This is a fictitious routine which does not actually
exist. Instead, this description constitutes a template so that
you may implement a routine with this interface for yourself
(and give it any name you wish). Such a routine
may be passed via the FINTERP argument of the AST_RESAMPLE
X
functions (q.v.) in order to supply a 1-dimensional
interpolation kernel to the algorithm which performs sub-pixel
interpolation during resampling of gridded data (you must also
set the INTERP argument of AST_RESAMPLE
X
to the value
AST__UKERN1). This allows you to use your own interpolation
kernel in addition to those which are pre-defined.
The routine calculates the value of a 1-dimensional sub-pixel
interpolation kernel. This determines how the weight given to
neighbouring pixels in calculating an interpolated value depends
on the pixel's offset from the interpolation point. In more than
one dimension, the weight assigned to a pixel is formed by
evaluating this 1-dimensional kernel using the offset along each
dimension in turn. The product of the returned values is then
used as the pixel weight.