[gdal-dev] FITS driver update?

[Simon Perkins]

There might be other private users of the FITS driver that wouldn't show up
in a search, but likely there aren't many.

How about if you at least have something like a compile-time define that
sets the FITS y-flip behavior? That would at least give people a way of
getting the old behavior if they want it, if they bring in fresh GDAL and
recompile? The default could be your new behavior.

Feel free to work with Even to incorporate your changes into the FITS
driver. I don't have time to help with this myself...

Cheers!

On Fri, Mar 25, 2016 at 3:41 PM Chiara Marmo <chiara.marmo at u-psud.fr> wrote:

> Hi Simon,
>
> > It's been well over a decade since I last looked at this code, and I
> > originally wrote it for a non-astronomy use-case (we just needed a format
> > that could handle multi-spectral imagery), so it's entirely possible it
> > doesn't quite align with normal astronomy conventions... My main concern
> > though is that making these changes would likely break existing code that
> > uses this library. Maybe you could add a param to enable a "flip" mode
> that
> > flips the y-axis while keeping the current default behavior?
>
> I did a (quick, maybe incomplete) research on which software uses gdal to
> read FITS and the only one I have found, beeing largely used , is QGIS. I
> do not know a lot of peaple (excepting me :) ) using QGIS to display
> FITS... that's why I'm working on that.
>
> > - I tend to think of image origin as a display issue. It's not clear to
> me
> > that GDAL implies any particular origin for its coordinate system, so it
> > seems simpler to me to have the first row of data in the FITS file
> > correspond to the first row of data from GDAL's POV as well. For that
> > matter, it's not clear to me that FITS implies a specific origin -
> > displaying the first pixel in the lower left is more of a convention?
> It's
> > true that converting to a TIFF and then displaying the TIFF in the usual
> way
> > flips the image, but I'd probably tackle that by simply flipping the TIFF
> > image vertically after conversion rather than messing around with the
> data
> > ordering. Just my 2c.
>
> Indeed, the standard description of FITS says that for raster the origin
> is bottom left pixel, and its center is 1,1: those two definitions are
> important when georeferencing a raster.
> I'm working at the inteface between planetary mappers , using GIS software
> and GDAL, and astronomers ,using traditional FITS visualization software
> (like Aladin or ds9): FITS images are sometimes raw data, without
> geographical information, the results is that GDAL based tools display
> flipped FITS with respect to astronomical software. Each time I have to
> explain that there is a different convention in FITS and generic raster
> description in computer sciences and direction doesn't matter... but users
> do forget fast...
>
> I need homogeneity in visualization for the two communities could talk
> together... :)
>
> > - Implementing the BSCALE and BZERO via GetOffset() and GetScale() sounds
> > like a good idea, in which case, it's fine to exclude those keywords from
> > the metadata.
>
> Yep, thanks Even for suggestion.
>
> Chiara
>
> --
> Chiara Marmo
> Ingénieur de Recherche GEOPS - Paris Sud-11
> Bât 509
> Tel: +33 (0)1 69 15 49 03
>
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