Dear Robert,

Given no replies to my recent "does anybody use the DDS writer" query, I was
emboldened to submit this very small patch. The bitmasks for RGBA and RGB
have been modified in the writer portion of the code (line 765 onwards).
This is now consistent with what the DDS plugin reads. In terms of testing,
note that many 3rd party applications erroneously ignore the bitmasks in the
file, and assume a BGRA order.

This is based on the 2.1.1 release, although I don't think it's changed
since then.

Hope that helps,

David
/**********************************************************************
*
*    FILE:            ReaderWriterdds.cpp
*
*    DESCRIPTION:    Class for reading a DDS file into an osg::Image.
*
*                    Example on reading a DDS file code can be found at:
*                    http://developer.nvidia.com/docs/IO/1327/ATT/
*                    ARB_texture_compression.pdf
*                    Author: Sebastien Domine, NVIDIA Corporation
*
*    CREATED BY:        Rune Schmidt Jensen, [EMAIL PROTECTED]
*
*    HISTORY:        Created   31.03.2003
*             Modified  13.05.2004
*                by George Tarantilis, [EMAIL PROTECTED]
*
**********************************************************************/

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

#include <osgDB/Registry>
#include <osgDB/FileNameUtils>
#include <osgDB/FileUtils>

#include <iomanip>
#include <stdio.h>


// NOTICE ON WIN32:
// typedef DWORD unsigned long;
// sizeof(DWORD) = 4

typedef unsigned int UI32;
typedef int I32;

struct  DDCOLORKEY
{
    DDCOLORKEY():
        dwColorSpaceLowValue(0),
        dwColorSpaceHighValue(0) {}
        
    UI32    dwColorSpaceLowValue;
    UI32    dwColorSpaceHighValue;
};

struct DDPIXELFORMAT
{

    DDPIXELFORMAT():
        dwSize(0),
        dwFlags(0),
        dwFourCC(0),
        dwRGBBitCount(0),
        dwRBitMask(0),
        dwGBitMask(0),
        dwBBitMask(0),
        dwRGBAlphaBitMask(0) {}
        

    UI32    dwSize;
    UI32    dwFlags;
    UI32    dwFourCC;
    union
    {
        UI32    dwRGBBitCount;
        UI32    dwYUVBitCount;
        UI32    dwZBufferBitDepth;
        UI32    dwAlphaBitDepth;
        UI32    dwLuminanceBitDepth;
    };
    union
    {
        UI32    dwRBitMask;
        UI32    dwYBitMask;
    };
    union
    {
        UI32    dwGBitMask;
        UI32    dwUBitMask;
    };
    union
    {
        UI32    dwBBitMask;
        UI32    dwVBitMask;
    };
    union
    {
        UI32    dwRGBAlphaBitMask;
        UI32    dwYUVAlphaBitMask;
        UI32    dwRGBZBitMask;
        UI32    dwYUVZBitMask;
    };
};

struct  DDSCAPS2
{
     DDSCAPS2():
        dwCaps(0),
        dwCaps2(0),
        dwCaps3(0),
        dwCaps4(0) {}

    UI32       dwCaps;
    UI32       dwCaps2;
    UI32       dwCaps3;
    union
    {
        UI32       dwCaps4;
        UI32       dwVolumeDepth;
    };
};

struct DDSURFACEDESC2
{
    DDSURFACEDESC2():
        dwSize(0),
        dwFlags(0),
        dwHeight(0),
        dwWidth(0), 
        lPitch(0),
        dwBackBufferCount(0),
        dwMipMapCount(0),
        dwAlphaBitDepth(0),
        dwReserved(0),     
        lpSurface(0),      
        dwTextureStage(0) {}      
        

    UI32         dwSize;
    UI32         dwFlags;
    UI32         dwHeight;
    UI32         dwWidth; 
    union                          
    {
        I32              lPitch;
        UI32     dwLinearSize;
    };
    union
    {
        UI32      dwBackBufferCount;
        UI32      dwDepth;      
    };
    union
    {
        UI32     dwMipMapCount;
        UI32     dwRefreshRate;
    };
    UI32         dwAlphaBitDepth;
    UI32         dwReserved;     
    UI32        lpSurface;         //Fred Marmond: removed from pointer type to UI32 for 64bits compatibility. it is unused data 
    DDCOLORKEY    ddckCKDestOverlay;      
    DDCOLORKEY    ddckCKDestBlt;           
    DDCOLORKEY    ddckCKSrcOverlay;        
    DDCOLORKEY    ddckCKSrcBlt;            
    DDPIXELFORMAT ddpfPixelFormat;         
    DDSCAPS2      ddsCaps;                 
    UI32 dwTextureStage;          
};

