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/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
/*
* This file is part of the LibreOffice project.
*
* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/.
*
* This file incorporates work covered by the following license notice:
*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed
* with this work for additional information regarding copyright
* ownership. The ASF licenses this file to you under the Apache
* License, Version 2.0 (the "License"); you may not use this file
* except in compliance with the License. You may obtain a copy of
* the License at http://www.apache.org/licenses/LICENSE-2.0 .
*/
#pragma once
#include <boost/math/special_functions/sinc.hpp>
namespace vcl {
// Resample kernels
class Kernel
{
public:
Kernel() {}
virtual ~Kernel() {}
virtual double GetWidth() const = 0;
virtual double Calculate( double x ) const = 0;
};
class Lanczos3Kernel final : public Kernel
{
public:
Lanczos3Kernel() : Kernel () {}
virtual double GetWidth() const override { return 3.0; }
virtual double Calculate (double x) const override
{
return (-3.0 <= x && x < 3.0) ? SincFilter(x) * SincFilter( x / 3.0 ) : 0.0;
}
static double SincFilter(double x)
{
if (x == 0.0)
{
return 1.0;
}
x = x * M_PI;
return boost::math::sinc_pi(x, SincPolicy());
}
private:
typedef boost::math::policies::policy<
boost::math::policies::promote_double<false> > SincPolicy;
};
class BicubicKernel final : public Kernel
{
public:
BicubicKernel() : Kernel () {}
private:
virtual double GetWidth() const override { return 2.0; }
virtual double Calculate (double x) const override
{
if (x < 0.0)
{
x = -x;
}
if (x <= 1.0)
{
return (1.5 * x - 2.5) * x * x + 1.0;
}
else if (x < 2.0)
{
return ((-0.5 * x + 2.5) * x - 4) * x + 2;
}
return 0.0;
}
};
class BilinearKernel final : public Kernel
{
public:
BilinearKernel() : Kernel () {}
private:
virtual double GetWidth() const override { return 1.0; }
virtual double Calculate (double x) const override
{
if (x < 0.0)
{
x = -x;
}
if (x < 1.0)
{
return 1.0-x;
}
return 0.0;
}
};
} // namespace vcl
/* vim:set shiftwidth=4 softtabstop=4 expandtab: */
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