| Re: Overlaying vector files on multiple HDF files in IDL [message #57783] |
Sun, 30 December 2007 06:51 |
David Fanning
Messages: 11724
Registered: August 2001
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Senior Member |
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vinpan writes:
> I am new to IDL programming, not sure if this question is relevant
> here.
> I have more than 100 hdf file of same dimention/area and I have a
> vector file (.evf) that I need to overlay on each hdf file and subset
> them to new set of images. I need to write IDL program for this.
>
>
> I could do this in ENVI 'for one image' with following steps,
> 1. open hdf file and load band.
> 2. overlay vectors.. open vector file.. double click on first table
> item.
> 3.export active layer t ROI. + convert all records of an EVI to one
> ROI.
> 4.finally, Basic tools -> subset via RIOs.
>
> But could not understand how to carryout these steps in IDL
>
> Could anybody guide me?
It's hard to know what you are asking for here. I guess
you are aware that IDL is a programming language, and you
might have to learn a LOT of things to write something like
this IDL. (The reason you pay the big bucks for ENVI is
that you are paying someone else to learn all these things
for you.) It is sort of like asking us how to add an addition
on to your house, complete with plumbing and electrical
instructions. It's not something we could normally do in
a couple of paragraphs.
Maybe you just want an outline of what you need to know.
Here is how I would proceed with this.
1. Open and read the vector file. Since ENVI already does
this, you may be able to take advantage of an ENVI routine to
do the reading for you. That will be a big help. Sort of like
having a brother-in-law who is a plumber.
2. Put the vectors into an IDLanROI object. This will allow
you to create an image mask.
3. In a loop, open your HDF files and extract your image
(brother-in-law will come in handy here, too). Multiply
the image by the image mask created in Step 2. Resize
or subset the image, as required.
That's it. Pretty simple in theory. :-)
Cheers,
David
--
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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