//
// Structure of a DXT-1 compressed texture block
// see http://msdn.microsoft.com/library/default.asp?url=/library/en-us/directx9_c/Opaque_and_1_Bit_Alpha_Textures.asp
//
struct DXT1TexelsBlock
{
    unsigned short color_0;     // colors at their
    unsigned short color_1;     // extreme
    unsigned int   texels4x4;   // interpolated colors (2 bits per texel)
};

//
// DDSURFACEDESC2 flags that mark the validity of the struct data
//
#define DDSD_CAPS               0x00000001l     // default
#define DDSD_HEIGHT             0x00000002l        // default
#define DDSD_WIDTH              0x00000004l        // default
#define DDSD_PIXELFORMAT        0x00001000l        // default
#define DDSD_PITCH              0x00000008l     // For uncompressed formats
#define DDSD_MIPMAPCOUNT        0x00020000l
#define DDSD_LINEARSIZE         0x00080000l     // For compressed formats
#define DDSD_DEPTH              0x00800000l        // Volume Textures

//
// DDPIXELFORMAT flags
//
#define DDPF_ALPHAPIXELS        0x00000001l
#define DDPF_FOURCC             0x00000004l        // Compressed formats 
#define DDPF_RGB                0x00000040l        // Uncompressed formats
#define DDPF_ALPHA              0x00000002l
#define DDPF_COMPRESSED         0x00000080l
#define DDPF_LUMINANCE          0x00020000l
#define DDPF_BUMPLUMINANCE      0x00040000l        // L,U,V
#define DDPF_BUMPDUDV           0x00080000l        // U,V

//
// DDSCAPS flags
//
#define DDSCAPS_TEXTURE         0x00001000l     // default
#define DDSCAPS_COMPLEX         0x00000008l
#define DDSCAPS_MIPMAP          0x00400000l
#define DDSCAPS2_VOLUME         0x00200000l


#ifndef MAKEFOURCC
#define MAKEFOURCC(ch0, ch1, ch2, ch3)                              \
    ((UI32)(char)(ch0) | ((UI32)(char)(ch1) << 8) |   \
    ((UI32)(char)(ch2) << 16) | ((UI32)(char)(ch3) << 24 ))
#endif //defined(MAKEFOURCC)

/*
* FOURCC codes for DX compressed-texture pixel formats
*/
#define FOURCC_DXT1  (MAKEFOURCC('D','X','T','1'))
#define FOURCC_DXT2  (MAKEFOURCC('D','X','T','2'))
#define FOURCC_DXT3  (MAKEFOURCC('D','X','T','3'))
#define FOURCC_DXT4  (MAKEFOURCC('D','X','T','4'))
#define FOURCC_DXT5  (MAKEFOURCC('D','X','T','5'))


osg::Image* ReadDDSFile(std::istream& _istream)
{

    DDSURFACEDESC2 ddsd;

    char filecode[4];
    
    _istream.read(filecode, 4);
    if (strncmp(filecode, "DDS ", 4) != 0) {
        return NULL;
    }
    // Get the surface desc.
    _istream.read((char*)(&ddsd), sizeof(ddsd));


    // Size of 2d images - 3d images don't set dwLinearSize
    //###[afarre_051904]
    /*unsigned int size = ddsd.dwMipMapCount > 1 ? ddsd.dwLinearSize * (ddsd.ddpfPixelFormat.dwFourCC==FOURCC_DXT1 ? 2: 4) : ddsd.dwLinearSize;

    if(size <= 0)
    {
        osg::notify(osg::WARN)<<"Warning:: dwLinearSize is not defined in dds file, image not loaded."<<std::endl;
        return NULL;
    }*/

    osg::ref_ptr<osg::Image> osgImage = new osg::Image();    
    
