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      Read part of a large image.


Calling Sequence

      out = imgread( x1, y1, [x2, y2])


      x1 = starting pixel (first=0). in
      y1 = starting image line (first=0). in
      x2 = optional last pixel. in
      y2 = optional last image line. in

Keyword Parameters


        SS=ss subsample factor for x and y (1=every pixel=def).
        XSS=sx subsample factor in x.
        YSS=sy subsample factor in y.
        NX=nx number of output pixels in x (def=512).
        NY=ny number of output pixels in y (def=512).
        /REBIN means average pixels instead of subsampling.
          The averaged image will appear shifted from the
          subsampled image by an amount depending on the number
          of pixels averaged. This happens because the subsampled
          pixels are from the lower left corner of the averaged
        VALUE=v value for out-of-range parts of subimage (def=0).
          If VALUE is not given then output image is trimmed
          to be within the image being read.
        ERROR=err error flag.
            0: OK, -1: part of subimage falls outside main image.
            -2: not open for read, -3: parameter value error.
        SHOW=s print a dot after every s lines is read.
        /EXAMPLES lists some example calls.
        /DEBUG does a debug stop.


Common Blocks



      Notes: Image opened by IMGREAD. Image need not be closed.
        If x2, y2 are given they take precedence over NX and NY.
        If x2, y2 are given and subsample factor is not 1 then
          x2, y2 may not be included in output image.

Modification History

      Ray Sterner, 13 Mar, 1991
      R. Sterner, 17 Sep, 1991 --- added /REBIN, modified common.
  Copyright (C) 1991, Johns Hopkins University/Applied Physics Laboratory
  This software may be used, copied, or redistributed as long as it is not
  sold and this copyright notice is reproduced on each copy made. This
  routine is provided as is without any express or implied warranties
  whatsoever. Other limitations apply as described in the file disclaimer.txt.

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