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RE: trying to export pixel data from .dat files, based on coordinate loc [message #71700 is a reply to message #71616]

Mon, 12 July 2010 13:37

Snow53
Messages: 32
Registered: July 2010

Member

Thanks to all who gave great advice. I almost have this up and
running, but have a few more questions.

1. At the moment, I have tested this code based on two files that each
have their own .hdr. For the real thing, I want to create only
one .hdr that can be used for all (200+) files since they have the
same dims, data type, etc. How can I modify this code to look for that
one .hdr file and use information from that file when looping through
each file in the folder?

2. The ENVI Available Bands GUI pops up when I run this. Is this
supposed to happen? I read that envi_open_file was non-interactive in
idl (with batch mode).

3. The way the code currently reads, it will output twice when I run
it but only giving me pixel data from the first file read under
'file'. I think that I need to write a loop to specify to read from
the 'file' list one at a time, go through the code, close that file,
and then start with the next. I'm not sure, though, how to write
this, and would appreciate advice.

4. I did notice that I'm not getting back the correct sample/line
pixel file locations from my input map locations (x,y). They seem to
be one pixel off. Has anyone else had this happen?

The code is shown below. Thanks again!

Goal: Extract pixel data based on input coordinate location for each
file (ENVI binary)
; within a specified folder location. Export this data to a .csv file.

pro extractdata4

;define path
cd, 'X:\MERRA\HDF_Output_Lena\test\'

;open envi files within given folder
file_array=file_search('*.dat', count=num_file)

for i=0, num_file-1 do begin
file=file_array
endfor
print, num_file
print, file

;read ENVI binary files

envi_open_file , file, r_fid=fid

;convert x,y map coordinates to corresponding pixel coordinates. note
that xmap and ymap can be single values or arrays if
;needed to extract info for multiple pixels.
XMap=[109.55551335]
YMap=[79.25]

ENVI_CONVERT_FILE_COORDINATES, fid,XF, YF, XMap, YMap

XF_out=Round(XF)
YF_out=Round(YF)
print, 'x pix' ,XF_out
print, 'y pix', YF_out

;specify the data dims for the pixels who's info you want to extract.
pos specifies which band(s) you want to extract from.
;for example, if I have 4 bands and I only want to extract from bands
1 and 4, pos would be [0,3]. Then extract for these pixels/bands.
dims=[-1, XF_out, XF_out, YF_out, YF_out]
pos=[0]
pixdata = ENVI_GET_DATA(fid=fid, dims=dims, pos=pos)

print, pixdata
;open text file to write data to
OPENU, U, 'pixel_value.csv', /get_lun, /append
;write data
printf, U, pixdata
;close LUN
close, U

end

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[Message index]

		Re: trying to export pixel data from .dat files, based on coordinate loc By: Maxwell Peck on Fri, 09 July 2010 15:40
		Re: trying to export pixel data from .dat files, based on coordinate loc By: Maxwell Peck on Mon, 12 July 2010 14:51
		Re: trying to export pixel data from .dat files, based on coordinate loc By: Maxwell Peck on Mon, 12 July 2010 14:39
		Re: trying to export pixel data from .dat files, based on coordinate loc By: Snow53 on Mon, 12 July 2010 14:29
		Re: trying to export pixel data from .dat files, based on coordinate loc By: Maxwell Peck on Mon, 12 July 2010 14:12
		RE: trying to export pixel data from .dat files, based on coordinate loc By: Snow53 on Mon, 12 July 2010 13:37

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