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NDF_BLOCK
- Obtain an NDF section containing a block of adjacent pixels
- Description:
The routine returns an identifier for an NDF section describing a
"block" of adjacent pixels selected from an initial NDF. The
routine divides the original NDF logically into a series of such
blocks, each of which does not exceed a specified maximum number
of pixels in each dimension. The routine's IBLOCK argument
allows one of these blocks to be selected; an NDF section for it
is then returned.
- Invocation:
CALL NDF_BLOCK( INDF1, NDIM, MXDIM, IBLOCK, INDF2, STATUS )
- Arguments:
-
INDF1 = INTEGER (Given)
-
Identifier for the initial NDF.
-
NDIM = INTEGER (Given)
-
Number of maximum dimension sizes.
-
MXDIM( NDIM ) = INTEGER (Given)
-
Array specifying the maximum size of a block in pixels along
each dimension.
-
IBLOCK = INTEGER (Given)
-
Number of the block required (the first block is numbered 1).
-
INDF2 = INTEGER (Returned)
-
Identifier for an NDF section describing the block.
-
STATUS = INTEGER (Given and Returned)
-
The global status.
- Notes:
-
This routine is intended to allow NDFs to be processed in
smaller pieces by selecting successive blocks, each of which may
then be processed individually. Note that in general not all the
blocks selected from an NDF will have the same shape or size,
although none will exceed the specified maximum number of pixels
in each dimension.
-
Corresponding blocks 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 maximum
dimension sizes supplied (NDIM) is less than this number, then a
value of 1 will be used for the extra dimension sizes. If the
value of NDIM is larger than this number, then the excess
dimension sizes will be ignored.
-
If the number of the requested block (IBLOCK) exceeds the
number of blocks 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 blocks have been processed. The NDF_NBLOC routine may
also be used to determine the number of blocks 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_BOUND - Enquire the pixel-index bounds of an NDF
Up: FORTRAN ROUTINE DESCRIPTIONS
Previous: NDF_BEGIN - Begin a new NDF context
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