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Re: imagemagic in image-mode and image-dired-thumbnail-mode?


From: Stephen J. Turnbull
Subject: Re: imagemagic in image-mode and image-dired-thumbnail-mode?
Date: Mon, 15 Jul 2013 14:45:26 +0900

Eli Zaretskii writes:

 > > Eli, are you proposing to do the work yourself?
 > 
 > You know very well that if I did, I would not be speaking here, but
 > instead coding and committing.

Really?  Given several people who are interested in this feature
although unable to do significant work on it at the moment?  I didn't
realize you were an advocate of "last commit wins". ;-)

 > I don't disagree with the principle, but the results are evidently not
 > very satisfactory.

Image libraries suck, that's part of life.  How many PNG crashes and
GIF crashes have been fixed upstream?  How many of these libraries
have undocumented restrictions on arguments or image formats that
people have had to guess at over the years?  How many more of those
undocumented restrictions will have to be deduced in order to add
features like scaling, one at a time?  I don't know the details, but I
can tell you that over the last ten years, as far as those affecting
XEmacs go, the answers are "lots", "all of them", and "dunno, but past
experience doesn't allow me to be optimistic".

One advantage to using a higher level API such as ImageMagick's is
that somebody else takes care of that.  Assuming they do it well, of
course.  The PDF crash is one strike against ImageMagick, of course,
but PDF is hard.  So hard that Adobe wontfixes crashers in Acrobat
they themselves confirm (of course, only in cases where Adobe software
happens not to produce the dangerous expressions).  One was so bad it
sometimes blue-screened NT.

 > > XEmacs did try the same strategy with ImageMagick and abandoned it
 > > (too unstable, too many undocumented crashers) -- but that was over
 > > ten years ago.  Surely ImageMagick has improved over the years.
 > 
 > Evidently, the improvement is not enough, see the rest of this
 > thread.

AFAICS, there are serious bugs in PDF handling.  Screw you very much,
Adobe.  What else can we say about that?  If Emacs wants to use a
different library "just for PDF", that sounds reasonable to me.  But
that's an issue with PDF in general, not really one with ImageMagick.
AFAIK, no matter what PDF library you use[1], Adobe's next release is
a loaded gun at your head.

With respect to the other issues that remain, as I wrote before, I
suspect that they are mostly cases where somebody in a hurry to commit
something cool didn't bother with the full ImageMagick API and left
other cool features unimplemented.  That's life in a project with no
formal review process.

 > You didn't mention scaling, which seems to be the trigger for this
 > thread.

Other people mentioned it, so I didn't think I needed to. :-)

Footnotes: 
[1]  Among the more-or-less standalone libraries.  I imagine the ones
used by KDE and GNOME are pretty stable but bring in huge dependencies.




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