[gdal-dev] NITF2.1 complex data type

[Shawn Gong]

Hello Even,

To where can I submit the code?

Thanks,
Shawn
________________________________________
From: Even Rouault [even.rouault at spatialys.com]
Sent: March-26-15 12:52 PM
To: gdal-dev at lists.osgeo.org
Cc: Shawn Gong
Subject: Re: [gdal-dev] NITF2.1 complex data type

Shawn,

>
>
> We receive SAR SLC (single look complex) images in NITF2.1. But the I and O
> bands are separate (HH_I, HH_Q, VV_I, VV_Q, etc)
>
> My colleague modified the gdal NITF driver nitfdataset.cpp to rewrite them
> as NITFComplexRasterBand (see below) It works with a single-pol SLC and
> outputs as I+jQ. However dual- and quad-pol don't work. All three RGB
> bands show the same HH_I + j*HH_Q
>
> Are we doing it wrong, or NITF2.1 doesn't allow multi-pol Complex data
> type?

If you can read all the bands with the unmodified driver, then it comes from
your changes.

>
> Thanks,
> Shawn
> GDALDataset *NITFDataset::OpenInternal( GDALOpenInfo * poOpenInfo,
>                                 GDALDataset *poWritableJ2KDataset,
>                                 int bOpenForCreate)
> {
> .....
> .....
>
>     GDALDataType dt = bandList[0]->GetRasterDataType();
>     if (EQUAL(psImage->szICAT,"SAR")    //SAR image...
>         && nUsableBands==psImage->nBands && nUsableBands%2==0     //...with
> 2 bands ... (modified to allow an even number - spec seems to indicate
> only 2 bands allowed?) && dt==bandList[1]->GetRasterDataType()   //...that
> have the same datatype... && !GDALDataTypeIsComplex(dt)   //...and are not
> complex... && (dt==GDT_Int16 || dt==GDT_Int32 || dt==GDT_Float32 ||
> dt==GDT_Float64))      //..and can be mapped directly to a complex type {
>   bool allBandsIQ = true;
>   for (int i = 0; i < nUsableBands; i+=2)
>   {
>    NITFBandInfo *psBandInfo1 = psImage->pasBandInfo + i;
>    NITFBandInfo *psBandInfo2 = psImage->pasBandInfo + i + 1;
>    //check that the ISUBCAT is labelled "I" and "Q" on the 2 bands
>    if (!EQUAL(psBandInfo1->szISUBCAT, "I") ||
> !EQUAL(psBandInfo2->szISUBCAT, "Q")) {
>     allBandsIQ = false;
>     break;
>    }
>   }
>   if (allBandsIQ)
>   {
>    nUsableBands /= 2;
>    for (int i = 0; i < nUsableBands; i++)
>    {
>     //wrap the I and Q bands into a single complex band
>     bandList[i] = new NITFComplexRasterBand(poDS, bandList[2 * i],
> bandList[2 * i + 1], i+1); }

-->This looks a bit suspicious as you're modifying the array you're iterating
over, but I think that must be still be OK, although as you show only part of
the code, it is difficult to tell for sure.

Best regards,

Even

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