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NDF_CHUNK
- Obtain an NDF section containing a chunk of contiguous pixels
- Description:
The routine returns an identifier for an NDF section describing a
"chunk" of contiguous pixels selected from an initial NDF. The
routine divides the initial NDF logically into a series of such
chunks, each of which follows immediately on from the previous
chunk, and each of which contains no more than a specified
maximum number (MXPIX) of contiguous pixels. The routine's ICHUNK
argument allows one of these chunks to be selected; an NDF
section for it is then returned.
- Invocation:
CALL NDF_CHUNK( INDF1, MXPIX, ICHUNK, INDF2, STATUS )
- Arguments:
-
INDF1 = INTEGER (Given)
-
Identifier for the initial NDF.
-
MXPIX = INTEGER (Given)
-
Maximum number of contiguous pixels required in each chunk.
-
ICHUNK = INTEGER (Given)
-
Number of the chunk required (the first chunk is numbered 1).
-
INDF2 = INTEGER (Returned)
-
Identifier for an NDF section describing the chunk.
-
STATUS = INTEGER (Given and Returned)
-
The global status.
- Notes:
-
This routine is intended to allow large NDFs to be processed
in smaller pieces by selecting successive chunks, each of which
may then be processed individually. Note that in general not all
the chunks selected from an NDF will have the same size, although
none will contain more than the specified maximum number of
pixels.
-
Corresponding chunks selected from different NDFs (or NDF
sections) with identical shapes will themselves have identical
shapes and will contain the same number of pixels.
-
All NDF sections obtained via this routine have the same number
of dimensions as the input NDF.
-
If the number of the requested chunk (ICHUNK) exceeds the
number of chunks available in the NDF, then a value of NDF__NOID
will be returned for the INDF2 argument (but no error will
result). This condition may be used to terminate a loop when all
available chunks have been processed. The NDF_NCHNK routine may
also be used to determine the number of chunks available.
-
If this routine is called with STATUS set, then a value of
NDF__NOID will be returned for the INDF2 argument, although no
further processing will occur. The same value will also be
returned if the routine should fail for any reason.
-
The NDF__NOID constant is defined in the include file NDF_PAR.
Next: NDF_CINP - Obtain an NDF character component value via the ADAM parameter system
Up: FORTRAN ROUTINE DESCRIPTIONS
Previous: NDF_CGET - Obtain the value of an NDF character component
Starlink User Note 33
R.F. Warren-Smith
11th January 2000
E-mail:rfws@star.rl.ac.uk
Copyright © 2000 Council for the Central Laboratory of the Research Councils