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+/*************************************************************************
+ *
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * Copyright 2008 by Sun Microsystems, Inc.
+ *
+ * OpenOffice.org - a multi-platform office productivity suite
+ *
+ * $RCSfile: colortraits.hxx,v $
+ * $Revision: 1.4 $
+ *
+ * This file is part of OpenOffice.org.
+ *
+ * OpenOffice.org is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License version 3
+ * only, as published by the Free Software Foundation.
+ *
+ * OpenOffice.org is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Lesser General Public License version 3 for more details
+ * (a copy is included in the LICENSE file that accompanied this code).
+ *
+ * You should have received a copy of the GNU Lesser General Public License
+ * version 3 along with OpenOffice.org.  If not, see
+ * <http://www.openoffice.org/license.html>
+ * for a copy of the LGPLv3 License.
+ *
+ ************************************************************************/
+
+#ifndef INCLUDED_BASEBMP_COLORTRAITS_HXX
+#define INCLUDED_BASEBMP_COLORTRAITS_HXX
+
+#include <basebmp/accessoradapters.hxx>
+#include <basebmp/metafunctions.hxx>
+
+#include <vigra/mathutil.hxx>
+
+namespace basebmp
+{
+
+/** Functor template, to calculate alpha blending between two
+    values. Float case.
+
+    @tpl polarity
+    When true, 0 means fully transparent, and 1 fully opaque. And vice
+    versa.
+ */
+template< typename ValueType,
+          typename AlphaType,
+          bool     polarity > struct BlendFunctor;
+template< typename ValueType,
+          typename AlphaType > struct BlendFunctor<ValueType,AlphaType,true>
+  : public TernaryFunctorBase<AlphaType,ValueType,ValueType,ValueType>
+{
+    ValueType operator()( AlphaType alpha,
+                          ValueType v1,
+                          ValueType v2 ) const
+    {
+        const typename vigra::NumericTraits<AlphaType>::RealPromote fAlpha(
+            vigra::NumericTraits<AlphaType>::toRealPromote(alpha));
+        return (vigra::NumericTraits<AlphaType>::one()-fAlpha)*v1 + fAlpha*v2;
+    }
+};
+template< typename ValueType,
+          typename AlphaType > struct BlendFunctor<ValueType,AlphaType,false>
+  : public TernaryFunctorBase<AlphaType,ValueType,ValueType,ValueType>
+{
+    ValueType operator()( AlphaType alpha,
+                          ValueType v1,
+                          ValueType v2 ) const
+    {
+        const typename vigra::NumericTraits<AlphaType>::RealPromote fAlpha(
+            vigra::NumericTraits<AlphaType>::toRealPromote(alpha));
+        return fAlpha*v1 + (vigra::NumericTraits<AlphaType>::one()-fAlpha)*v2;
+    }
+};
+
+/** Functor template, to calculate alpha blending between two
+    values. Integer case.
+
+    @tpl polarity
+    When true, 0 means fully transparent, and 1 fully opaque. And vice
+    versa.
+ */
+template< typename ValueType,
+          typename AlphaType,
+          bool     polarity > struct IntegerBlendFunctor;
+template< typename ValueType,
+          typename AlphaType > struct IntegerBlendFunctor<ValueType,AlphaType,true>
+  : public TernaryFunctorBase<AlphaType,ValueType,ValueType,ValueType>
+{
+    ValueType operator()( AlphaType alpha,
+                          ValueType v1,
+                          ValueType v2 ) const
+    {
+        return (vigra::NumericTraits<AlphaType>::toPromote(
+                    vigra::NumericTraits<AlphaType>::max()-alpha)*v1 + alpha*v2) /
+            vigra::NumericTraits<AlphaType>::max();
+    }
+};
+template< typename ValueType,
+          typename AlphaType > struct IntegerBlendFunctor<ValueType,AlphaType,false>
+  : public TernaryFunctorBase<AlphaType,ValueType,ValueType,ValueType>
+{
+    ValueType operator()( AlphaType alpha,
+                          ValueType v1,
+                          ValueType v2 ) const
+    {
+        return (alpha*v1 +
+                vigra::NumericTraits<AlphaType>::toPromote(
+                    vigra::NumericTraits<AlphaType>::max()-alpha)*v2) /
+            vigra::NumericTraits<AlphaType>::max();
+    }
+};
+
+//-----------------------------------------------------------------------------
+
+template< typename ColorType > struct ColorTraits
+{
+    /// Metafunction to select blend functor from color and alpha type
+    template< typename AlphaType, bool polarity > struct blend_functor : public
+        ifScalarIntegral< AlphaType,
+                          IntegerBlendFunctor< ColorType, AlphaType, polarity >,
+                          BlendFunctor< ColorType, AlphaType, polarity > > {};
+
+    /// @return number of color channels
+    static int numChannels() { return 1; }
+
+    /// Type of a color component (i.e. the type of an individual channel)
+    typedef ColorType component_type;
+
+    /// Calculate normalized distance between color c1 and c2
+    static inline vigra::NormTraits<ColorType> distance( ColorType c1,
+                                                         ColorType c2 )
+    {
+        return vigra::norm(c1 - c2);
+    }
+
+    static inline component_type toGreyscale( ColorType c )
+    {
+        return c;
+    }
+
+    static inline ColorType fromGreyscale( component_type c )
+    {
+        return c;
+    }
+};
+
+} // namespace basebmp
+
+#endif /* INCLUDED_BASEBMP_COLORTRAITS_HXX */