Using Adaptive Zoom with irregular zoom factors (variable zoomstep?)

[Ecnassianer]

I pieced together how the adaptive zoom features work from this article
http://vservu.com/_blog/MegaZine3_-_tips,_tricks_and_hints/post/How_to_achieve_best_qualities_with_JPG_files/

And the FAQ and Hints post:
http://megazine.mightypirates.de/forum/index.php/topic,543.0.html

And did my best to roughly document it on the wiki:
http://megazine.mightypirates.de/wiki/index.php/Adaptive_Zoom

But one question remains a mystery to me. Here's my goal:

I want to make a book with 3 levels of zoom. Large (1080p), Medium (720p), and "Very Small". Large is 1.5 times as Large as Medium, and Very Small is about 1/3rd the size of medium. I don't want any of these jpegs to be scaled at all by Megazine because they contain text that I want to stay crisp, so I don't want any zoom levels other than these.

It seems that I need to set the <src>'s scale attributes to 1.5, 1.0, and .3 to match these resolutions. If I set the zoomstep to 0.5, I can get between 1.5 and 1.0, but I can't hit 0.3 in the zoom.

Is there a way to force the zoom to match src scaled attributes regardless of zoomstep?

Another way to put it: must all zoom factors be equi-distance to each other if I want their native resolutions?

[Hans Nücke]

To my knowledge actually the spacing cannot be different.
We discussed some ideas for future enhancements regarding zoom (like a zoom slider also giving feed back on the actual zoom level), and configurable zoom steps is another topic.
But no actual plans when this will be implemented...

[Ecnassianer]

Thanks for the answer hnuecke, it's good to know I should stop searching. I guess we'll just scale up the very small version to 0.5.

[Florian Nücke]

There'll be a new book attribute named "zoomsnap" in the next version, which allows setting zoom levels to which to snap to when zooming.
(say: zold = the old scale, znew = the new zoom scale; if a snap value lies in the interval ]zold, znew[, znew will be set to the snap value)
Maybe that'll help enforcing certain zoom levels. It's already in the trunk, if you want to have a look.

[Ecnassianer]

I'll throw a note on the wiki, but what will the syntax be? zstep="0.3, 1.7, 2.9"?

[Florian Nücke]

Exactly. The default is basically this:

Code: (xml)

<book zoomsnap="0.25,0.5,1,2,4,8"/>

I'll document it (and whatever else is new) in the wiki as soon as I'll get to
wrap up the next release in more detail

//Edit: gah, zoomsnap of course, not zoomstep...