[conspire] [Gimp-user] PNG troubles

[Rick Moen]

Quoting Ruben Safir (ruben at mrbrklyn.com):

> > Your claim that PNG is wholly undependable and not a usable format is
> > _also_ grossly inaccurate.  
> 
> Its not a claim but a hypothesis based on experience.  twice in 20 years
> I found problems with previously made PNG files that later failed to be
> renderable by the (at the time) current PNG.

It was a non-sequitur the first time you said it, and it remains one
upon further repetition.

I see no reason to dispute the matter with you further, as I think the
point is pretty obvious:  The PNG specification doesn't say how zlib
compression should work[1], much less is it the fault of the specification
that a zlib implementation leveraged by a long-ago release of libpng
calculated incorrect zlib checksums, and a later implementation enforced
valid zlib checksums.

All of the effort you're spending generating online gratuitous drama
would be better spent compiling and using PNG utilities to correct your 
slightly defective old images.

> They seem to have a small application which fixes the files I showed
> them, so that is good.

Great.  Use it.  Lose the drama.


If you decide you don't like PNG, you're free to convert your files over
to GIF and use that.  Happy ending.


[1] As you probably know, that spec is defined in RFC-1950.  The PNG
spec does constrain what -subtype- of zlib compression may be used.
http://www.libpng.org/pub/png/spec/1.2/PNG-Compression.html