    //Check valid structure sizes
    if(ddsd.dwSize != 124 && ddsd.ddpfPixelFormat.dwSize != 32)
    {
        return NULL;
    }

    bool is3dImage = false;
    int depth = 1;

    // Check for volume image
    if( ddsd.dwDepth > 0 && (ddsd.dwFlags & DDSD_DEPTH))
    {
        is3dImage = true;
        depth = ddsd.dwDepth;
    }

    // Retreive image properties.
    int s = ddsd.dwWidth;
    int t = ddsd.dwHeight;
    int r = depth; 
    unsigned int dataType = GL_UNSIGNED_BYTE;
    unsigned int pixelFormat = 0;
    unsigned int internalFormat = 0;

    // Handle some esoteric formats
    if(ddsd.ddpfPixelFormat.dwFlags & DDPF_BUMPDUDV) 
    {
        osg::notify(osg::WARN) << "ReadDDSFile warning: DDPF_BUMPDUDV format is not supported" << std::endl;
        return NULL;
//         ddsd.ddpfPixelFormat.dwFlags =
//             DDPF_LUMINANCE + DDPF_ALPHAPIXELS;
//         // handle V8U8 as A8L8
//         // handle V16U16 as A16L16
//         // but Q8W8U8L8 as RGB?
//         // A2W10U10V10 as RGBA (dwFlags == DDPF_BUMPDUDV + DDPF_ALPHAPIXELS)
    }
    if(ddsd.ddpfPixelFormat.dwFlags & DDPF_BUMPLUMINANCE) 
    {
        osg::notify(osg::WARN) << "ReadDDSFile warning: DDPF_BUMPLUMINANCE format is not supported" << std::endl;
        return NULL;
//         ddsd.ddpfPixelFormat.dwFlags = DDPF_RGB;
//         // handle as RGB
//         // L6V5U5 -- 655 is not supported data type in GL
//         // X8L8V8U8 -- just as RGB
    }
    
    // Uncompressed formats will usually use DDPF_RGB to indicate an RGB format,
    // while compressed formats will use DDPF_FOURCC with a four-character code.
    
    bool usingAlpha = ddsd.ddpfPixelFormat.dwFlags & DDPF_ALPHAPIXELS;
    bool checkIfUsingOneBitAlpha = false;

    // Uncompressed formats.
    if(ddsd.ddpfPixelFormat.dwFlags & DDPF_RGB)
    {
        struct RGBFormat
        {
                const char*  name;
                UI32         bitCount;
                UI32         rBitMask;
                UI32         gBitMask;
                UI32         bBitMask;
                UI32         aBitMask;
                unsigned int internalFormat;
                unsigned int pixelFormat;
                unsigned int dataType;
        };

        const int UNSUPPORTED = 0;

        static const RGBFormat rgbFormats[] =            
        {
            { "R3G3B2"     ,  8,       0xe0,       0x1c,       0x03,       0x00,
              GL_RGB , GL_RGB , GL_UNSIGNED_BYTE_3_3_2 },

            { "R5G6B5"     , 16,     0xf800,     0x07e0,     0x001f,     0x0000,
              GL_RGB , GL_RGB , GL_UNSIGNED_SHORT_5_6_5 },
            { "A1R5G5B5"   , 16,     0x7c00,     0x03e0,     0x001f,     0x8000,
              GL_RGBA, GL_BGRA, GL_UNSIGNED_SHORT_1_5_5_5_REV },
            { "X1R5G5B5"   , 16,     0x7c00,     0x03e0,     0x001f,     0x0000,
              GL_RGB , GL_BGRA, GL_UNSIGNED_SHORT_1_5_5_5_REV },
            { "A4R4G4B4"   , 16,     0x0f00,     0x00f0,     0x000f,     0xf000,
              GL_RGBA, GL_BGRA, GL_UNSIGNED_SHORT_4_4_4_4_REV },
            { "X4R4G4B4"   , 16,     0x0f00,     0x00f0,     0x000f,     0x0000,
              GL_RGB , GL_BGRA, GL_UNSIGNED_SHORT_4_4_4_4_REV },
            { "A8R3G3B2"   , 16,     0x00e0,     0x001c,     0x0003,     0xff00,
              GL_RGBA, GL_BGRA, UNSUPPORTED },

