/* -*-c++-*- OpenSceneGraph - Copyright (C) 1998-2006 Robert Osfield
 *
 * This library is open source and may be redistributed and/or modified under
 * the terms of the OpenSceneGraph Public License (OSGPL) version 0.0 or
 * (at your option) any later version.  The full license is in LICENSE file
 * included with this distribution, and on the openscenegraph.org website.
 *
 * This library 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
 * OpenSceneGraph Public License for more details.
*/

#include <float.h>
#include <string.h>

#include <osg/Math>
#include <osg/Notify>
#include <osg/ImageUtils>
#include <osg/Texture>

namespace osg
{

struct FindRangeOperator : public CastAndScaleToFloatOperation
{
    FindRangeOperator():
        _rmin(FLT_MAX),
        _rmax(-FLT_MAX),
        _gmin(FLT_MAX),
        _gmax(-FLT_MAX),
        _bmin(FLT_MAX),
        _bmax(-FLT_MAX),
        _amin(FLT_MAX),
        _amax(-FLT_MAX) {}

    float _rmin, _rmax, _gmin, _gmax, _bmin, _bmax, _amin, _amax;

    inline void luminance(float l) { rgba(l,l,l,l); }
    inline void alpha(float a) { rgba(1.0f,1.0f,1.0f,a); }
    inline void luminance_alpha(float l,float a) { rgba(l,l,l,a); }
    inline void rgb(float r,float g,float b) { rgba(r,g,b,1.0f);  }
    inline void rgba(float r,float g,float b,float a)
    {
        _rmin = osg::minimum(r,_rmin);
        _rmax = osg::maximum(r,_rmax);
        _gmin = osg::minimum(g,_gmin);
        _gmax = osg::maximum(g,_gmax);
        _bmin = osg::minimum(b,_bmin);
        _bmax = osg::maximum(b,_bmax);
        _amin = osg::minimum(a,_amin);
        _amax = osg::maximum(a,_amax);
    }



};

struct OffsetAndScaleOperator
{
    OffsetAndScaleOperator(const osg::Vec4& offset, const osg::Vec4& scale):
        _offset(offset),
        _scale(scale) {}

    osg::Vec4 _offset;
    osg::Vec4 _scale;

    inline void luminance(float& l) const { l= _offset.r() + l*_scale.r(); }
    inline void alpha(float& a) const { a = _offset.a() + a*_scale.a(); }
    inline void luminance_alpha(float& l,float& a) const
    {
        l= _offset.r() + l*_scale.r();
        a = _offset.a() + a*_scale.a();
    }
    inline void rgb(float& r,float& g,float& b) const
    {
        r = _offset.r() + r*_scale.r();
        g = _offset.g() + g*_scale.g();
        b = _offset.b() + b*_scale.b();
    }
    inline void rgba(float& r,float& g,float& b,float& a) const
    {
        r = _offset.r() + r*_scale.r();
        g = _offset.g() + g*_scale.g();
        b = _offset.b() + b*_scale.b();
        a = _offset.a() + a*_scale.a();
    }
};

bool computeMinMax(const osg::Image* image, osg::Vec4& minValue, osg::Vec4& maxValue)
{
    if (!image) return false;

    osg::FindRangeOperator rangeOp;
    readImage(image, rangeOp);
    minValue.r() = rangeOp._rmin;
    minValue.g() = rangeOp._gmin;
    minValue.b() = rangeOp._bmin;
    minValue.a() = rangeOp._amin;

    maxValue.r() = rangeOp._rmax;
    maxValue.g() = rangeOp._gmax;
    maxValue.b() = rangeOp._bmax;
    maxValue.a() = rangeOp._amax;

    return minValue.r()<=maxValue.r() &&
           minValue.g()<=maxValue.g() &&
           minValue.b()<=maxValue.b() &&
           minValue.a()<=maxValue.a();
}

bool offsetAndScaleImage(osg::Image* image, const osg::Vec4& offset, const osg::Vec4& scale)
{
    if (!image) return false;

    modifyImage(image,OffsetAndScaleOperator(offset, scale));

