Re: image scaling

[Chong Yidong <cyd@stupidchicken.com>]

"Juanma Barranquero" <lekktu@gmail.com> writes:

>>  Maybe the scaling is part of a series of operations,
>>  the end of which would be displayable but not the middle.
>
> I'm not sure I understand. A series of operations (presumably, image
> transformations of some sort) without the image library support? We do
> that today, manipulating for example PNG images without (statically or
> dynamically) linking libpng?

Suppose, for example, we "outsource" image transformations to a
specific external library.  For the sake of argument, let's say this
library is libpng.

One way to do this is to have Emacs use libpng internally to store and
manipulate (e.g. rescale) images, instead of the pixel buffer system
we currently use.  Alternatively, Emacs might keep the pixel buffer
system, but perform image manipulations by converting the image into a
png internally, calling the relevant libpng function to rescale it or
whatever, and then converting it back.

We would thus be using libpng to perform image manipulations, for
arbitrary images and not just pngs.  The trouble is that if libpng is
not available, all this functionality would disappear (not just for
pngs, but also for gifs or whatever other images *are* supported).  In
that case, how would we handle this at the Lisp interface level?