include/basegfx/utils/keystoplerp.hxx

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  19
  20 #ifndef INCLUDED_BASEGFX_UTILS_KEYSTOPLERP_HXX
  21 #define INCLUDED_BASEGFX_UTILS_KEYSTOPLERP_HXX
  22
  23 #include <vector>
  24 #include <basegfx/basegfxdllapi.h>
  25
  26 namespace com{ namespace sun{ namespace star{ namespace uno {
  27     template<typename T> class Sequence;
  28 }}}}
  29
  30 namespace basegfx
  31 {
  32     namespace utils
  33     {
  34         /** Lerp in a vector of key stops
  35
  36             This class holds a key stop vector and provides the
  37             functionality to lerp inside it. Useful e.g. for
  38             multi-stop gradients, or the SMIL key time activity.
  39
  40             For those, given a global [0,1] lerp alpha, one need to
  41             find the suitable bucket index from key stop vector, and
  42             then calculate the relative alpha between the two buckets
  43             found.
  44          */
  45         class BASEGFX_DLLPUBLIC KeyStopLerp
  46         {
  47         public:
  48             typedef std::pair<std::ptrdiff_t,double> ResultType;
  49
  50             /** Create lerper with given vector of stops
  51
  52                 @param rKeyStops
  53
  54                 Vector of stops, must contain at least two elements
  55                 (though preferably more, otherwise you probably don't
  56                 need key stop lerping in the first place). All
  57                 elements must be of monotonically increasing value.
  58              */
  59             explicit KeyStopLerp( const std::vector<double>& rKeyStops );
  60
  61             /** Create lerper with given sequence of stops
  62
  63                 @param rKeyStops
  64
  65                 Sequence of stops, must contain at least two elements
  66                 (though preferably more, otherwise you probably don't
  67                 need key stop lerping in the first place). All
  68                 elements must be of monotonically increasing value.
  69              */
  70             explicit KeyStopLerp( const css::uno::Sequence<double>& rKeyStops );
  71
  72             /** Find two nearest bucket index & interpolate
  73
  74                 @param fAlpha
  75                 Find bucket index i, with keyStops[i] < fAlpha <=
  76                 keyStops[i+1]. Return new alpha value in [0,1),
  77                 proportional to fAlpha's position between keyStops[i]
  78                 and keyStops[i+1]
  79              */
  80             ResultType lerp(double fAlpha) const;
  81
  82         private:
  83             std::vector<double>    maKeyStops;
  84             mutable std::ptrdiff_t mnLastIndex;
  85         };
  86     }
  87 }
  88
  89 #endif
  90
  91 /* vim:set shiftwidth=4 softtabstop=4 expandtab: */