    return true;
}

template<typename SRC, typename DEST>
void _copyRowAndScale(const SRC* src, DEST* dest, int num, float scale)
{
    if (scale==1.0)
    {
        for(int i=0; i<num; ++i)
        {
            *dest = DEST(*src);
            ++dest; ++src;
        }
    }
    else
    {
        for(int i=0; i<num; ++i)
        {
            *dest = DEST(float(*src)*scale);
            ++dest; ++src;
        }
    }
}

template<typename DEST>
void _copyRowAndScale(const unsigned char* src, GLenum srcDataType, DEST* dest, int num, float scale)
{
    switch(srcDataType)
    {
        case(GL_BYTE):              _copyRowAndScale((char*)src, dest, num, scale); break;
        case(GL_UNSIGNED_BYTE):     _copyRowAndScale((unsigned char*)src, dest, num, scale); break;
        case(GL_SHORT):             _copyRowAndScale((short*)src, dest, num, scale); break;
        case(GL_UNSIGNED_SHORT):    _copyRowAndScale((unsigned short*)src, dest, num, scale); break;
        case(GL_INT):               _copyRowAndScale((int*)src, dest, num, scale); break;
        case(GL_UNSIGNED_INT):      _copyRowAndScale((unsigned int*)src, dest, num, scale); break;
        case(GL_FLOAT):             _copyRowAndScale((float*)src, dest, num, scale); break;
    }
}

void _copyRowAndScale(const unsigned char* src, GLenum srcDataType, unsigned char* dest, GLenum dstDataType, int num, float scale)
{
    switch(dstDataType)
    {
        case(GL_BYTE):              _copyRowAndScale(src, srcDataType, (char*)dest, num, scale); break;
        case(GL_UNSIGNED_BYTE):     _copyRowAndScale(src, srcDataType, (unsigned char*)dest, num, scale); break;
        case(GL_SHORT):             _copyRowAndScale(src, srcDataType, (short*)dest, num, scale); break;
        case(GL_UNSIGNED_SHORT):    _copyRowAndScale(src, srcDataType, (unsigned short*)dest, num, scale); break;
        case(GL_INT):               _copyRowAndScale(src, srcDataType, (int*)dest, num, scale); break;
        case(GL_UNSIGNED_INT):      _copyRowAndScale(src, srcDataType, (unsigned int*)dest, num, scale); break;
        case(GL_FLOAT):             _copyRowAndScale(src, srcDataType, (float*)dest, num, scale); break;
    }
}

struct RecordRowOperator : public CastAndScaleToFloatOperation
{
    RecordRowOperator(unsigned int num):_colours(num),_pos(0) {}

    mutable std::vector<osg::Vec4>  _colours;
    mutable unsigned int            _pos;

    inline void luminance(float l) const { rgba(l,l,l,1.0f); }
    inline void alpha(float a) const { rgba(1.0f,1.0f,1.0f,a); }
    inline void luminance_alpha(float l,float a) const { rgba(l,l,l,a);  }
    inline void rgb(float r,float g,float b) const { rgba(r,g,b,1.0f); }
    inline void rgba(float r,float g,float b,float a) const { _colours[_pos++].set(r,g,b,a); }
};

struct WriteRowOperator
{
    WriteRowOperator():_pos(0) {}
    WriteRowOperator(unsigned int num):_colours(num),_pos(0) {}

    std::vector<osg::Vec4>  _colours;
    mutable unsigned int    _pos;

    inline void luminance(float& l) const { l = _colours[_pos++].r(); }
    inline void alpha(float& a) const { a = _colours[_pos++].a(); }
    inline void luminance_alpha(float& l,float& a) const { l = _colours[_pos].r(); a = _colours[_pos++].a(); }
    inline void rgb(float& r,float& g,float& b) const { r = _colours[_pos].r(); g = _colours[_pos].g(); b = _colours[_pos].b(); }
    inline void rgba(float& r,float& g,float& b,float& a) const {  r = _colours[_pos].r(); g = _colours[_pos].g(); b = _colours[_pos].b(); a = _colours[_pos++].a(); }
};

