Size (in bytes) of array containing filter weights.

b_value

"B" parameter in the formula for a Mitchell bicubic.

c_value

"C" parameter in the formula for a Mitchell bicubic.

sigma

Standard deviation for a Gaussian.

DESCRIPTION

These routines can be used to initialize filter weight tables for use
with vpSetFilter and vpResample. See the
vpSetFilter man page for information on the num_taps and
num_phases arguments.

vpBoxFilter creates a filter table for a box filter (a zero-order
filter). With num_taps equal to 1 the filter is a
nearest-neighbor filter, suitable for low-quality upsampling. To
create a decimation filter that averages down, the number of taps
should equal the decimation factor (as nearly as possible).

vpLinearFilter creates a filter table for a linear filter (a
first-order or tent filter). With num_taps equal to 2 the
filter performs linear interpolation.

vpBicubicFilter creates a filter table for a Mitchell
bicubic filter. The first two arguments can be used to modify the
shape of the filter kernel. Some standard parameter values are:

b_value = 1, c_value = 0

Cubic B-spline.

b_value = 0, c_value = 0.5

Catmull-Rom spline.

With four filter taps the cubic B-spline filter is suitable for
upsampling. For more details, see the following paper: Mitchell,
D.P. and Netravali, A.N., "Reconstruction filters in computer graphics,"
Proc. SIGGRAPH '88 (Computer Graphics V22 N4), p. 221-8.

vpGaussianFilter creates a filter table for a gaussian filter.
The first argument is the standard deviation of the gaussian.

ERRORS

The normal return value is VP_OK. The following error return values
are possible:

VPERROR_BAD_SIZE

The filter weight table size is invalid.

VPERROR_BAD_VALUE

The number of phases is not a positive power of two.