            { "R8G8B8",      24,   0xff0000,   0x00ff00,   0x0000ff,   0x000000,
              GL_RGB , GL_BGR , GL_UNSIGNED_BYTE }, 

            { "A8R8G8B8",    32, 0x00ff0000, 0x0000ff00, 0x000000ff, 0xff000000,
              GL_RGBA, GL_BGRA, GL_UNSIGNED_BYTE }, 
            { "X8R8G8B8",    32, 0x00ff0000, 0x0000ff00, 0x000000ff, 0x00000000,
              GL_RGB , GL_BGRA, GL_UNSIGNED_BYTE }, 
            { "A8B8G8R8",    32, 0x000000ff, 0x0000ff00, 0x00ff0000, 0xff000000,
              GL_RGBA, GL_RGBA, GL_UNSIGNED_BYTE }, 
            { "X8B8G8R8",    32, 0x000000ff, 0x0000ff00, 0x00ff0000, 0x00000000,
              GL_RGB , GL_RGBA, GL_UNSIGNED_BYTE }, 
            { "A2R10G10B10", 32, 0x000003ff, 0x000ffc00, 0x3ff00000, 0xc0000000,
              GL_RGBA, GL_BGRA, GL_UNSIGNED_INT_2_10_10_10_REV }, 
            { "A2B10G10R10", 32, 0x3ff00000, 0x000ffc00, 0x000003ff, 0xc0000000,
              GL_RGBA, GL_RGBA, GL_UNSIGNED_INT_2_10_10_10_REV }, 
            { "G16R16",      32, 0x0000ffff, 0xffff0000, 0x00000000, 0x00000000,
              GL_RGB, UNSUPPORTED, GL_UNSIGNED_SHORT }, 
        };

        bool found = false;

        for ( int i = 0; i < sizeof ( rgbFormats ) / sizeof ( RGBFormat ); i++ )
        {
            const RGBFormat& f = rgbFormats[ i ];
            if ( ddsd.ddpfPixelFormat.dwRGBBitCount     == f.bitCount &&
                 ddsd.ddpfPixelFormat.dwRBitMask        == f.rBitMask &&
                 ddsd.ddpfPixelFormat.dwGBitMask        == f.gBitMask &&
                 ddsd.ddpfPixelFormat.dwBBitMask        == f.bBitMask &&
                 ddsd.ddpfPixelFormat.dwRGBAlphaBitMask == f.aBitMask )
            {
                if ( f.internalFormat != UNSUPPORTED &&
                     f.pixelFormat    != UNSUPPORTED &&
                     f.dataType       != UNSUPPORTED )
                {
                    osg::notify(osg::INFO) << "ReadDDSFile info : format = " << f.name << std::endl;
                    internalFormat = f.internalFormat;
                    pixelFormat    = f.pixelFormat;
                    dataType       = f.dataType;
                    found = true;
                    break;
                }
                else
                {
                    osg::notify(osg::INFO) << "ReadDDSFile info : " << f.name
                                           << " format is not supported" << std::endl;
                    return NULL;                   
                }
            }            
        }

