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Re: envi_get_data [message #68168 is a reply to message #58173]

Wed, 30 September 2009 02:39

wita
Messages: 43
Registered: January 2005

Member

woods1 wrote:
> Hi,
> i have a problem.
> i try this: img = envi_get_data(fid=De_fid, dims=dims,pos=pos), but i

Hi,

Using ENVI_Get_Data() on such large images is really a bad idea.
Trying to read the whole image will take more then 2Gb of memory (in
case of 8bit data) and you will have trouble to fit it in memory on
any 32 bit operating system.

What you should do instead is use ENVI's tiling mechanism to read your
image in chunks and loop over the number of tiles. Then resample each
tile to be able to display it (or do whatever processing you want) and
stitch the results together. So in pseudo code it should look like
this:

tile_ID = ENVI_Init_Tile(File_ID, NUM_TILES=num_tiles,
INTERLEAVE=1, ....)
FOR i=0L, num_tiles-1 DO BEGIN
data = ENVI_Get_Tile(tile_ID)
<processing data goes here>
ENDFOR
ENVI_Tile_Done, tile_ID

Setting INTERLEAVE=1 ensures that you read your file line by line. It
may be more efficient to use INTERLEAVE=0 but then you need to write
some logic that handles the size of the tile that ENVI_Get_Tile
returns, which depends on you memory settings.

Hope this helps.

Allard

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[Message index]

		envi_get_data By: yychongzi on Mon, 21 January 2008 11:42
		Re: envi_get_data By: lbusett@yahoo.it on Fri, 25 January 2008 06:03
		Re: envi_get_data By: peter.eddy@shaw.ca on Fri, 25 January 2008 09:18
		Re: envi_get_data By: Jean H. on Fri, 25 January 2008 13:49
		Re: envi_get_data By: yychongzi on Fri, 25 January 2008 13:25
		Re: envi_get_data By: woods1 on Tue, 15 September 2009 00:12
		Re: envi_get_data By: Robert Moss, PhD on Mon, 14 September 2009 11:59
		Re: envi_get_data By: Andrew Rodger on Fri, 02 October 2009 06:29
		Re: envi_get_data By: woods1 on Thu, 01 October 2009 09:48
		Re: envi_get_data By: David Fanning on Wed, 30 September 2009 07:34
		Re: envi_get_data By: woods1 on Wed, 30 September 2009 07:14
		Re: envi_get_data By: wita on Wed, 30 September 2009 02:39
		Re: envi_get_data By: woods1 on Wed, 30 September 2009 01:25
		Re: envi_get_data By: woods1 on Wed, 30 September 2009 01:09
		Re: envi_get_data By: woods1 on Wed, 30 September 2009 01:02
		Re: envi_get_data By: Chris Jengo on Tue, 29 September 2009 07:40
		Re: envi_get_data By: David Fanning on Tue, 29 September 2009 06:18
		Re: envi_get_data By: lefsky@gmail.com on Mon, 12 November 2012 14:02
		Re: envi_get_data By: lefsky@gmail.com on Sun, 11 November 2012 20:22

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