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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 .
+ */
+
+#ifndef INCLUDED_VCL_RESAMPLEKERNEL_HXX
+#define INCLUDED_VCL_RESAMPLEKERNEL_HXX
+
+#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
+
+#endif // INCLUDED_VCL_RESAMPLEKERNEL_HXX
+
+/* vim:set shiftwidth=4 softtabstop=4 expandtab: */