array_interpolator2.h

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/*
**  array_interpolator2.h
**
**  This is part of Shiokaze, a research-oriented fluid solver for computer graphics.
**  Created by Ryoichi Ando <rand@nii.ac.jp> on Feb 14, 2018.
**
**  Permission is hereby granted, free of charge, to any person obtaining a copy of
**  this software and associated documentation files (the "Software"), to deal in
**  the Software without restriction, including without limitation the rights to use,
**  copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the
**  Software, and to permit persons to whom the Software is furnished to do so,
**  subject to the following conditions:
**
**  The above copyright notice and this permission notice shall be included in all copies
**  or substantial portions of the Software.
**
**  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED,
**  INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A
**  PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
**  HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF
**  CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE
**  OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
*/
//
#ifndef SHKZ_ARRAY_INTERPOLATOR2_H
#define SHKZ_ARRAY_INTERPOLATOR2_H
//
#include "array2.h"
#include <cmath>
#include <cstdlib>
//
SHKZ_BEGIN_NAMESPACE
//
namespace array_interpolator2 {
    static void interpolate_coef( const shape2 &shape, const vec2d &p, vec2i indices[4], double coef[4] ) {
        double x = std::max(0.0,std::min(shape.w-1.,p[0]));
        double y = std::max(0.0,std::min(shape.h-1.,p[1]));
        int i = std::min(x,shape.w-2.);
        int j = std::min(y,shape.h-2.);
        indices[0] = vec2i(i,j);
        indices[1] = vec2i(i+1,j);
        indices[2] = vec2i(i,j+1);
        indices[3] = vec2i(i+1,j+1);
        coef[0] = (i+1-x)*(j+1-y);
        coef[1] = (x-i)*(j+1-y);
        coef[2] = (i+1-x)*(y-j);
        coef[3] = (x-i)*(y-j);
    }
    template<class T> T static interpolate( const array2<T> &array, const vec2d &p, bool only_actives=false ) {
        T values[4]; vec2i indices[4]; double coef[4];
        interpolate_coef(array.shape(),p,indices,coef);
        T value = T();
        if( only_actives ) {
            double w[4];
            double sum (0.0);
            for( int n=0; n<4; ++n ) w[n] = array.active(indices[n]) ? coef[n] : 0.0;
            for( int n=0; n<4; ++n ) sum += w[n];
            if( sum ) {
                for( int n=0; n<4; ++n ) w[n] /= sum;
                for( unsigned n=0; n<4; ++n ) if( w[n] ) value += array(indices[n]) * w[n];
            }
        } else {
            for( unsigned n=0; n<4; ++n ) if( coef[n] ) value += array(indices[n]) * coef[n];
        }
        return value;
    }
    template<class T> T static interpolate( const array2<T> &array, const vec2d &origin, double dx, const vec2d &p, bool only_actives=false ) {
        return interpolate<T>(array,(p-origin)/dx,only_actives);
    }
};
//
SHKZ_END_NAMESPACE
//
#endif
//