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/* RCSid $Id$ */ |
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/* |
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* Header for interpolation of anisotropic values on 2-D plane. |
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* Header for interpolation of anisotropic samples on 2-D plane. |
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* |
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* G.Ward Feb 2013 |
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*/ |
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#define NI2DSMF 0.42f /* minimal smoothing radius */ |
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#ifndef _RAD_INTERP2D_H_ |
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#define _RAD_INTERP2D_H_ |
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#ifdef __cplusplus |
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extern "C" { |
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#endif |
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#define NI2DSMF 0.42f /* minimal smoothing factor */ |
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#define NI2DIR (2*4) /* # interpolation directions */ |
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/* Data structure for interpolant */ |
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typedef struct { |
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int ns; /* number of sample positions */ |
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float rmin; /* minimum valid radius (default=.5) */ |
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float dmin; /* minimum diameter (default=1) */ |
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float smf; /* smoothing factor (def=NI2DSMF) */ |
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unsigned short (*ra)[NI2DIR]; /* anisotropic radii (private) */ |
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unsigned short (*da)[NI2DIR]; /* anisotropic distances (private) */ |
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float spt[1][2]; /* sample positions (extends struct) */ |
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} INTERP2; |
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/* Allocate a new set of interpolation samples (caller assigns spt[] array) */ |
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extern INTERP2 *interp2_alloc(int nsamps); |
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/* Resize interpolation array (caller must assign any new values) */ |
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extern INTERP2 *interp2_realloc(INTERP2 *ip, int nsamps); |
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/* Assign full set of normalized weights to interpolate the given location */ |
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extern int interp2_weights(float wtv[], INTERP2 *ip, double x, double y); |
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/* Get normalized weights and indexes for n best samples in descending order */ |
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extern int interp2_topsamp(float wt[], int si[], const int n, |
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INTERP2 *ip, double x, double y); |
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/* Free interpolant */ |
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extern void interp2_free(INTERP2 *ip); |
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/* (Re)compute anisotropic basis function interpolant (normally automatic) */ |
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extern int interp2_analyze(INTERP2 *ip); |
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/*************************************************************** |
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* Typical use is to allocate an INTERP2 struct and assign the |
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* spt[] array with the ordered sample locations in x & y. (The |
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* actual orientation of the axes is not important so long as |
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* the application is consistent.) During interpolation, either |
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* interp2_weights() is called to obtain a normalized weighting |
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* vector for all the samples, or interp2_topsamp() is called to |
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* get the most important N samples for the specified location. |
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* The weights (and indexes in the case of interp2_topsamp) |
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* are then used as coefficients for corresponding sample values |
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* in a vector sum together that interpolates the function at that |
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* location. Between the initial allocation call and the first |
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* weight evaluation, the dmin member may be adjusted to |
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* the distance under which samples will start to merge. If this |
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* parameter is later changed, interp2_analyze() should be called |
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* to recompute the interpolant. |
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* The smf member sets the smoothing factor for interpolation. |
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* The default setting of NI2DSMF produces near-optimal |
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* interpolation when well-separated sample values are known |
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* precisely. If a greater degree of mixing is desired, this |
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* paremter may be increased and it will affect the next call |
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* to interp2_weights() or interp2_topsamp(). |
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**************************************************************/ |
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#ifdef __cplusplus |
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} |
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#endif |
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#endif /* !_RAD_INTERP2D_H_ */ |
