LibreOffice Module vcl (master)  1
ResampleKernel.hxx
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19 
20 #ifndef INCLUDED_VCL_RESAMPLEKERNEL_HXX
21 #define INCLUDED_VCL_RESAMPLEKERNEL_HXX
22 
23 #include <boost/math/special_functions/sinc.hpp>
24 
25 namespace vcl {
26 
27 // Resample kernels
28 
29 class Kernel
30 {
31 public:
32  Kernel() {}
33  virtual ~Kernel() {}
34 
35  virtual double GetWidth() const = 0;
36  virtual double Calculate( double x ) const = 0;
37 };
38 
39 class Lanczos3Kernel : public Kernel
40 {
41 public:
43 
44  virtual double GetWidth() const override { return 3.0; }
45  virtual double Calculate (double x) const override
46  {
47  return (-3.0 <= x && x < 3.0) ? SincFilter(x) * SincFilter( x / 3.0 ) : 0.0;
48  }
49 
50  static double SincFilter(double x)
51  {
52  if (x == 0.0)
53  {
54  return 1.0;
55  }
56  x = x * M_PI;
57  return boost::math::sinc_pi(x, SincPolicy());
58  }
59 
60 private:
61  typedef boost::math::policies::policy<
62  boost::math::policies::promote_double<false> > SincPolicy;
63 };
64 
65 class BicubicKernel : public Kernel
66 {
67 public:
69 
70 private:
71  virtual double GetWidth() const override { return 2.0; }
72  virtual double Calculate (double x) const override
73  {
74  if (x < 0.0)
75  {
76  x = -x;
77  }
78 
79  if (x <= 1.0)
80  {
81  return (1.5 * x - 2.5) * x * x + 1.0;
82  }
83  else if (x < 2.0)
84  {
85  return ((-0.5 * x + 2.5) * x - 4) * x + 2;
86  }
87  return 0.0;
88  }
89 };
90 
91 class BilinearKernel : public Kernel
92 {
93 public:
95 
96 private:
97  virtual double GetWidth() const override { return 1.0; }
98  virtual double Calculate (double x) const override
99  {
100  if (x < 0.0)
101  {
102  x = -x;
103  }
104  if (x < 1.0)
105  {
106  return 1.0-x;
107  }
108  return 0.0;
109  }
110 };
111 
112 } // namespace vcl
113 
114 #endif // INCLUDED_VCL_RESAMPLEKERNEL_HXX
115 
116 /* vim:set shiftwidth=4 softtabstop=4 expandtab: */
virtual double GetWidth() const override
virtual double GetWidth() const override
virtual double Calculate(double x) const override
static double SincFilter(double x)
virtual double GetWidth() const =0
virtual double Calculate(double x) const override
virtual double Calculate(double x) const =0
virtual double GetWidth() const override
virtual double Calculate(double x) const override
boost::math::policies::policy< boost::math::policies::promote_double< false > > SincPolicy
virtual ~Kernel()