| Transparent and Overplotted Images with cgImage [message #82719] |
Sun, 13 January 2013 12:08  |
David Fanning
Messages: 11724
Registered: August 2001
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Senior Member |
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Folks,
I know some of you have been confused about transparent images and
cgImage for some time. Earlier this week, I realized I was confused,
about how things worked, too, when I wasn't able to overplot a LandSat
image onto a larger image I had. I decided to get to the bottom of it
and write an article that would explain it to all of us (but, to me
especially).
The final result (written in moments of utter despair after a shattering
loss by the Denver Broncos, the worst in Bronco history) required a
couple of changes in cgImage. You can find the latest, updated version
here:
http://www.idlcoyote.com/programs/cgimage.pro
The accompanying article, with examples, can be found here:
http://www.idlcoyote.com/cg_tips/transimage.php
My strongest motivation for creating this functionality was to be able
to locate LandSat images on top of other images so I can tell where they
are and if the data makes sense. I can now do this easily and fully
automatically if my images are stored in GeoTiff files, which mine are,
simply by setting the OVERPLOT keyword.
If you have been confused about all this and the various keywords you
can use to set transparent image properties, I think you will find the
article worth reading. I know I do. ;-)
Cheers,
David
--
David Fanning, Ph.D.
Fanning Software Consulting, Inc.
Coyote's Guide to IDL Programming: http://www.idlcoyote.com/
Sepore ma de ni thue. ("Perhaps thou speakest truth.")
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| Re: Transparent and Overplotted Images with cgImage [message #82845 is a reply to message #82719] |
Mon, 14 January 2013 19:25  |
Jeremy Bailin
Messages: 618
Registered: April 2008
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Senior Member |
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I had to laugh when I got the to AlphaBGPos keyword description... I read:
"I would say 99.9 percent of the time there is absolutly no reason to
use this keyword!"
and thought "Wait a minute, I use that!". Then I read the next line:
"I would probably remove it, except that the very first person besides
me who use the Transparent keyword with cgImage had a requirement for it."
Got to love it when you recognize yourself in Coyote programming tips... ;-)
-Jeremy.
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