| Re: trying to export pixel data from .dat files, based on coordinate loc [message #71698 is a reply to message #71616] |
Mon, 12 July 2010 14:29   |
Snow53
Messages: 32
Registered: July 2010
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Member |
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On Jul 12, 3:12 pm, Maxwell Peck <maxjp...@gmail.com> wrote:
> On Jul 13, 6:37 am, Snow53 <jennifer_wa...@hotmail.com> wrote:
>
>
>
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>> 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
>
> 1. It can be done just using IDL to read in the images but it will
> probably be easier for you just to duplicate the header file and keep
> them in ENVI format. (Unless you wanted to completely rewrite the
> program)
>
> 2. You probably want ,/NO_REALISE in your envi_open_file.
>
> 3. Yes, use ENVI_FILE_MNG to close the file each time after the map
> conversion.
>
> 4. Is it one pixel off or half a pixel off ?
>
> Max- Hide quoted text -
>
> - Show quoted text -
Thanks Max.
I just checked and it is one pixel off, not 0.5.
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