
MIDAS recognizes images and tables which have been compressed with the
commands `compress' or `gzip'. Compressed files are detected via the appended
".Z" (compress) or ".gz" (gzip) to the original file name. These files are 
decompressed on the fly, the MIDAS command uses the uncompressed file and 
finally the file is compressed again.

E.g.  

Midas 031> $ls *.mt*
galaxy.mt.Z milky_way.bdf.gz
Midas 032> load/image galaxy.mt.Z
Midas 033> write/descr milky_way.bdf.gz newdesc/c/1/11 "this is new"
Midas 034> $ls *.mt*
galaxy.mt.Z milky_way.bdf.gz

This will uncompress the FITS file galaxy.mt.Z via `uncompress' to obtain 
galaxy.mt; load this FITS file into a display window; and finally compress 
galaxy.mt via `compress' to get again the file galaxy.bdf.Z .
Also the Midas image milky_way.bdf.gz is uncompressed via `gzip'; the image
milky_way.bdf is used in the WRITE/DESCR command and the updated image is
compressed via `gzip -d' to yield milky_way.bdf.gz again. 

The keyword AUX_MODE(21) controls the final recompression. 
AUX_MODE(21) = 0 (the default) will result in the recompression of the 
uncompressed file via the original compression command.
AUX_MODE(21) = 1 will leave the uncompressed files as they are.

Midas 030> AUX_MODE(21) = 1
Midas 031> $ls *.mt*
galaxy.mt.Z  milky_way.bdf.gz
Midas 032> load/image galaxy.mt.Z
Midas 033> write/descr milky_way.bdf.gz newdesc/c/1/11 "this is new"
Midas 034> $ls *.mt*
galaxy.mt  milky_way.bdf

