Re: An alternative to gdk-pixbuf

[Magnus Bergman <magnus bergman snisurset net>]

On Mon, 10 Sep 2018 07:02:23 +0000
Debarshi Ray <rishi is lostca se> wrote:

> On Sun, Sep 09, 2018 at 02:57:30AM +0200, Magnus Bergman wrote:
> > Many fields of science deal with images of multi
> > gigabyte sizes. Ideally any image viewer should be able to handle
> > these too with the right plugin (probably using GEGL in that case).
> > But I think the problem with large images (say 12000x12000 or so)
> > is giving it to the application as a pixmap. From my own tests it
> > seams it's fine at least as long as the images are no bigger than
> > the screen. So if the drawing (and implicitly also scaling) is
> > handed over to the loading library (which in turn might hand it
> > over to the plugin), this problem can be avoided.  
>
> Even if one does decode the entire full resolution image into a tiled
> data structure (say, GeglBuffer), there's no need to create a Cairo
> surface for the entire image at 1:1 zoom. All that's needed is a
> surface to represent the visible area at the visible zoom. That's a
> lot more manageable.

Yes, exactly. Using abydos_render() that's very possible to implement by
the back end. Then trying to view larger images using gdk-pixbuf, I
didn't experience any particular problems then the image was at normal
size or zoomed in. The problem was zooming out. So I think just
creating one or two prescaled versions will get you quite far (as long
as there is no problem fitting the image into memory that is).