/* ============================================================
 *
 * 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
