[Gdal-dev] How to set a ColorTable from scratch?

[Frank Warmerdam]

Joaquim Luis wrote:
> Hi,
> I finally learned how to use the Create() method. However, I didn't find 
> out how to create a new colortable.
> There is the GDALSetRasterColorTable(GDALRasterBandH, GDALColorTableH) 
> but how do we fill the
> GDALColorTableH?

Joaquim ,

The following code from gdal/alg/gdalmediancut.cpp shows adding
a bunch of entries to a color table.

     for (i = 0, ptr = usedboxes; ptr != NULL; ++i, ptr = ptr->next)
     {
         GDALColorEntry	sEntry;

         sEntry.c1 = (GByte) (((ptr->rmin + ptr->rmax) << COLOR_SHIFT) / 2);
         sEntry.c2 = (GByte) (((ptr->gmin + ptr->gmax) << COLOR_SHIFT) / 2);
         sEntry.c3 = (GByte) (((ptr->bmin + ptr->bmax) << COLOR_SHIFT) / 2);
         GDALSetColorEntry( hColorTable, i, &sEntry );
     }

Hmm, it really ought to be explicitly setting sEntry.c4 = 255 (for opaque
colors).

Best regards,
-- 
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