Dear all,

I've been trying to calculate deviation of each image from the mean at
pixel by pixel basis.
When I checked pixel values, they look to be way high.
I've trying to figure it out, but due to my short knowledge of IDL,
problem solving doesn't seem to progress.
For your better understanding, I would like to show what I wrote.
I really appreciate for your comments and advice.

;-------------------------------------------------------------------------------------------------
pro deviation

file = File_Search('C:\DataProcessing\Images\*.tif', Count=count)

nImages = n_elements(file)

  OK = QUERY_TIFF(file[0], info)
  print, info.dimensions

  imageSize = info.dimensions
  ns = imageSize[0]
  nl = imageSize[1]

Volume = fltarr(ns, nl, nImages)
imageMean = fltarr(ns, nl) ; stacked image mean
imageDev = fltarr(ns, nl)  ; image difference
imageFloat = fltarr(ns, nl) ; converting floating point


FOR i=0, count-1 DO BEGIN

      Image = READ_TIFF(file[i])
      imageFloat = float(reform(Image))

      Volume[*,*,i] = imageFloat
      imageMean = total(Volume, 3)/nImages
      imageDev = imageFloat - imageMean

         FILE_MKDIR, 'C:\DataProcessing\Images\Temp\'
         outdir = 'C:\DataProcessing\Images\Temp\'
         basename = File_BaseName(file, '.tif')
         outfile = outdir + basename + '.dev.dat'

          OPENW, LUN, (outfile[i]), /GET_LUN
          WRITEU, LUN, imageDev
          FREE_LUN, LUN

ENDFOR

END
;----------------------------------------------------------------------------

I am not sure, but it seems strange that you're calculating imageMean
inside the loop, as you fill Volume up with images.... so imageMean is
different for each value of i... is that what you want?


I think you want to loop over i and fill Volume all the way. Then:

imageMean = total(Volume, 3)/nImages     ;;;<-- nImages is the same as
count, right?
meanVol=rebin(imageMean, ns, nl, count)
devVol=Volume-meanVol

then write each slice of devVol out to a file...

but I could have misunderstood what you want to do...

G

On Jul 4, 12:46=A0am, Gianguido Cianci <gianguido.cia...@gmail.com>
wrote:
> I am not sure, but it seems strange that you're calculating imageMean
> inside the loop, as you fill Volume up with images.... so imageMean is
> different for each value of i... is that what you want?
>
> I think you want to loop over i and fill Volume all the way. Then:
>
> imageMean =3D total(Volume, 3)/nImages =A0 =A0 ;;;<-- nImages is the same=
 as
> count, right?
> meanVol=3Drebin(imageMean, ns, nl, count)
> devVol=3DVolume-meanVol
>
> then write each slice of devVol out to a file...
>
> but I could have misunderstood what you want to do...
>
> G

Hi Gianguido,

Thanks for your suggestion.
But I've got exactly same results though.
I've calculated few files using envi bandmath individually, and the
bandmath seems to give right values.
I will keep studying what's wrong on my code is.

Thanks,
Hojin