| Re: performing a TVRD() on 24 bit images... [message #9806 is a reply to message #9736] |
Wed, 20 August 1997 00:00   |
tdarnell
Messages: 3
Registered: August 1997
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Junior Member |
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In article <grunes.596.871738018@imsy1.nrl.navy.mil>,
grunes@imsy1.nrl.navy.mil (Mitchell R Grunes) writes:
>
> There are a number of potential problems with xv
> (and other display programs) that could be causing
> your problem. E.G., if the image is larger than
> the xv display window, xv would sub-sample it,
> producing interesting side effects. Other side
> effects can result from a image that is smaller
> than the xv display window, resulting from
> uneven pixel replication.
Thanks, I considered that so I viewed the image in a variety of viewers
on different platforms, all were the same.
>
> I use IDL or WAVE for display because I know that I
> can control exactly what they do, if I work at it,
Yeah, but I've noticed that sometimes we have to really work at it :-)
>
> I'm sure David Fanning's method of dealing with 8 bit
> images works, but if you really want to read 24 bit color
His method did work better than using tvrd(true=1), there was no loss
of contrast. The problem now is how do I place a smaller array in the
middle of a larger one without destroying the information underneath the
smaller array. (These are composite images of two datasets).
The nice thing about loading a colortable, tv'ing the image to a pixmap,
loading a second colortable, and tv'ing the second image to the pixmap,
was that I got exactly the effect I wanted: two images, each with its
own colortable superimposed on each other. I was able to see red solar
prominences 'underneath' a blue coronal image. This allowed us to see
how an event (say a coronal mass ejection) appeared in two datasets at
the same time. All that was left to do was get the info in the window into
a file (sigh). Unfortunately, tvrd() didn't give me what was
on the window. (No WYSIWYG here!)
I've been working with a tech support guy at RSI and he seems to think it is
in the TVRD() procedure (I'm inclined to agree). I've noticed before on an
unrelated problem that IDL does its own thing (at least on a SUN) with the
display and colors. This was certainly true when it came to GAMMA settings
on the monitor. In order for true color images to look consistent with our
SGI's and even in xv on the same system, our system admin had to change the
gamma to its 'linear' setting (apparently only root can do this). After that
change, what we saw in IDL was the same as what we saw in other imagers like
xv.
Thanks for your reply and suggestion, unfortunately, I've already tried most
of what you suggested. Just to be sure, I used REVERSE in the TIFF_WRITE
call to see if that mattered. It didn't. I wish I could help you with your
job hunt, but alas I am only a lowly IDL programmer. I know nothing about
what positions are available. Good luck in your search!
--
Tony Darnell
High Altitude Observatory
(tdarnell@hao.ucar.edu) Boulder, CO
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