bool copyImage(const osg::Image* srcImage, int src_s, int src_t, int src_r, int width, int height, int depth,
               osg::Image* destImage, int dest_s, int dest_t, int dest_r, bool doRescale)
{
    if ((dest_s+width) > (destImage->s()))
    {
        OSG_NOTICE<<"copyImage("<<srcImage<<", "<<src_s<<", "<< src_t<<", "<<src_r<<", "<<width<<", "<<height<<", "<<depth<<std::endl;
        OSG_NOTICE<<"          "<<destImage<<", "<<dest_s<<", "<< dest_t<<", "<<dest_r<<", "<<doRescale<<")"<<std::endl;
        OSG_NOTICE<<"   input width too large."<<std::endl;
        return false;
    }

    if ((dest_t+height) > (destImage->t()))
    {
        OSG_NOTICE<<"copyImage("<<srcImage<<", "<<src_s<<", "<< src_t<<", "<<src_r<<", "<<width<<", "<<height<<", "<<depth<<std::endl;
        OSG_NOTICE<<"          "<<destImage<<", "<<dest_s<<", "<< dest_t<<", "<<dest_r<<", "<<doRescale<<")"<<std::endl;
        OSG_NOTICE<<"   input height too large."<<std::endl;
        return false;
    }

    if ((dest_r+depth) > (destImage->r()))
    {
        OSG_NOTICE<<"copyImage("<<srcImage<<", "<<src_s<<", "<< src_t<<", "<<src_r<<", "<<width<<", "<<height<<", "<<depth<<std::endl;
        OSG_NOTICE<<"          "<<destImage<<", "<<dest_s<<", "<< dest_t<<", "<<dest_r<<", "<<doRescale<<")"<<std::endl;
        OSG_NOTICE<<"   input depth too large."<<std::endl;
        return false;
    }

    float scale = 1.0f;
    if (doRescale && srcImage->getDataType() != destImage->getDataType())
    {
        switch(srcImage->getDataType())
        {
            case(GL_BYTE):              scale = 1.0f/128.0f ; break;
            case(GL_UNSIGNED_BYTE):     scale = 1.0f/255.0f; break;
            case(GL_SHORT):             scale = 1.0f/32768.0f; break;
            case(GL_UNSIGNED_SHORT):    scale = 1.0f/65535.0f; break;
            case(GL_INT):               scale = 1.0f/2147483648.0f; break;
            case(GL_UNSIGNED_INT):      scale = 1.0f/4294967295.0f; break;
            case(GL_FLOAT):             scale = 1.0f; break;
        }
        switch(destImage->getDataType())
        {
            case(GL_BYTE):              scale *= 128.0f ; break;
            case(GL_UNSIGNED_BYTE):     scale *= 255.0f; break;
            case(GL_SHORT):             scale *= 32768.0f; break;
            case(GL_UNSIGNED_SHORT):    scale *= 65535.0f; break;
            case(GL_INT):               scale *= 2147483648.0f; break;
            case(GL_UNSIGNED_INT):      scale *= 4294967295.0f; break;
            case(GL_FLOAT):             scale *= 1.0f; break;
        }
    }

    if (srcImage->getPixelFormat() == destImage->getPixelFormat())
    {
        //OSG_NOTICE<<"copyImage("<<srcImage<<", "<<src_s<<", "<< src_t<<", "<<src_r<<", "<<width<<", "<<height<<", "<<depth<<std::endl;
        //OSG_NOTICE<<"          "<<destImage<<", "<<dest_s<<", "<< dest_t<<", "<<dest_r<<", "<<doRescale<<")"<<std::endl;

