include/basegfx/utils/keystoplerp.hxx

   1 /* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
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  19
  20 #pragma once
  21
  22 #include <vector>
  23 #include <basegfx/basegfxdllapi.h>
  24
  25 namespace com::sun::star::uno {
  26     template<typename T> class Sequence;
  27 }
  28
  29 namespace basegfx::utils
  30 {
  31         /** Lerp in a vector of key stops
  32
  33             This class holds a key stop vector and provides the
  34             functionality to lerp inside it. Useful e.g. for
  35             multi-stop gradients, or the SMIL key time activity.
  36
  37             For those, given a global [0,1] lerp alpha, one need to
  38             find the suitable bucket index from key stop vector, and
  39             then calculate the relative alpha between the two buckets
  40             found.
  41          */
  42         class BASEGFX_DLLPUBLIC KeyStopLerp
  43         {
  44         public:
  45             typedef std::pair<std::ptrdiff_t,double> ResultType;
  46
  47             /** Create lerper with given vector of stops
  48
  49                 @param rKeyStops
  50
  51                 Vector of stops, must contain at least two elements
  52                 (though preferably more, otherwise you probably don't
  53                 need key stop lerping in the first place). All
  54                 elements must be of monotonically increasing value.
  55              */
  56             explicit KeyStopLerp( std::vector<double>&& rKeyStops );
  57
  58             /** Create lerper with given sequence of stops
  59
  60                 @param rKeyStops
  61
  62                 Sequence of stops, must contain at least two elements
  63                 (though preferably more, otherwise you probably don't
  64                 need key stop lerping in the first place). All
  65                 elements must be of monotonically increasing value.
  66              */
  67             explicit KeyStopLerp( const css::uno::Sequence<double>& rKeyStops );
  68
  69             /** Find two nearest bucket index & interpolate
  70
  71                 @param fAlpha
  72                 Find bucket index i, with keyStops[i] < fAlpha <=
  73                 keyStops[i+1]. Return new alpha value in [0,1),
  74                 proportional to fAlpha's position between keyStops[i]
  75                 and keyStops[i+1]
  76              */
  77             ResultType lerp(double fAlpha) const;
  78
  79         private:
  80             std::vector<double>    maKeyStops;
  81             mutable std::ptrdiff_t mnLastIndex;
  82         };
  83 }
  84
  85 /* vim:set shiftwidth=4 softtabstop=4 expandtab: */