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Re: overlapping plots [message #1626] Mon, 10 January 1994 15:39
sterne is currently offline  sterne
Messages: 15
Registered: March 1992
Junior Member
>>>> > "Andy" == ftacn <ftacn@aurora.alaska.edu> writes:

Andy> I've got a question: I'm making some IDL plots that have shaded
Andy> regions that overlap. Right now, the region that's printed first
Andy> covers up the other region. Do you know of a way to make it so
Andy> the both shaded regions can be seen and the one in the foreground
Andy> doesn't totally block out the one behind? I guess what I want is
Andy> a shading that acts transparent so that you can still see the
Andy> shaded region under it. Did that make sense? Got any ideas?
Andy> -Andy

One way would be to get the two plots (images or whatever) into two
separate images; use tvrd to read the screen, for example, or use any of
the routines which generate an image for subsequent display by tv
(polyshade, for example).

Lets assume you end up with two equally sized byte-scaled image arrays,
front_im and back_im. Determine the value which corresponds to your
background (generally 0b on the screen, often 255b for the printer).
I'll suppose here its 0b. Then

im_final = im_front ; start to construct final image
;
ind_bg = where(im_final eq 0b) ; find indices of "background"
;
im_final(ind_bg) = im_back(ind_bg) ; overwrite background with
; back image, otherwise leaving
; front image unaffected.

tv,im_final ; display it


This can look kinda grainy unless you choose a large enough window to do
the tvrd in, but it does work.

Hope this helps,
Phil
--
------------------------------------------------------------ ---------
Philip Sterne | sterne@dublin.llnl.gov
Lawrence Livermore National Laboratory | Phone (510) 422-2510
Livermore, CA 94550 | Fax (510) 422-7300
Re: overlapping plots [message #1630 is a reply to message #1626] Mon, 10 January 1994 10:52 Go to previous message
pcp2g is currently offline  pcp2g
Messages: 3
Registered: July 1991
Junior Member
In article <1994Jan10.064703.1@aurora.alaska.edu>,
ftacn@aurora.alaska.edu writes:
|> I've got a question: I'm making
|> some IDL plots that have
|> shaded regions that overlap.
|> Right now, the region that's printed first
|> covers up the other region. Do you
|> know of a way to make it so the both
|> shaded regions can be seen and the one
|> in the foreground doesn't totally
|> block out the one behind? I guess
|> what I want is a shading that acts
|> transparent so that you can still
|> see the shaded region under it.
|> Did that make sense? Got any ideas?

If this is for a presentation, make transparent overheads
of the graphs. Then overlaying them will work.

If it's for publication, same thing: just overlay them and
xerox 'em. Not really a digital solution, but it should work.

--
* Phil Plait pcp2g@virginia.edu
* Baby Member (by 1.83 years), STOFF
* "To escape from our own island, we must each metaphorically
* kill our own Gilligan..."
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