Re: [wxperl-users] Handling a large zoomable image (world map)

[Donovan A. <al...@Zo...>]

The method described below is the direction I would take, but treating =
it more like a tiled 2d game.
=20
In more modern (heh) 2d tile map games, there is a "viewport rectangle" =
and a "worldview rectangle".  You draw only the viewport rectangle's =
tiles, but you store an extra amount of neighboring tiles (the size of =
which is more like a worldview).  As the viewport is moved, free the =
tiles that are now outside of the worldview rectangle and load (in a =
thread perhaps?) the new (non-visible) "worldview rectangles".
=20
This provides efficient memory use & smoother loading at the cost of =
greater complexity & having to break your source image into tiles (which =
you do once and save the tiles and a map of coords to the specific =
tiles).
=20
Anyway, just some more food for thought.  If you go this route, there is =
plenty of reading out there on this topic for 2d games.

=20
________________________________

From: wxp...@li... on behalf of Jouke =
Visser
Sent: Tue 6/27/2006 6:37 AM
To: Ed W
Cc: wxp...@li...
Subject: Re: [wxperl-users] Handling a large zoomable image (world map)



Hi Ed,

> Oooh.  I say!  Now that looks really nice for all kinds of reasons!
> Thanks for creating this
My pleasure. If you encounter any bugs, let me know via CPAN's RT.

> What's likely the best technique to handle an oversized image with a
> small viewport in Image:Magick?  I'm guessing that I will have to use =
a
> static image and some slider bars to emulate the effect of a viewport =
on
> a much larger sub image?  Are there any other useful features in
> Image::Magick which can help support the viewport kind of model?
Well, you could take the original image, and crop (see the crop method
in Image::Magick's documentation) pieces of it and put that in your
window. When the user wants to scroll a whole page in any direction
(north, east, south or west), you could crop again from the original,
and if someone would just want to move in any direction for only a few
pixels, maybe it's faster to crop that extra bit and add it to the copy
you're already displaying. You can easily "montage" (see IM docs again)
several pieces together...

Since Wx::Perl::Imagick gives you more image manipulation possibilities,
you could also choose to put a kind of compass on top of your image and
let the user use that for navigation, or whatever you'd want.

I usually get the best ideas for solving my Image manipulation issues by
browsing through Image::Magick's documentation (a link to that can be
found in the Wx::Perl::Imagick POD), and read what the various methods =
do.

HTH,

Jouke

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