        if ( !found )
        {
            osg::notify(osg::WARN) << "ReadDDSFile warning: unhandled RGB pixel format in dds file, image not loaded" << std::endl;
            osg::notify(osg::INFO) << "ReadDDSFile info : ddsd.ddpfPixelFormat.dwRGBBitCount     = "
                                   << ddsd.ddpfPixelFormat.dwRGBBitCount << std::endl;
            osg::notify(osg::INFO) << "ReadDDSFile info : ddsd.ddpfPixelFormat.dwRBitMask        = 0x"
                                   << std::hex << std::setw(8) << std::setfill('0') 
                                   << ddsd.ddpfPixelFormat.dwRBitMask << std::endl;
            osg::notify(osg::INFO) << "ReadDDSFile info : ddsd.ddpfPixelFormat.dwGBitMask        = 0x"
                                   << std::hex << std::setw(8) << std::setfill('0') 
                                   << ddsd.ddpfPixelFormat.dwGBitMask << std::endl;
            osg::notify(osg::INFO) << "ReadDDSFile info : ddsd.ddpfPixelFormat.dwBBitMask        = 0x"
                                   << std::hex << std::setw(8) << std::setfill('0') 
                                   << ddsd.ddpfPixelFormat.dwBBitMask << std::endl;
            osg::notify(osg::INFO) << "ReadDDSFile info : ddsd.ddpfPixelFormat.dwRGBAlphaBitMask = 0x"
                                   << std::hex << std::setw(8) << std::setfill('0') 
                                   << ddsd.ddpfPixelFormat.dwRGBAlphaBitMask << std::dec << std::endl;
            return NULL;
        }
    }
    else if(ddsd.ddpfPixelFormat.dwFlags & DDPF_LUMINANCE)
    {
            internalFormat = usingAlpha ? GL_LUMINANCE_ALPHA : GL_LUMINANCE;
            pixelFormat    = usingAlpha ? GL_LUMINANCE_ALPHA : GL_LUMINANCE;
            if ( usingAlpha && ddsd.ddpfPixelFormat.dwLuminanceBitDepth == 8 )
            {
                osg::notify(osg::INFO) << "ReadDDSFile info : format = L4A4" << std::endl;
                pixelFormat = GL_LUMINANCE4_ALPHA4; // invalid enumerant?
            }
            else if ( usingAlpha && ddsd.ddpfPixelFormat.dwLuminanceBitDepth == 32 )
            {
                osg::notify(osg::INFO) << "ReadDDSFile info : format = L16A16" << std::endl;
                dataType = GL_UNSIGNED_SHORT;
            }
            else if ( !usingAlpha && ddsd.ddpfPixelFormat.dwLuminanceBitDepth == 16 )
            {
                osg::notify(osg::INFO) << "ReadDDSFile info : format = L16" << std::endl;
                dataType = GL_UNSIGNED_SHORT;
            }
            else if ( usingAlpha )
            {
                osg::notify(osg::INFO) << "ReadDDSFile info : format = L8A8" << std::endl;
            }
            else
            {
                osg::notify(osg::INFO) << "ReadDDSFile info : format = L8" << std::endl;
            }
//             else if ( ddsd.ddpfPixelFormat.dwLuminanceBitDepth == (usingAlpha ? 64 : 32) )
//             {
//                 dataType = GL_UNSIGNED_INT;
//             }
    }
    else if(ddsd.ddpfPixelFormat.dwFlags & DDPF_ALPHA)
    {
            osg::notify(osg::INFO) << "ReadDDSFile info : format = ALPHA" << std::endl;
            internalFormat = GL_ALPHA;
            pixelFormat    = GL_ALPHA;              
    }
    // Compressed formats
    else if(ddsd.ddpfPixelFormat.dwFlags & DDPF_FOURCC)
    {
        // TODO: Image::isImageTranslucent() doesn't work with S3TC compressed files
        switch(ddsd.ddpfPixelFormat.dwFourCC)
        {
        case FOURCC_DXT1:
            osg::notify(osg::INFO) << "ReadDDSFile info : format = DXT1" << std::endl;
            if (usingAlpha)
            {
                internalFormat = GL_COMPRESSED_RGBA_S3TC_DXT1_EXT;
                pixelFormat    = GL_COMPRESSED_RGBA_S3TC_DXT1_EXT;
            }
            else
            {
                internalFormat = GL_COMPRESSED_RGB_S3TC_DXT1_EXT;
                pixelFormat    = GL_COMPRESSED_RGB_S3TC_DXT1_EXT;
                checkIfUsingOneBitAlpha = true;
            }
            break;
        case FOURCC_DXT3:
            osg::notify(osg::INFO) << "ReadDDSFile info : format = DXT3" << std::endl;
            internalFormat = GL_COMPRESSED_RGBA_S3TC_DXT3_EXT;
            pixelFormat    = GL_COMPRESSED_RGBA_S3TC_DXT3_EXT;
            break;
        case FOURCC_DXT5:
            osg::notify(osg::INFO) << "ReadDDSFile info : format = DXT5" << std::endl;
            internalFormat = GL_COMPRESSED_RGBA_S3TC_DXT5_EXT;
            pixelFormat    = GL_COMPRESSED_RGBA_S3TC_DXT5_EXT;
            break;
        case 0x00000024: // A16B16G16R16
            osg::notify(osg::INFO) << "ReadDDSFile info : format = A16B16G16R16" << std::endl;
            internalFormat = GL_RGBA;
            pixelFormat    = GL_RGBA;
            dataType       = GL_UNSIGNED_SHORT;
            break;
        case 0x00000071: // A16B16G16R16F
            osg::notify(osg::INFO) << "ReadDDSFile info : format = A16B16G16R16F" << std::endl;
            internalFormat = GL_RGBA; // why no transparency?
            pixelFormat    = GL_RGBA;
            dataType       = GL_HALF_FLOAT_NV; 
            break;
        case 0x0000006E: // Q16W16V16U16
            osg::notify(osg::INFO) << "ReadDDSFile info : format = Q16W16V16U16" << std::endl;
            internalFormat = GL_RGBA;
            pixelFormat    = GL_RGBA;
            dataType       = GL_UNSIGNED_SHORT;
            break;
        case 0x00000070: // G16R16F
            osg::notify(osg::INFO) << "ReadDDSFile info : G16R16F format is not supported"
                                   << std::endl;
            return NULL;
//             internalFormat = GL_RGB;
//             pixelFormat    = must be GL_RED and GL_GREEN
//             dataType       = GL_HALF_FLOAT_NV;
            break;
        case 0x00000073: // G32R32F
            osg::notify(osg::INFO) << "ReadDDSFile info : G32R32F format is not supported"
                                   << std::endl;
            return NULL;
//             internalFormat = GL_RGB;
//             pixelFormat    = must be GL_RED and GL_GREEN
//             dataType       = GL_FLOAT;
            break;
        case 0x00000072: // R32F
            osg::notify(osg::INFO) << "ReadDDSFile info : format = R32F" << std::endl;
            internalFormat = GL_RGB;
            pixelFormat    = GL_RED;
            dataType       = GL_FLOAT;
            break;
        case 0x0000006F: // R16F
            osg::notify(osg::INFO) << "ReadDDSFile info : format = R16F" << std::endl;
            internalFormat = GL_RGB;
            pixelFormat    = GL_RED;
            dataType       = GL_HALF_FLOAT_NV;
            break;
        case 0x00000074: // A32B32G32R32F
            osg::notify(osg::INFO) << "ReadDDSFile info : format = A32B32G32R32F" << std::endl;
            internalFormat = GL_RGBA;
            pixelFormat    = GL_RGBA;
            dataType       = GL_FLOAT;
            break;
        case 0x00000075: // CxV8U8
            osg::notify(osg::INFO) << "ReadDDSFile info : CxV8U8 format is not supported" << std::endl;
            return NULL;

