[gdal-dev] LibPNG compatibility issue

[Olivier BARTHELEMY]

I submitted a ticket there http://trac.osgeo.org/gdal/ticket/5204 for the
macros.

About my issue, it turns out i had not added --with-png=...., so the
compile step used the system's libpng 1.2.10. But my LD_LIBRARY_PATH must
have pointed to the directory of my libpng1.6.16, so the code compiled with
1.2 headers was linked to use 1.6.2 library , which is what i saw with ldd


2013/8/19 Even Rouault <even.rouault at mines-paris.org>

> Selon Olivier BARTHELEMY <barthelemy at geovariances.com>:
>
> > I'm having a strange error when Gdal uses libpng
> >
> > Environment :
> > x86-64 linux
> > gdal 1.10
> > libpng 1.6.2
> >
> > I am getting the following message :
> >
> > GDAL (CPLE_NotSupported): The PNG driver failed to in
> > png_create_read_struct().
> > This may be due to version compatibility problems.
> >
> > which is in this snippet in pngdataset.cpp:
> >
> > #if LIBPNG_VER_MINOR >= 2 || LIBPNG_VER_MAJOR > 1
> >         int version = png_access_version_number();
> >         CPLError( CE_Failure, CPLE_NotSupported,
> >                   "The PNG driver failed to access libpng with version
> > '%s',"
> >                   " library is actually version '%d'.\n",
> >                   PNG_LIBPNG_VER_STRING, version);
> > #else
> >         CPLError( CE_Failure, CPLE_NotSupported,
> >                   "The PNG driver failed to in
> png_create_read_struct().\n"
> >                   "This may be due to version compatibility problems." );
> > #endif
> >
> > If i understand correctly, if i get the second messsage, that is supposed
> > to mean that pngdataset.cpp was compiled with a libpng older than 1.2, or
> > that the macros don't exist (#if takes a value of 0 if a macro name is
> not
> > found)
> >
> > I compiled my GDAl with libpng 1.6.2, and ldd properly tells me that it's
> > this version GDAL tries to link to
> >
> > I think i don't get the first message because, at least for png 1.5 and
> 1.6
> > ( and even the v1.2 shipped with gdal ), LIBPNG_VER_MINOR  and
> > LIBPNG_VER_MAJOR are not in png.h. Instead, there are
> PNG_LIBPNG_VER_MINOR
> >  and PNG_LIBPNG_VER_MAJOR. So the code should also try to look for those
> > macros
>
> Yes, there's an issue in this code (could you file a ticket in GDAL Trac
> about
> that ?). But the consequence is only on the error message, not on the
> error that
> caused this code path to be reached.
>
> My assumption is that you've built a first time pngdataset.cpp against the
> GDAL
> internal libpng (1.2), and then configured later with your external libpng
> 1.6
> but pngdataset.cpp didn't get recompiled. So at runtime there's a mismatch.
>
> Try cleaning (or just "touch frmts/png/pngdataset.cpp") before rebuilding
> GDAL.
>
> >
> > As to why i am reaching this code, i couldn't find if GDAL is compatible
> > with libPNG 1.6, could you confirm it? I successfully build with it on
> > windows and linux; it works on widowns (and might have previously worked
> on
> > linux, before i recompiled gdal to add the python module)
> >
> > --
> > Olivier BARTHELEMY
> >
>
>
>


-- 
Olivier BARTHELEMY
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