basegfx/source/tools/keystoplerp.cxx

   1 /* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
   2 /*
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   6  * License, v. 2.0. If a copy of the MPL was not distributed with this
   7  * file, You can obtain one at http://mozilla.org/MPL/2.0/.
   8  *
   9  * This file incorporates work covered by the following license notice:
  10  *
  11  *   Licensed to the Apache Software Foundation (ASF) under one or more
  12  *   contributor license agreements. See the NOTICE file distributed
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  14  *   ownership. The ASF licenses this file to you under the Apache
  15  *   License, Version 2.0 (the "License"); you may not use this file
  16  *   except in compliance with the License. You may obtain a copy of
  17  *   the License at http://www.apache.org/licenses/LICENSE-2.0 .
  18  */
  19
  20 #include <basegfx/utils/keystoplerp.hxx>
  21 #include <com/sun/star/uno/Sequence.hxx>
  22 #include <osl/diagnose.h>
  23
  24 #include <algorithm>
  25
  26 static void validateInput(const std::vector<double>& rKeyStops)
  27 {
  28 #ifdef DBG_UTIL
  29     OSL_ENSURE( rKeyStops.size() > 1,
  30                 "KeyStopLerp::KeyStopLerp(): key stop vector must have two entries or more" );
  31
  32     // rKeyStops must be sorted in ascending order
  33     for( std::size_t i=1, len=rKeyStops.size(); i<len; ++i )
  34     {
  35         if( rKeyStops[i-1] > rKeyStops[i] )
  36             OSL_FAIL( "KeyStopLerp::KeyStopLerp(): time vector is not sorted in ascending order!" );
  37     }
  38 #else
  39     (void)rKeyStops;
  40 #endif
  41 }
  42
  43 namespace basegfx::utils
  44 {
  45         KeyStopLerp::KeyStopLerp( std::vector<double>&& rKeyStops ) :
  46             maKeyStops(std::move(rKeyStops)),
  47             mnLastIndex(0)
  48         {
  49             validateInput(maKeyStops);
  50         }
  51
  52         KeyStopLerp::KeyStopLerp( const ::css::uno::Sequence<double>& rKeyStops ) :
  53             maKeyStops(rKeyStops.begin(), rKeyStops.end()),
  54             mnLastIndex(0)
  55         {
  56             validateInput(maKeyStops);
  57         }
  58
  59         KeyStopLerp::ResultType KeyStopLerp::lerp(double fAlpha) const
  60         {
  61             // cached value still okay?
  62             if( maKeyStops.at(mnLastIndex) < fAlpha ||
  63                 maKeyStops.at(mnLastIndex+1) >= fAlpha )
  64             {
  65                 // nope, find new index
  66                 mnLastIndex = std::min<std::ptrdiff_t>(
  67                     maKeyStops.size()-2,
  68                     // range is ensured by max below
  69                     std::max<std::ptrdiff_t>(
  70                         0,
  71                         std::distance( maKeyStops.begin(),
  72                                        std::lower_bound( maKeyStops.begin(),
  73                                                          maKeyStops.end(),
  74                                                          fAlpha )) - 1 ));
  75             }
  76
  77             // lerp between stop and stop+1
  78             const double fRawLerp=
  79                 (fAlpha-maKeyStops.at(mnLastIndex)) /
  80                 (maKeyStops.at(mnLastIndex+1) - maKeyStops.at(mnLastIndex));
  81
  82             // clamp to permissible range (input fAlpha might be
  83             // everything)
  84             return ResultType(
  85                 mnLastIndex,
  86                 std::clamp(fRawLerp,0.0,1.0));
  87         }
  88 }
  89
  90 /* vim:set shiftwidth=4 softtabstop=4 expandtab: */