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

196 CHAPTER 16. DATA STRUCTURE MANIPULATION
Alternatively, you can extract the dead pixels from an SCD directly:
CIA> dead_mask = scd_get( ’mask.dead’, ’CSCD143006010110_97092611592803’ )
16.4.2 Modifying the MASK
Following on from Section 16.4.1 we will now create and modify our own MASK.
1. Firstly, create an empty array that will hold our MASK, let’s call this our mask. We will
makeitthesamesizeasoriginal mask:
CIA> our_mask = bytarr(32,32,19)
2. Suppose that the first column of all our CAM IMAGEs is blind, we can set the first column
pixels to the appropriate value with put mask.
CIA> our_mask[0,*,*] = put_mask( ’blind’, our_mask[0,*,*] )
3. Now look at the first element in our mask. This should be a blind pixel.
CIA> print, our_mask[0]
16
Since it is a blind pixel it has a value of 16.
4. Our MASK can be added to a CIA structure with scd put. The keyword put decides how
out MASK is inserted into the structure. For example, to combine the MASK bits in our
MASK with the CIA structure’s existing MASK bits, i.e an OR operation:
CIA> scd_put, ’mask’, mask, ’CSCD143006010110_97092611592803’, put=’put’
Actually this is the default behaviour of scd put. To replace the existing MASK with the
input MASK then put should be set to ‘set’. Setting put to ‘clear’ will cause the existing
MASK bits to be set to zero (i.e. cleared) where the input MASK bits are one.
Alternatively, we can create a MASK and put it directly into a structure, merging it with
the structure’s MASK. The structure could be a PDS or ordinary structure extracted from a
CIA structure, e.g.
CIA> struct = scd_extract( ’CSCD143006010110_97092611592803’ )
Now follow the following procedure.
1. Create a variable to hold our MASK.
CIA> our_mask = bytarr(32,32,19)
2. set the pixels we wanted masked to 1. Again we use the example that the first column of
all our CAM IMAGEs are blind.
CIA> our_mask[0,*,*] = 1
3. Call ia put mask to put our mask into struct, converting the pixels of value of 1 to the
appropriate value for blind pixels.
CIA> ia_put_mask, ’blind’, struct, our_mask