Hi there,

I recently upgraded my linux distro (RH6 to RH6.2) and now
the gimp chokes on png files created by povray. It complains
about a libpng error (see subject). (Some other viewers can
see the files and some can't.)

I presume that this related to the fact that I now have libpng-1.0.5.

Anyhow, I discovered pngcrush on sourceforge that will fix the png
file so that the gimp will view it, so I have an acceptable solution
but I wondered if anyone can explain what is happening here.

Is this a bug in povray, or a problem with libpng, or something else?

Thanks for any enlightenment,

Martin
-- 
http://www.noether.freeserve.co.uk
http://www.kppp-archive.freeserve.co.uk

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Martin P Holland wrote:
> 
> Hi there,
> 
> I recently upgraded my linux distro (RH6 to RH6.2) and now
> the gimp chokes on png files created by povray. It complains
> about a libpng error (see subject). (Some other viewers can
> see the files and some can't.)
> 
> I presume that this related to the fact that I now have libpng-1.0.5.
> 
> Anyhow, I discovered pngcrush on sourceforge that will fix the png
> file so that the gimp will view it, so I have an acceptable solution
> but I wondered if anyone can explain what is happening here.
> 
> Is this a bug in povray, or a problem with libpng, or something else?
> 
> Thanks for any enlightenment,

This was discussed quit recently. Below is the answer you seek:

------------------
As seen on comp.graphics.rendering.raytracing.  Liam had been having
problems with PNG's generated by POV-Ray crashing the GIMP.  Thought
folks here might be interested.  I'm not sure how much this affects
other applications beyond the GIMP, so I'm not forwarding this to any
other groups.

Liam Devlin wrote:

> Hi,
>         I am able to create files in tga and ppm format so the problem is
> definitely with the PNG library, specifically, interaction between
> POV-Ray and the installed library. I am able to convert the generated
> ppm images to png without error. My libpng version is libpng.so.2.1.0.5.

libpng-1.0.6 (the latest, fresh from the official web site, released
just a few weeks ago) yields libpng.so.2.1.0.6.  When I compile POV-Ray
to use libpng.so.2.1.0.5 (which is what comes with Red Hat 6.2, for
instance), I produce PNG's that crash the GIMP 1.0.4 (but not various
other programs, e.g. Netscape 4.7.2, ee 0.3.11, GQview 0.7.0).  When I
downloaded and compiled libpng-1.0.6 (and zlib 1.1.3) in the POV-Ray
source directory and modified the makefile to build using those versions
(static, FWIW) rather than the ones in /usr/lib, I ended up with a
binary that produced PNG's that don't crash the GIMP.  I installed the
new libraries, recompiled POV-Ray to use the them, and those worked
fine, too.

Resolution: upgrade to the new libpng, and your problems go away. 
Currently, the problems seem to be limited to a few appliciations, but
I'll eventually want to update the version of libpng that gets
distributed with the POV-Ray source.

-Mark Gordon

-- 
Ken Tyler - 1400+ POV-Ray, Graphics, 3D Rendering, and Raytracing Links:
http://home.pacbell.net/tylereng/index.html http://www.povray.org/links/

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On Fri, 05 May 2000 13:36:33 -0700,
Ken <tyl### [at] pacbellnet> wrote:
>Martin P Holland wrote:

>> I recently upgraded my linux distro (RH6 to RH6.2) and now
>> the gimp chokes on png files created by povray. It complains
>> about a libpng error (see subject). (Some other viewers can
>> see the files and some can't.)

>This was discussed quit recently. Below is the answer you seek:

Thanks. I recompiled povray with the latest libpng and all is OK now.

atb
Martin
-- 
http://www.noether.freeserve.co.uk
http://www.kppp-archive.freeserve.co.uk

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