Re: Image rescaling

[joakim@verona.se]

joakim@verona.se writes:

> Lars Magne Ingebrigtsen <larsi@gnus.org> writes:
>
>> Most of the image format decoders (jpeg and gif, for instance) do not
>> support image rescaling.  So shr uses ImageMagick for all its image
>> handling.
>>
>> There are two problems with this:
>>
>> 1) ImageMagick is crashy.  Virtually all Emacs crashes I get happen deep
>> in the ImageMagic code.  I mean, I don't get a lot of crashes, but they
>> happen from time to time, and are pretty annoying.
>>
>> 2) Some people run Emacs without ImageMagick built in, but usually have
>> the other libraries enabled.
>>
>> So I would propose to add a general image scaling function, and use that
>> in all the image handling functions.  Without image rescaling, Emacs is
>> pretty useless for anything that involves handling images.
>>
>> Does this sound OK to everybody?
>>
>> And if so, is there an FSF-copyright-assigned quality image rescaling
>> function out there that I could adapt to Emacs so that I don't have to
>> write it myself?  >"?
>
> Its a pity ImageMagic is crashy, but I take your word for it, since i
> dont experience it myself.
>
> Maybe something can be extracted from Gimp or Inkscape?
> Other than that, implementing a schoolbook image rescaling algorithm
> shouldnt be too much work.

OpenCV could perhaps be used as well. I have used it for mixing and
scaling of videostreams in the past, using affine transformations.

I have used GStreamer as well, but I dont know how good that is for
still image scaling.

Maybe the above libraries are too heavyweight, I'm just throwing the
ideas out there.

-- 
Joakim Verona