HFARasterBand::GetColorInterpretation can't report RGB colorspace

[mrosen]

HFARasterBand::GetColorInterpretation? can't report RGB colorspace.

I'm attaching two files to illustrate the issue

• an AUX file for an RGB image.
• an IMG file for a grayscale image.

In both cases gdalinfo reports ColorInterp?=Undefined for all bands. Using the fix below, the bands are reported correctly. ==========================

/************************************************************************/
/*                       GetColorInterpretation()                       */
/************************************************************************/

GDALColorInterp HFARasterBand::GetColorInterpretation()

{
    HFADataset *poHDS = (HFADataset *) poDS;
    if (poHDS->nBands == 3)
    {
        switch (nBand)
        {
          case 1: return GCI_BlueBand;
          case 2: return GCI_GreenBand;
          case 3: return GCI_RedBand;
        }
    }
    else if (poCT != NULL)
    {
        return GCI_PaletteIndex;
    }
    else if (poHDS->nBands == 1) return GCI_GrayIndex;
    return GCI_Undefined;
    /*
    if( poCT != NULL )
        return GCI_PaletteIndex;
    else
        return GCI_Undefined;
    */
}

[mrosen]

rgb aux file

[mrosen]

the IMG file was too big to attach. see me if you need it. the patch is pretty straightforward though.

[rouault]

Is there a reason considering that a 3 band should be always interpreted as RGB ?

[mrosen]

In general, it seems like it's more right than wrong. I imagine there are cases where is this wrong (BGR and NIR-G-B come to mind -- though I don't know if there are such HFA files in practice).

It would be great if the driver could read metadata to ensure that colorinterp is reported correctly... but I could not see how that would work. Absent that, I think that assuming a 3 band image is RGB is a better choice than saying it's undefined ... at least it was for cases we were dealing with ;-).