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.