| Image and Maps with IDL8 [message #72620] |
Wed, 22 September 2010 11:43 |
David Fanning
Messages: 11724
Registered: August 2001
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Senior Member |
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Folks,
Well, I have spent another fruitless morning trying to
figure out how to display a gridded, map projected image
with map annotations (continents and grids) on it in
the new IDL8 graphics. I have gotten, sad to say, just
about nowhere. :-(
Here is what I am trying to do:
http://www.dfanning.com/catalyst/maponimage.html
I guess any question at all would be as good as any.
How do I know where the image function located the
image in the window? I need to know this so I could
position the map function. (I mean, hypothetically.)
The on-line help says the image function has a property
image_location. But when I try to access that, the image
function glares at me:
IDL> img = image(image)
IDL> print, img.image_location
% PRINT: Variable is undefined: <UNDEFINED>.
There is a "location", but that doesn't tell me what
I want to know. "Position" works (or doesn't, in this
case) like image_location.
The real problem appears to be that the map function
seems to work in lat/lon space. But, when professionals
do map projections, they *always* work in XY space. My
*image* is in XY space. That's the only space with a
regular grid! Help! I need a map function that knows
how to set up an XY data space or mapping is generally
hopeless, it seems to me. :-(
I do note that the map function has XRANGE and YRANGE
keywords, but when filled with the proper XY values,
they appear to be completely ignored by the map function.
(The documentation doesn't indicate what units the ranges
are suppose to be given in.)
Any and all help welcome.
Cheers,
David
P.S. I did get one bit of good news this morning. The
programmer who wrote CTLOAD was on the ball and had
already anticipated the new IDL graphics and their lack
of support for Brewer color tables. :-)
If you want to use Brewer colors, you can try this:
IDL> CTLoad, 4, /Brewer, RGB_TABLE=rgb
IDL> img = Image(my_2d_image, RGB_TABLE=rgb)
Of course, you will need other things, but you probably
already have those, too. :-)
http://www.dfanning.com/color_tips/brewer.html
--
David Fanning, Ph.D.
Fanning Software Consulting, Inc.
Coyote's Guide to IDL Programming: http://www.dfanning.com/
Sepore ma de ni thui. ("Perhaps thou speakest truth.")
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