    free(pLine);
    TIFFClose(tif);
    return 0;
}

The minimal complete example is leaned on this. I am using a RGGB bayer battern. Switching to the Adobe DNG SDK is something I really want to avoid since building the libraries is a mess using VS2015 or higher.

The example program works as expected. I did a mistake on the bayer pattern which is actually GRGB and

TIFFSetField(tif, TIFFTAG_CFAPATTERN, "\001\000\001\002");