| Re: opening and display large file [message #21557 is a reply to message #21548] |
Wed, 30 August 2000 00:00   |
Sylvain Carette
Messages: 19
Registered: May 2000
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Junior Member |
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<tt>Thanks</tt>
<br><tt>That's look almost what I have tryed. I'll use it "as is" to see
the difference with mine but its mostly the fact I tryed to send the whole
array to tv and slide_image.</tt>
<br><tt>Also, I didnt close the file and free lun immediately after reading
as you did - is this could cause memory leakage (when freezing, I was wondering
after reset if I left big lump of anaccessible memory)?</tt>
<br><tt>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)...</tt>
<br><tt>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?</tt><tt></tt>
<p><tt>I hope I dont sound like a bugger but beleive me, I tryed to do
my homework before requesting help here.</tt>
<br><tt>BYW, did you open usgs dem?</tt><tt></tt>
<p><tt>Sylvain Carette</tt>
<br><tt>VRML designer-composer</tt><tt></tt>
<p><tt>Kelly Dean wrote:</tt>
<blockquote TYPE=CITE><tt>This is what I use to access the GTOPO30 DEMs</tt><tt></tt>
<p><tt> Kelly Dean</tt>
<br><tt> CSU/CIRA</tt><tt></tt>
<p><tt>================================================</tt >
<br><tt>PRO ReadTopo</tt><tt></tt>
<p><tt>file = 'e:\w140n90\w140n90.dem</tt>
<br><tt>topo = INTarr(4800,6000)</tt>
<br><tt>;</tt>
<br><tt>; Open DEM, Swap_Endian if you are using a PC.</tt>
<br><tt>;</tt>
<br><tt>OpenR, lun, file, /Get_Lun, /swap_endian</tt>
<br><tt>ReadU, lun, topo</tt>
<br><tt>Close, lun</tt>
<br><tt>Free_Lun, lun</tt>
<br><tt>;</tt>
<br><tt>; Cut out a small area and scale it.</tt>
<br><tt>;</tt>
<br><tt>cut = BYTscl(topo(1500:2499,1500:2499), MIN=0 )</tt>
<br><tt>PRINT, ' MAX >',MAX( cut , MIN=MIN)</tt>
<br><tt>PRINT, ' MIN >',MIN</tt>
<br><tt>WINDOW, 0, XSize=1000, YSize=1000, TITLE='GTOP030'</tt>
<br><tt>TV, cut</tt><tt></tt>
<p><tt>END</tt>
<br><tt>=================================================</tt ><tt></tt>
<p><tt>Sylvain Carette wrote:</tt><tt></tt>
<p><tt>> Hi</tt>
<br><tt>> How do you manage to display very large images? What is the options?</tt>
<br><tt>> From the manual, it seem that using "assoc" is a winner but maybe
with</tt>
<br><tt>> one little example it would be more clear how can this be (It
seem to</tt>
<br><tt>> me that it is an important aspect of programming with IDL since
most</tt>
<br><tt>> of the time you'll deal with larger than memory files).</tt>
<br><tt>> Even with assoc, dont you still have to copy from the file to
an array</tt>
<br><tt>> before display?</tt>
<br><tt>> I dont decipher exactly why and when to use readu or read_binary,
the</tt>
<br><tt>> file pointer, assoc or writing to an offscreen buffer.</tt>
<br><tt>></tt>
<br><tt>> I tried to open and display a GTOPO30 tile (4800 x 6000 int).
tv could</tt>
<br><tt>> not display it - froze. I tried "slide_image" but it didnt scroll
with</tt>
<br><tt>> "retain=1" while "retain=2" and "retain=3" result in windows
error and</tt>
<br><tt>> crash.</tt>
<br><tt>></tt>
<br><tt>> Since most of my data fall in the 30mb to 610 mb range, I need</tt>
<br><tt>> absolutely to open and display very large file. What is available?</tt>
<br><tt>> Pointers, sample code, library, ideas, etc, I'm listening....
Just</tt>
<br><tt>> knowing that it have to be handled on your own or that IDL provide</tt>
<br><tt>> facility (that they forgot to explain in the manual) to deal
with this</tt>
<br><tt>> will already be invaluable</tt>
<br><tt>></tt>
<br><tt>> Thanks</tt>
<br><tt>></tt>
<br><tt>> Sylvain Carette</tt>
<br><tt>> VRML designer-composer</tt>
<br><tt>></tt></blockquote>
<tt></tt></html>
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