[gdal-dev] FITS driver update?

[Even Rouault]

Bonjour Chiara,

Not being a specialist of the format, I've no in-depth opinion on the changes. 
I'm mostly surprised that the issue with the raster origin didn't surface 
before. Are there references for that ? I've CC'ed Simon Perkins (hoping his 
email is still OK) who is the original author, in case he can comment.

Regarding scaling (hoping that we talk about the same concepts), there are 2 
choices: either you apply the offset/scale automatically in IReadBlock() / 
IRasterIO() (or the underlying lib does it automatically), or you return the 
raw values and implement the GetOffset() and GetScale() method of 
GDALRasterBand (in which case, applying the scale is typically done afterwards 
with gdal_translate -unscale )

Best regards,

Even

> Hi gdal-list,
> 
> I work in a planetary/geology/astronomy lab, and I'm interested in having
> standard and full implementation of FITS format in GDAL. Geographical
> metadata are not yet well defined in FITS, then in the first time I'm just
> verifying that GDAL works as expected (by astronomers :) ) with FITS
> format.
> 
> I have forked the OsGeo project in https://github.com/epn-vespa/gdal/ and
> addressed three points: 1) FITS origin is defined on the left bottom
> corner of a raster, this is the expected behaviour of FITS processing
> software: I have modified the read and write block direction. 2) Unsigned
> INT 16 and 32 bit are supported by FITS via specific BZERO value
> (https://heasarc.gsfc.nasa.gov/docs/software/fitsio/c/c_user/node23.html):
> I have added USHORT and ULONG support. 3) BZERO BSCALE are 'reserved
> keywords' and copying them in the metadata produce inconsistency in
> reverse conversion: a FITS containing BZERO BSCALE is converted to tiff,
> tiff reconverted to FITS, BZERO BSCALE become strings and FITS
> visualization ended up in a 0 raster. I have excluded BZERO and BSCALE
> from metadata keywords.
> 
> I haven't figured out yet how to manage scaled values... this will take
> some more time, as geographical conversion.
> 
> I'm wondering if those small changes could be tested by the community and
> maybe integrated in the code at some time.
> 
> All comments are welcome!
> Thanks for listening,
> Chiara

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