PiecewiseLinearFct.hpp

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/* ImLib3D
 * Copyright (c) 2001, ULP-IPB Strasbourg.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or (at
 * your option) any later version.
 * 
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License for more details.
 * 
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 */
#ifndef _PiecewiseLinearFct_hpp
#define _PiecewiseLinearFct_hpp

template<class ValueType>
class PiecewiseLinearFct
{
    map<float,ValueType> points;
public:
    ValueType Value(float x) const
    {
        float x0,x1;
        ValueType v0,v1;
        typename map<float,ValueType>::const_iterator lb=points.lower_bound(x);
        if(lb==points.end()  )
        {
            lb--;
            x1=(*lb).first;
            v1=(*lb).second;
            lb--;
            x0=(*lb).first;
            v0=(*lb).second;
        }
        else
        if(lb==points.begin())
        {
            x0=(*lb).first;
            v0=(*lb).second;
            lb++;
            x1=(*lb).first;
            v1=(*lb).second;
        }
        else
        {
            x1=(*lb).first;
            v1=(*lb).second;
            lb--;
            x0=(*lb).first;
            v0=(*lb).second;
        }
        return ((x-x0)/(x1-x0))*(v1-v0)+v0;
    }
    void Plot() const
    {
        vector<double> x,y;

        float x0=(*points.begin()).first;
        float x1=(*--points.end()).first;
        for(float xx=x0-.5*(x1-x0);xx<=x1+.5*(x1-x0);xx+=(x1-x0)/100.0)
        {
            x.push_back(xx);
            y.push_back((*this)(xx));
        }
        GnuPlot(x,y);
    }
    inline ValueType operator()(float x) const {return Value(x);}
    void AddValue(float x,const ValueType &y){points[x]=y;}
    PiecewiseLinearFct(){;}
    PiecewiseLinearFct(const ValueType *init,int n)
    {
        for(int i=0;i<n;i++)
        {
            AddValue((float)init[2*i],init[2*i+1]);
        }
    }
};

typedef  PiecewiseLinearFct<float> PiecewiseLinearFctf;

#endif // _PiecewiseLinearFct_hpp

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