[gdal-dev] GeoTiff and the 4th band

[Nicolas Mayer]

Even, thank you very much for answering me so quicly

With the PHOTOMETRIC creation option to MINISBLACK, I get now :
Band 1 Block=100x20 Type=Byte, ColorInterp=Gray
Band 2 Block=100x20 Type=Byte, ColorInterp=Undefined
Band 3 Block=100x20 Type=Byte, ColorInterp=Undefined
Band 4 Block=100x20 Type=Byte, ColorInterp=Undefined

Does this option change anything in the metadatas or in the headers of the
written file ?

But I try to make the same thing as an exemple file I have, which has this
interpretation whith gdalinfo (GDAL 1.7.3) :

Metadata:
  TIFFTAG_IMAGEDESCRIPTION=B3 B2 B1 B4
  TIFFTAG_DATETIME=20050824 18:08:22
  AREA_OR_POINT=Point
Image Structure Metadata:
  INTERLEAVE=BAND
Corner Coordinates:
Upper Left  (    0.0,    0.0)
Lower Left  (    0.0, 3000.0)
Upper Right ( 3000.0,    0.0)
Lower Right ( 3000.0, 3000.0)
Center      ( 1500.0, 1500.0)
Band 1 Block=3000x500 Type=Byte, ColorInterp=Red
Band 2 Block=3000x500 Type=Byte, ColorInterp=Green
Band 3 Block=3000x500 Type=Byte, ColorInterp=Blue
Band 4 Block=3000x500 Type=Byte, ColorInterp=Undefined

My goal is to have an "RGB-Undefined" color interpretation.
Have you any idea of the creation option (or driver option ?) to set to have
the same color interpretations ?

Thank you in advance

Nicky



2011/4/18 Even Rouault <even.rouault at mines-paris.org>

> Selon Nicolas Mayer <nmayer31000 at gmail.com>:
>
> Retry by setting the PHOTOMETRIC creation option to MINISBLACK. Otherwise,
> by
> default, without specifying it, GDAL assumes that the PHOTOMETRIC is RGB
> and
> that the 4th band is an alpha band.
>
> You should get :
> Band 1 Block=100x20 Type=Byte, ColorInterp=Gray
> Band 2 Block=100x20 Type=Byte, ColorInterp=Undefined
> Band 3 Block=100x20 Type=Byte, ColorInterp=Undefined
> Band 4 Block=100x20 Type=Byte, ColorInterp=Undefined
>
> There's no way in the TIFF format to really specify the color
> interpretation of
> each band. The way GDAL builds the color interpretation when reading a TIFF
> file
> is a combination of the value of the PHOTOMETRIC and EXTRASAMPLES tag.
>
> > Hello
> >
> > I have a problem with the geotiff (GTiff) driver.
> >
> > I create a 4-bands raster image in a c++ program. The fourth band was
> > considered as an alpha band in the geotiff image (actually, it is near
> > infrared : NIR)
> >
> > $ gdalinfo new_geotiff.tif
> > Driver: GTiff/GeoTIFF
> > Files: new__geotiff.tif
> > Size is 100, 100
> > (...)
> > Band 1 Block=100x20 Type=Byte, ColorInterp=Red
> >   Mask Flags: PER_DATASET ALPHA
> > Band 2 Block=100x20 Type=Byte, ColorInterp=Green
> >   Mask Flags: PER_DATASET ALPHA
> > Band 3 Block=100x20 Type=Byte, ColorInterp=Blue
> >   Mask Flags: PER_DATASET ALPHA
> > Band 4 Block=100x20 Type=Byte, ColorInterp=Alpha
> >
> > How to remove the Color interpretation 'alpha' and the mask flags ?
> >
> > I want to have :
> >
> > Band 1 Block=100x20 Type=Byte, ColorInterp=Red
> > Band 2 Block=100x20 Type=Byte, ColorInterp=Green
> > Band 3 Block=100x20 Type=Byte, ColorInterp=Blue
> > Band 4 Block=100x20 Type=Byte, ColorInterp=Undefined
> >
> > I already tryed :
> > pDS->GetRasterBand(4)->SetColorInterpretation(GCI_Undefined );
> >
> > I tryed too to set the creation option : "ALPHA" to "NO".
> >
> >
> > Thanks in advance for any help.
> >
> > Nicky
> >
>
>
>
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