        if (srcImage->getDataType() == destImage->getDataType() && !doRescale)
        {
            //OSG_NOTICE<<"   Compatible pixelFormat and dataType."<<std::endl;
            for(int slice = 0; slice<depth; ++slice)
            {
                for(int row = 0; row<height; ++row)
                {
                    const unsigned char* srcData = srcImage->data(src_s, src_t+row, src_r+slice);
                    unsigned char* destData = destImage->data(dest_s, dest_t+row, dest_r+slice);
                    memcpy(destData, srcData, (width*destImage->getPixelSizeInBits())/8);
                }
            }
            return true;
        }
        else
        {
            //OSG_NOTICE<<"   Compatible pixelFormat and incompatible dataType."<<std::endl;
            for(int slice = 0; slice<depth; ++slice)
            {
                for(int row = 0; row<height; ++row)
                {
                    const unsigned char* srcData = srcImage->data(src_s, src_t+row, src_r+slice);
                    unsigned char* destData = destImage->data(dest_s, dest_t+row, dest_r+slice);
                    unsigned int numComponents = osg::Image::computeNumComponents(destImage->getPixelFormat());

                    _copyRowAndScale(srcData, srcImage->getDataType(), destData, destImage->getDataType(), (width*numComponents), scale);
                }
            }

            return true;
        }
    }
    else
    {
        //OSG_NOTICE<<"copyImage("<<srcImage<<", "<<src_s<<", "<< src_t<<", "<<src_r<<", "<<width<<", "<<height<<", "<<depth<<std::endl;
        //OSG_NOTICE<<"          "<<destImage<<", "<<dest_s<<", "<< dest_t<<", "<<dest_r<<", "<<doRescale<<")"<<std::endl;

        RecordRowOperator readOp(width);
        WriteRowOperator writeOp;

        for(int slice = 0; slice<depth; ++slice)
        {
            for(int row = 0; row<height; ++row)
            {

                // reset the indices to beginning
                readOp._pos = 0;
                writeOp._pos = 0;

                // read the pixels into readOp's _colour array
                readRow(width, srcImage->getPixelFormat(), srcImage->getDataType(), srcImage->data(src_s,src_t+row,src_r+slice), readOp);

                // pass readOp's _colour array contents over to writeOp (note this is just a pointer swap).
                writeOp._colours.swap(readOp._colours);

                modifyRow(width, destImage->getPixelFormat(), destImage->getDataType(), destImage->data(dest_s, dest_t+row,dest_r+slice), writeOp);

                // return readOp's _colour array contents back to its rightful owner.
                writeOp._colours.swap(readOp._colours);
            }
        }

        return true;
    }

}


struct SetToColourOperator
{
    SetToColourOperator(const osg::Vec4& colour):
        _colour(colour) {}

    inline void luminance(float& l) const { l = (_colour.r()+_colour.g()+_colour.b())*0.333333; }
    inline void alpha(float& a) const { a = _colour.a(); }
    inline void luminance_alpha(float& l,float& a) const { l = (_colour.r()+_colour.g()+_colour.b())*0.333333; a = _colour.a(); }
    inline void rgb(float& r,float& g,float& b) const { r = _colour.r(); g = _colour.g(); b = _colour.b(); }
    inline void rgba(float& r,float& g,float& b,float& a) const { r = _colour.r(); g = _colour.g(); b = _colour.b(); a = _colour.a(); }

    osg::Vec4 _colour;
};

bool clearImageToColor(osg::Image* image, const osg::Vec4& colour)
{
    if (!image) return false;

    modifyImage(image, SetToColourOperator(colour));

    return true;
}

/** Search through the list of Images and find the maximum number of components used amoung the images.*/
unsigned int maximimNumOfComponents(const ImageList& imageList)
{
    unsigned int max_components = 0;
    for(osg::ImageList::const_iterator itr=imageList.begin();
        itr!=imageList.end();
        ++itr)
    {
        osg::Image* image = itr->get();
        GLenum pixelFormat = image->getPixelFormat();
        if (pixelFormat==GL_ALPHA ||
            pixelFormat==GL_INTENSITY ||
            pixelFormat==GL_LUMINANCE ||
            pixelFormat==GL_LUMINANCE_ALPHA ||
            pixelFormat==GL_RGB ||
            pixelFormat==GL_RGBA ||
            pixelFormat==GL_BGR ||
            pixelFormat==GL_BGRA)
        {
            max_components = maximum(Image::computeNumComponents(pixelFormat), max_components);
        }
    }
    return max_components;
}

