array_gaussianblur2.h

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/*
**  array_gaussianblur2.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_GAUSSIANBLUR2_H
#define SHKZ_ARRAY_GAUSSIANBLUR2_H
//
#include "shared_array2.h"
#include <cmath>
#include <cstdlib>
//
SHKZ_BEGIN_NAMESPACE
//
namespace array_gaussianblur2 {
    template<class T> void gaussian_blur( const array2<T> &array, array2<T> &result, double r, const bitarray2 *mask=nullptr ) {
        int rs = std::ceil(r * 2.57);
        std::vector<double> exp_w(2*rs+1);
        for(int q=-rs; q<rs+1; q++) {
            exp_w[q+rs] = std::exp(-(q*q)/(2.0*r*r))/std::sqrt(M_PI*2.0*r*r);
        }
        auto valid = [&]( int i, int j ) {
            if( ! mask ) return true;
            else {
                return (*mask)(mask->shape().clamp(i,j)) != 0;
            }
        };
        shared_array2<T> save (array);
        //
        for( int dim : DIMS2 ) {
            result.parallel_all([&](int i, int j, auto &it) {
                if( valid(i,j)) {
                    T val (0.0);
                    double wsum (0.0);
                    for(int q=-rs; q<rs+1; q++) {
                        int ni = i+(dim==0)*q;
                        int nj = j+(dim==1)*q;
                        const double &wght = exp_w[q+rs];
                        if( valid(ni,nj)) {
                            T value = save()(save->shape().clamp(ni,nj));
                            val += value * wght;  wsum += wght;
                        }
                    }
                    if( wsum ) result.set(i,j, val / wsum );
                    else it.set(T(0.0));
                }
            });
            save->copy(result);
        }
    }
};
//
SHKZ_END_NAMESPACE
//
#endif
//