NAME:
  subarr
 PURPOSE:   (one line only)
  Extract a sub-array from an image with bound checking
 DESCRIPTION:
  Return a portion of an image as a sub-array.  The requested location for
    the sub-array is checked against the real boundary of the original image
    and portions of the sub-array that fall off the image are padded out
    with either zeros or a noisy background filler.
  An error is generated only when there is no overlap between the requested
    sub-array and the image.
 CATEGORY:
  Image display
 CALLING SEQUENCE:
  subarr,image,i0,i1,j0,j1,sub,error
 INPUTS:
  image - The input image
  i0    - Bottom of the sub-array location
  i1    - Top of the sub-array location
  j0    - Left boundary of the sub-array location
  j1    - Right boundary of the sub-array location
 OPTIONAL INPUT PARAMETERS:
 KEYWORD INPUT PARAMETERS:
  FILL  - value to use to fill non-overlap regions between sub and image
             (default=0)
  NOISE - noise value for FILL (default=0), this will not always be useful
             for non-floating point data types.
  SEED  - seed value for random number generator.  This is used only when
             NOISE is non-zero.  It is only needed if you are trying to
             create the same set of random values for testing.  Under normal
             circumstances there is no need to ever specify this value.
 OUTPUTS:
  sub   - sub-array from image, if an error occurs this will be returned as
            a scalar zero.
  error - Flag, set if an error occurred.  The only time this happens is if
            the requested area has no overlap with the image.
 KEYWORD OUTPUT PARAMETERS:
 COMMON BLOCKS:
 SIDE EFFECTS:
 RESTRICTIONS:
 PROCEDURE:
 MODIFICATION HISTORY:
  Written by Marc W. Buie, Southwest Research Insitute, 2015/06/30
  2016/12/28, MWB, added byte input option for FILL