osg::Image* createImage3D(const ImageList& imageList,
                          GLenum desiredPixelFormat,
                          int s_maximumImageSize,
                          int t_maximumImageSize,
                          int r_maximumImageSize,
                          bool resizeToPowerOfTwo)
{
    OSG_INFO<<"createImage3D(..)"<<std::endl;
    int max_s = 0;
    int max_t = 0;
    int total_r = 0;
    for(osg::ImageList::const_iterator itr=imageList.begin();
        itr!=imageList.end();
        ++itr)
    {
        osg::Image* image = itr->get();
        GLenum pixelFormat = image->getPixelFormat();
        if (pixelFormat==GL_ALPHA ||
            pixelFormat==GL_INTENSITY ||
            pixelFormat==GL_LUMINANCE ||
            pixelFormat==GL_LUMINANCE_ALPHA ||
            pixelFormat==GL_RGB ||
            pixelFormat==GL_RGBA ||
            pixelFormat==GL_BGR ||
            pixelFormat==GL_BGRA)
        {
            max_s = maximum(image->s(), max_s);
            max_t = maximum(image->t(), max_t);
            total_r += image->r();
        }
        else
        {
            OSG_INFO<<"Image "<<image->getFileName()<<" has unsuitable pixel format 0x"<< std::hex<< pixelFormat << std::dec << std::endl;
        }
    }

    //bool remapRGBtoLuminance;
    //bool remapRGBtoRGBA;

    if (desiredPixelFormat==0)
    {
        unsigned int max_components = maximimNumOfComponents(imageList);
        switch(max_components)
        {
        case(1):
            OSG_INFO<<"desiredPixelFormat = GL_LUMINANCE" << std::endl;
            desiredPixelFormat = GL_LUMINANCE;
            break;
        case(2):
            OSG_INFO<<"desiredPixelFormat = GL_LUMINANCE_ALPHA" << std::endl;
            desiredPixelFormat = GL_LUMINANCE_ALPHA;
            break;
        case(3):
            OSG_INFO<<"desiredPixelFormat = GL_RGB" << std::endl;
            desiredPixelFormat = GL_RGB;
            break;
        case(4):
            OSG_INFO<<"desiredPixelFormat = GL_RGBA" << std::endl;
            desiredPixelFormat = GL_RGBA;
            break;
        }
    }
    if (desiredPixelFormat==0) return 0;

    // compute nearest powers of two for each axis.

    int size_s = 1;
    int size_t = 1;
    int size_r = 1;

    if (resizeToPowerOfTwo)
    {
        while(size_s<max_s && size_s<s_maximumImageSize) size_s*=2;
        while(size_t<max_t && size_t<t_maximumImageSize) size_t*=2;
        while(size_r<total_r && size_r<r_maximumImageSize) size_r*=2;
    }
    else
    {
        size_s = max_s;
        size_t = max_t;
        size_r = total_r;
    }

    // now allocate the 3d texture;
    osg::ref_ptr<osg::Image> image_3d = new osg::Image;
    image_3d->allocateImage(size_s,size_t,size_r,
                            desiredPixelFormat,GL_UNSIGNED_BYTE);

    unsigned int r_offset = (total_r<size_r) ? (size_r-total_r)/2 : 0;

    int curr_dest_r = r_offset;

    // copy across the values from the source images into the image_3d.
    for(osg::ImageList::const_iterator itr=imageList.begin();
        itr!=imageList.end();
        ++itr)
    {
        osg::Image* image = itr->get();
        GLenum pixelFormat = image->getPixelFormat();
        if (pixelFormat==GL_ALPHA ||
            pixelFormat==GL_LUMINANCE ||
            pixelFormat==GL_INTENSITY ||
            pixelFormat==GL_LUMINANCE_ALPHA ||
            pixelFormat==GL_RGB ||
            pixelFormat==GL_RGBA ||
            pixelFormat==GL_BGR ||
            pixelFormat==GL_BGRA)
        {

            int num_s = minimum(image->s(), image_3d->s());
            int num_t = minimum(image->t(), image_3d->t());
            int num_r = minimum(image->r(), (image_3d->r() - curr_dest_r));

