Re: fast image paging

[Stefan Monnier <monnier@IRO.UMontreal.CA>]

> Greetings!  I have a djvu mode which is designed for scholars reading,
> annotating, and cross-referencing many large documents.  Right now I use
> pbm formats and create-image.  This makes it easy to highlight and
> correlate pixels with text, but the images can get quite large, making
> handling sluggish on slower machines.  

> Will I improve anything here using a compressed format like png?  Or,
> when emacs displays and moves the image, does it decompress the image
> anyway into the same sized internal data structure?

I don't know the precise details, but I think that if you use PNG you
won't gain much because indeed, the png library will begin by
decompressing the image and keeping it that way in memory.

You might have better luck if you use the `imagemagick' image type,
which might be able to render dejavu directly (i.e. without going
through pbm/png/...), so only the current page is kept in decompressed
bitmap form.

IIRC last time someone tried to use it there were some problems
(performance, maybe?).  Those problems may have been fixed since,
I can't remember.  It's definitely worth a try, I think, tho.

And I'd be very happy to see your mode in GNU ELPA, so if you're
interested in submitting it for inclusion, send me an email,


        Stefan