Re: image scaling

[David Kastrup <dak@gnu.org>]

Stefan Monnier <monnier@iro.umontreal.ca> writes:

> Looking at the Elisp manual's "38.16.2 Image Descriptors", it seems that
> we do not support image scaling.
>
> I'd like to add such a feature to image-mode.el, but am wondering how we
> should go about doing it.  Would there be some advantage to provide it
> at the C level (e.g. if some of the image libs we use already provide
> the necessary functionality) or should we just bite the bullet and call
> some external tool like "convert -scale ..." (with the disadvantage that
> flushing the image cache will not automatically cause the image to be
> re-scaled).

I think we should refactor image support somewhat: most image libraries
offer some way of loading/displaying/scaling/gamma-correcting whole
images (and where they don't, things like gdk might come in).  Yet our
code can't make use of that.  There is a reason we need an "image cache"
even though the normal image library functions would be quite fast
enough to cope with stuff on the fly.

Without refactoring the API, adding hand-spun scaling support will
further complicate future refactoring.

-- 
David Kastrup