ISOCAM Interactive Analysis User's Manual Version 5.0 - ISO - ESA

16.4. MANIPULATING THE MASK 195
and .CUBE – these fields contains the vast bulk of the data in a PDS, so removing them greatly
decreases the PDS size and saves disk and memory space.
CIA> raster_pds = prune_pds( raster_pds )
CIA> save, file=’raster_pds.dat’, raster_pds, /verb
% SAVE: Portable (XDR) SAVE/RESTORE file.
% SAVE: Saved variable: raster_pds.
raster pds is a raster PDS which is originally more than 2 MB in size. prune pds reduces
it to about 0.5 MB.
CIA> $ls -la raster_pds.dat
-rw-r--r-- 1 mdelaney ssamr 500568 Oct 14 13:17 raster_pds.dat
16.4 Manipulating the MASK
This section describes CIA MASK manipulation routines. For more details on the MASK in
CIA data structures and a list of the possible MASK values see Section 15.2.2.18. Also take a
look at Section 2.3.4 for how to configure the MASK handling.
• ia put mask routine to modify the MASK in a CIA data structure or IDL array. To work
with ordinary IDL arrays you can use put mask.
• ia get mask routine to extract the MASK from a CIA data structure.
16.4.1 Extracting the MASK from CIA data structures
Follow the procedure below to extract and examine a MASK from a CIA data structure.
1. Suppose we have a CIA structure. The first step is to extract the entire MASK from the
structure.
• If our structure was an SCD this can be done as:
CIA> mask = scd_get( ’mask’, ’CSCD143006010110_97092611592803’ )
• If it is a PDS:
CIA> mask = pds.mask
2. Now, to look at the dead pixels use ia get mask to extract and tviso to display.
CIA> dead_mask = ia_get_mask( ’dead’, mask )
CIA> tviso, dead_mask[*,*,0]
If you look at the values in dead mask you will see that they are either 0 or 1. However
the values in original mask can be 0,1,2,4,6,8,16,32,64,128, each value having a separate
meaning (see the table in Section 15.2.2.18). ia get mask translates these values to a simple
0 or 1. In our example above, we asked for the pixels masked as dead to be translated, so
all the pixels with a value of 2 in original mask became 1 in dead mask.