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Re: [udig-devel] Consistant GIS image files w/ geo-referencing
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backspaces wrote:
So question number one is: Is there a way for me to export and image of a
GIS area in uDig and get a consistent image of it (same pixel size/area,
same uDig GIS content (i.e. same exact scale and same position, upper left
corner or some similar reference)? The screen-grab approach seems pretty
extream! :)
A perfectly reasonable request: Check out the community section; Jesse
has a PNG and PDF export example working over there.
You should be able to modify the code to export a consistent image each
time; if needed you can place a rectangle
on the map blackboard and export that region each time. You may need to
create your own tool to define that rectangle (or perhaps a dialog
to enter in the bounds?).
By now you must be thinking we're pretty weird, but wait .. there's more!
After we do a run of the ABM, we import it into Blender, a 3D modeling
system, so that we can get much more visually compelling movies. So this
means the image above must not only be consistent in terms pixel placement
and area and so on, it must be geo-registered in some way. As I understand
it, there is the notion of a "world file" in GIS which is a registration
file accompanying an image saying what the geo-coordinate of the upper left
corner is, and what the pixel size is in world coordinates (i.e. how many
meters on a side a pixel is).
Right right; what you describe is the next step for that PNG tool. You
can have a look at the example data from the uDig tutorial
(it includes some of those world files you need). I think the world file
is simply the bounds; an "prj" file describe the projection
the bounds (and hense the image) are in. To figure out the size of a
pixel from this information you would need to do some math.
I've tried making a layer of two markers that would be the desired extent,
using the uDig zoom-to-layer feature, and entering the scale as a consistent
value, but this does not appear to work. I get inconsistent zooms and
entering a scale changes whenever I enter it to a similar scale but not the
same scale. I realize its asking uDig a lot to be pixel-perfect!
Whew! So is there a way for me to achieve this sort of repeatable export of
a map area with a given pixel height and width, and with the geo-coordinate
information so that it can be imported into other programs in a standard
way?? How would you try to do this?
Are you a programmer? If not can we ask you to hire one for a couple
days work :-)
I bet this is the weirdest use of uDig yet!
Owen
Sounds like a great deal of fun,
Jody
