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vpBoxFilter(3) Library Functions Manual vpBoxFilter(3) NAME vpBoxFilter, vpLinearFilter, vpBicubicFilter, vpGaussianFilter - ini- tialize a filter weight table SYNOPSIS #include <volpack.h> vpResult vpBoxFilter(num_taps, num_phases, weights, weights_bytes) int num_taps, num_phases; float *weights; int weights_bytes; vpResult vpLinearFilter(num_taps, num_phases, weights, weights_bytes) int num_taps, num_phases; float *weights; int weights_bytes; vpResult vpBicubicFilter(b_value, c_value, num_taps, num_phases, weights, weights_bytes) double b_value, c_value; int num_taps, num_phases; float *weights; int weights_bytes; vpResult vpGaussianFilter(sigma, num_taps, num_phases, weights, weights_bytes) double sigma; int num_taps, num_phases; float *weights; int weights_bytes; ARGUMENTS num_taps Number of filter taps. num_phases Number of filter phases. weights Array containing filter weights. weights_bytes 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 in- formation on the num_taps and num_phases arguments. vpBoxFilter creates a filter table for a box filter (a zero-order fil- ter). With num_taps equal to 1 the filter is a nearest-neighbor fil- ter, suitable for low-quality upsampling. To create a decimation fil- ter 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-or- der or tent filter). With num_taps equal to 2 the filter performs lin- ear 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 upsam- pling. 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. SEE ALSO VolPack(3), vpResample(3), vpSetFilter(3) VolPack vpBoxFilter(3)
NAME | SYNOPSIS | ARGUMENTS | DESCRIPTION | ERRORS | SEE ALSO
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