readenvi

  reads ENVI standard format image files

          $im = readenvi( filename );  # read image data
  ($im, $hdr) = readenvi( filename );  # read image data and hdr data hashref
  
  readenvi will look for an ENVI header file named filename.hdr
  
  If that file is not found, it will try with the windows
  convention of replacing the suffix of the filename by .hdr
  
  If valid header data is found, the image will be read and
  returned, with a ref to a hash of the hdr data in list
  context.
  
  NOTE: This routine only supports raw binary data at this time.