[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: opening and display large file

Sylvain Carette <sylvainc@total.net> writes:

> The only other difference is that instead of extracting a subset, I used
> congrid to resample a lightweigth display grid. Even though, nothing on tv
> and a small portion with slide_image which disapear immediately as soon I
> move a scroll bar (retain=0; retain 1 & 2 just make windows crash)...
> So this mean that 4800 x 6000 is too big for those two function? I still
> dont understand why it would be so big since according to the doc, you
> should be able to open a file as long you have enough memory and I have
> 250mb which should be enough for one gtopo tile no?

An image of 4800 x 6000 is getting pretty big.  A test on my machine
(Solaris) has brought it to its knees.  At the rendering stage with
SLIDE_IMAGE, it hung for a few minutes.  I believe this is because the
entire image must be loaded into the window manager memory.  However
IDL itself was able manipulate the arrays pretty easily (RAM=256mb).

The difference between taking a subset and using CONGRID could be
large.  However I had no problem using it to downsample a 4800x6000
array.  That's strange.

If you can't get away with looking at small tiles, then you may be
able to modify SLIDE_IMAGE.  You'll have to study up on widgets, find
out about VIEWPORT_EVENTS, and then make an event handler that
re-renders the exposed portions when you scroll.  Either that or make
a simple widget with directional buttons like mapquest.com, and render
your tiles like that.

 > Give me an open file to work with, and I know what to do after. I sell my
 > piano to buy IDL naively thinking that it was handling large file ( well,
 > RSI claim they have "industrial strenght" tool to handle very large stuff ).
 > Where are those functionality?
 > Do I need to write my own image manager? Should I have buy ErMapper instead?

Your demands place you in the 0.1% group.  The other 99.9% people
don't need the features.  IDL itself is pretty general purpose.  I
believe that ENVI is designed to do exactly what you want.

If you want industrial strength professional tools to work on
industrial sized images doing industrial tasks, and you *aren't*
willing to pay industrial prices, well what can I say?


Craig B. Markwardt, Ph.D.         EMAIL:    craigmnet@cow.physics.wisc.edu
Astrophysics, IDL, Finance, Derivatives | Remove "net" for better response