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/* RCSid $Id: interp2d.h,v 2.5 2013/02/11 23:33:35 greg Exp $ */ |
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/* |
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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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|
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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 dmin; /* minimum diameter (default=1) */ |
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float smf; /* smoothing factor (def=NI2DSMF) */ |
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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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/* Set minimum distance under which samples will start to merge */ |
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extern void interp2_spacing(INTERP2 *ip, double mind); |
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/* Modify smoothing parameter by the given factor */ |
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extern void interp2_smooth(INTERP2 *ip, double sf); |
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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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/*************************************************************** |
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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 |
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* values in a vector sum that interpolates the function at |
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* that location. |
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* The minimum distance between sample positions defaults to 1.0. |
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* Values spaced closer than this will be merged/averaged. |
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* The interp2_spacing() call may be used to alter this distance, |
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* causing the interpolant to be recalculated during the |
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* next call to the sampling functions. |
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* The default smoothing factor NI2DSMF provides near-optimal |
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* interpolation when well-separated values are known |
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* precisely. Increase this setting by a factor > 1 |
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* with the interp2_smooth() call if greater mixing is desired. |
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* A call of interp2_smooth(ip,0) resets to the minimum |
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* default. It is not possible to "sharpen" the data. |
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**************************************************************/ |
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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_ */ |