            unsigned int s_offset_dest = (image->s()<size_s) ? (size_s - image->s())/2 : 0;
            unsigned int t_offset_dest = (image->t()<size_t) ? (size_t - image->t())/2 : 0;

            copyImage(image, 0, 0, 0, num_s, num_t, num_r,
                      image_3d.get(), s_offset_dest, t_offset_dest, curr_dest_r, false);

            curr_dest_r += num_r;
        }
    }

    return image_3d.release();
}

struct ModulateAlphaByLuminanceOperator
{
    ModulateAlphaByLuminanceOperator() {}

    inline void luminance(float&) const {}
    inline void alpha(float&) const {}
    inline void luminance_alpha(float& l,float& a) const { a*= l; }
    inline void rgb(float&,float&,float&) const {}
    inline void rgba(float& r,float& g,float& b,float& a) const { float l = (r+g+b)*0.3333333; a *= l;}
};

osg::Image* createImage3DWithAlpha(const ImageList& imageList,
            int s_maximumImageSize,
            int t_maximumImageSize,
            int r_maximumImageSize,
            bool resizeToPowerOfTwo)
{
    GLenum desiredPixelFormat = 0;
    bool modulateAlphaByLuminance = false;

    unsigned int maxNumComponents = maximimNumOfComponents(imageList);
    if (maxNumComponents==3)
    {
        desiredPixelFormat = GL_RGBA;
        modulateAlphaByLuminance = true;
    }

    osg::ref_ptr<osg::Image> image = createImage3D(imageList,
                                        desiredPixelFormat,
                                        s_maximumImageSize,
                                        t_maximumImageSize,
                                        r_maximumImageSize,
                                        resizeToPowerOfTwo);
    if (image.valid())
    {
        if (modulateAlphaByLuminance)
        {
            modifyImage(image.get(), ModulateAlphaByLuminanceOperator());
        }
        return image.release();
    }
    else
    {
        return 0;
    }
}


static void fillSpotLightImage(unsigned char* ptr, const osg::Vec4& centerColour, const osg::Vec4& backgroudColour, unsigned int size, float power)
{
    if (size==1)
    {
        float r = 0.5f;
        osg::Vec4 color = centerColour*r+backgroudColour*(1.0f-r);
        *ptr++ = (unsigned char)((color[0])*255.0f);
        *ptr++ = (unsigned char)((color[1])*255.0f);
        *ptr++ = (unsigned char)((color[2])*255.0f);
        *ptr++ = (unsigned char)((color[3])*255.0f);
        return;
    }

    float mid = (float(size)-1.0f)*0.5f;
    float div = 2.0f/float(size);
    for(unsigned int r=0;r<size;++r)
    {
        //unsigned char* ptr = image->data(0,r,0);
        for(unsigned int c=0;c<size;++c)
        {
            float dx = (float(c) - mid)*div;
            float dy = (float(r) - mid)*div;
            float r = powf(1.0f-sqrtf(dx*dx+dy*dy),power);
            if (r<0.0f) r=0.0f;
            osg::Vec4 color = centerColour*r+backgroudColour*(1.0f-r);
            *ptr++ = (unsigned char)((color[0])*255.0f);
            *ptr++ = (unsigned char)((color[1])*255.0f);
            *ptr++ = (unsigned char)((color[2])*255.0f);
            *ptr++ = (unsigned char)((color[3])*255.0f);
        }
    }
}

osg::Image* createSpotLightImage(const osg::Vec4& centerColour, const osg::Vec4& backgroudColour, unsigned int size, float power)
{

