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+/* ============================================================
+ *
+ * This file is a part of digiKam project
+ * http://www.digikam.org
+ *
+ * Date        : 2006-03-02
+ * Description : DColor methods for composing
+ *
+ * Copyright (C) 2006-2007 by Marcel Wiesweg <marcel.wiesweg@gmx.de>
+ *
+ * This program is free software; you can redistribute it
+ * and/or modify it under the terms of the GNU General
+ * Public License as published by the Free Software Foundation;
+ * either version 2, or (at your option)
+ * any later version.
+ * 
+ * This program 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 General Public License for more details.
+ *
+ * ============================================================ */
+
+#ifndef DCOLORCOMPOSER_H
+#define DCOLORCOMPOSER_H
+
+// Local includes.
+
+#include "dcolor.h"
+#include "digikam_export.h"
+
+namespace Digikam
+{
+
+class DIGIKAM_EXPORT DColorComposer
+{
+public:
+    /** The available rules to combine src and destination color.
+
+        For the Porter-Duff rules, the formula is
+            component = (source * fs + destination * fd)
+        where
+            fs, fd according to the following table with
+            sa = source alpha,
+            da = destination alpha:
+
+            None          fs: sa      fd: 1.0-sa
+            Clear         fs: 0.0     fd: 0.0
+            Src           fs: 1.0     fd: 0.0
+            Src Over      fs: 1.0     fd: 1.0-sa
+            Dst Over      fs: 1.0-da  fd: 1.0
+            Src In        fs: da      fd: 0.0
+            Dst In        fs: 0.0     fd: sa
+            Src Out       fs: 1.0-da  fd: 0.0
+            Dst Out       fs: 0.0     fd: 1.0-sa
+
+            Src Atop      fs: da      fd: 1.0-sa
+            Dst Atop      fs: 1.0-da  fd: sa
+            Xor           fs: 1.0-da  fd: 1.0-sa
+
+            None is the default, classical blending mode, a "Src over" simplification:
+             Blend non-premultiplied RGBA data "src over" a fully opaque background.
+            Src is the painter's algorithm.
+            All other operations require premultiplied colors.
+            The documentation of java.awt.AlphaComposite (Java 1.5)
+            provides a good introduction and documentation on Porter Duff.
+     */
+
+    enum CompositingOperation
+    {
+        PorterDuffNone,
+        PorterDuffClear,
+        PorterDuffSrc,
+        PorterDuffSrcOver,
+        PorterDuffDstOver,
+        PorterDuffSrcIn,
+        PorterDuffDstIn,
+        PorterDuffSrcOut,
+        PorterDuffDstOut,
+        PorterDuffSrcAtop,
+        PorterDuffDstAtop,
+        PorterDuffXor
+    };
+
+    enum MultiplicationFlags
+    {
+        NoMultiplication = 0x00,
+        PremultiplySrc   = 0x01,
+        PremultiplyDst   = 0x02,
+        DemultiplyDst    = 0x04,
+
+        MultiplicationFlagsDImg = PremultiplySrc | PremultiplyDst | DemultiplyDst,
+        MultiplicationFlagsPremultipliedColorOnDImg = PremultiplyDst | DemultiplyDst
+    };
+
+    /**
+        Retrieve a DColorComposer object for one of the predefined rules.
+        The object needs to be deleted by the caller.
+    */
+    static DColorComposer *getComposer(CompositingOperation rule);
+
+    /**
+        Carry out the actual composition process.
+        Src and Dest are composed and the result is written to dest.
+        No pre-/demultiplication is done by this method, use the other overloaded
+        methods, which call this method, if you need  pre- or demultiplication
+        (you need it if any of the colors are read from or written to a DImg).
+
+        If you just pass the object to a DImg method, you do not need to call this.
+        Call this function if you want to compose two colors.
+        Implement this function if you create a custom DColorComposer.
+
+        The bit depth of source and destination color must be identical.
+    */
+    virtual void compose(DColor &dest, DColor src) = 0;
+
+    /**
+        Compose the two colors by calling compose(dest, src).
+        Pre- and demultiplication operations are done as specified.
+        For PorterDuff operations except PorterDuffNone, you need
+
+        - PremultiplySrc    if src is not premultiplied (read from a DImg)
+        - PremultiplyDst    if dst is not premultiplied (read from a DImg)
+        - DemultiplyDst     if dst will be written to non-premultiplied data (a DImg)
+    */
+    virtual void compose(DColor &dest, DColor src, MultiplicationFlags multiplicationFlags);
+    
+    virtual ~DColorComposer(){};
+};
+
+}  // namespace Digikam
+
+#endif  // DCOLORCOMPOSER_H