- list the active elements at a specified pyramid layer
long *cxPyrActiveList(cxPyramid *pyr, long dstLayer, long *numActive)
integer function cxPyrActiveList( pyr, dstLayer, numActive )
Input pyramid structure for which computations are to be performed.
Input layer of next active elements (1-based value).
Output number of active elements in returned array at layer dstLayer.
FUNCTION RETURN VALUE
Returns a pointer to a long array of indices of active elements
in layer dstLayer, given that all elements at the top layer of the
input pyramid are active.
Returns a NULL if its input is malformed, if an allocation error occurs, or
if the destination layer is in a compressed region. Returns a list of active
vertices if dstLayer is zero, even in the presence of compression.
cxPyrActiveList computes which subordinate elements are
active at the layer dstLayer. This is an index vector of all
elements that can be reached from the top of the input pyramid.
cxPyrActiveList is useful in circumstances where only the active
elements at a given level are to be manipulated.
This is the approved way of determining the pyramid elements which
should be manipulated or displayed in any pyramid-based module (the
alternative method of displaying all elements available at a given
level is not correct).
The returned index array is considered to be owned by the caller
of cxPyrActiveList and should be freed (with free(3C)) after use.
Other routines exist to flag elements at a specified layer as active/inactive and
to return a variable-length array of the indices of active elements subordinate to
the current layer.
Last modified: Mon Nov 6 16:33:41 GMT 2000
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© The Numerical Algorithms Group Ltd, Oxford UK. 1999