#if 0
    osg::Image* image = new osg::Image;
    unsigned char* ptr = image->data(0,0,0);
    fillSpotLightImage(ptr, centerColour, backgroudColour, size, power);

    return image;
#else
    osg::Image* image = new osg::Image;
    osg::Image::MipmapDataType mipmapData;
    unsigned int s = size;
    unsigned int totalSize = 0;
    unsigned i;
    for(i=0; s>0; s>>=1, ++i)
    {
        if (i>0) mipmapData.push_back(totalSize);
        totalSize += s*s*4;
    }

    unsigned char* ptr = new unsigned char[totalSize];
    image->setImage(size, size, size, GL_RGBA, GL_RGBA, GL_UNSIGNED_BYTE, ptr, osg::Image::USE_NEW_DELETE,1);

    image->setMipmapLevels(mipmapData);

    s = size;
    for(i=0; s>0; s>>=1, ++i)
    {
        fillSpotLightImage(ptr, centerColour, backgroudColour, s, power);
        ptr += s*s*4;
    }

    return image;
#endif
}



struct ModulateAlphaByColorOperator
{
    ModulateAlphaByColorOperator(const osg::Vec4& colour):_colour(colour) { _lum = _colour.length(); }

    osg::Vec4 _colour;
    float _lum;

    inline void luminance(float&) const {}
    inline void alpha(float&) const {}
    inline void luminance_alpha(float& l,float& a) const { a*= l*_lum; }
    inline void rgb(float&,float&,float&) const {}
    inline void rgba(float& r,float& g,float& b,float& a) const { a = (r*_colour.r()+g*_colour.g()+b*_colour.b()+a*_colour.a()); }
};

struct ReplaceAlphaWithLuminanceOperator
{
    ReplaceAlphaWithLuminanceOperator() {}

    inline void luminance(float&) const {}
    inline void alpha(float&) const {}
    inline void luminance_alpha(float& l,float& a) const { a = l; }
    inline void rgb(float&,float&,float&) const { }
    inline void rgba(float& r,float& g,float& b,float& a) const { float l = (r+g+b)*0.3333333; a = l; }
};

osg::Image* colorSpaceConversion(ColorSpaceOperation op, osg::Image* image, const osg::Vec4& colour)
{
    GLenum requiredPixelFormat = image->getPixelFormat();
    switch(op)
    {
        case (MODULATE_ALPHA_BY_LUMINANCE):
        case (MODULATE_ALPHA_BY_COLOR):
        case (REPLACE_ALPHA_WITH_LUMINANCE):
            if (image->getPixelFormat()==GL_RGB || image->getPixelFormat()==GL_BGR) requiredPixelFormat = GL_RGBA;
            break;
        case (REPLACE_RGB_WITH_LUMINANCE):
            if (image->getPixelFormat()==GL_RGB || image->getPixelFormat()==GL_BGR) requiredPixelFormat = GL_LUMINANCE;
            break;
        default:
            break;
    }

    if (requiredPixelFormat!=image->getPixelFormat())
    {
        osg::Image* newImage = new osg::Image;
        newImage->allocateImage(image->s(), image->t(), image->r(), requiredPixelFormat, image->getDataType());
        osg::copyImage(image, 0, 0, 0, image->s(), image->t(), image->r(),
                    newImage, 0, 0, 0, false);

        image = newImage;
    }

    switch(op)
    {
        case (MODULATE_ALPHA_BY_LUMINANCE):
        {
            OSG_NOTICE<<"doing conversion MODULATE_ALPHA_BY_LUMINANCE"<<std::endl;
            osg::modifyImage(image, ModulateAlphaByLuminanceOperator());
            return image;
        }
        case (MODULATE_ALPHA_BY_COLOR):
        {
            OSG_NOTICE<<"doing conversion MODULATE_ALPHA_BY_COLOUR"<<std::endl;
            osg::modifyImage(image, ModulateAlphaByColorOperator(colour));
            return image;
        }
        case (REPLACE_ALPHA_WITH_LUMINANCE):
        {
            OSG_NOTICE<<"doing conversion REPLACE_ALPHA_WITH_LUMINANCE"<<std::endl;
            osg::modifyImage(image, ReplaceAlphaWithLuminanceOperator());
            return image;
        }
        case (REPLACE_RGB_WITH_LUMINANCE):
        {
            OSG_NOTICE<<"doing conversion REPLACE_RGB_WITH_LUMINANCE"<<std::endl;
            // no work here required to be done as it'll already be done by copyImage above.
            return image;
        }
        default:
            return image;
    }
}



}

