| Re: Setting data coordinates [message #35921] |
Tue, 29 July 2003 16:46  |
David Fanning
Messages: 11724
Registered: August 2001
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Senior Member |
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Marshall Perrin writes:
> Wow, my brain clearly slipped a cog there. I *meant* to write
> "direct graphics" after all.
Ah, right. :-)
Well, in the Catalyst Object Library Dave and I continue
to work on (without making any progress toward completion,
apparently) a data object always contains "pockets" (I
guess you could call them) for holding a coordinate
object and a color object. Before the data "draws itself"
in direct graphics, it "draws" its color object to set
up the proper drawing colors and it "draws" its coordinate
object to set up the proper coordinate system.
Draw widgets in our system know this about objects they
draw, of course, so they can always say to the data object
"given this point in the draw widget, tell me what the
corresponding point is in the coordinate system associated
with you". In this way, you can associate a map coordinate
object with an image object and always immediately find
out the lat/lon location of a click inside the image (or
anywhere else in the window).
Similarly, once a data object sets up a coordinate system,
any secondary object contained in the object's container
can be drawn in the same coordinate system. It gives a
sort of object graphics kind of feel to direct graphics
objects, without having to get terribly bogged down in
learning a completely new graphics system. Something to
keep in mind as IDL 6.0 comes out. :-)
Cheers,
David
--
David W. Fanning, Ph.D.
Fanning Software Consulting, Inc.
Phone: 970-221-0438, E-mail: david@dfanning.com
Coyote's Guide to IDL Programming: http://www.dfanning.com/
Toll-Free IDL Book Orders: 1-888-461-0155
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