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.