        case MAKEFOURCC( 'U', 'Y', 'V', 'Y' ): // not supported in OSG
        case MAKEFOURCC( 'U', 'Y', 'V', '2' ): // not supported in OSG
        case MAKEFOURCC( 'R', 'G', 'B', 'G' ): // R8G8_B8G8 -- what is it?
        case MAKEFOURCC( 'G', 'R', 'G', 'B' ): // G8R8_G8B8 -- what is it?
            //break;

        default:
            osg::notify(osg::WARN) << "ReadDDSFile warning: unhandled FOURCC pixel format ("
                                   << (char)((ddsd.ddpfPixelFormat.dwFourCC & 0x000000ff))
                                   << (char)((ddsd.ddpfPixelFormat.dwFourCC & 0x0000ff00) >> 8)
                                   << (char)((ddsd.ddpfPixelFormat.dwFourCC & 0x00ff0000) >> 16)
                                   << (char)((ddsd.ddpfPixelFormat.dwFourCC & 0xff000000) >> 24)
                                   << " = 0x" << std::hex << std::setw(8) << std::setfill('0')
                                   << ddsd.ddpfPixelFormat.dwFourCC << std::dec
                                   << ") in dds file, image not loaded." << std::endl;
            return NULL; 
        }
    }
    else 
    {
        osg::notify(osg::WARN) << "ReadDDSFile warning: unhandled pixel format (ddsd.ddpfPixelFormat.dwFlags"
                               << " = 0x" << std::hex << std::setw(8) << std::setfill('0')
                               << ddsd.ddpfPixelFormat.dwFlags << std::dec
                               << ") in dds file, image not loaded."<<std::endl;
        return NULL;
    }

    //###[afarre_051904]
    /*if (is3dImage)
        size = osg::Image::computeNumComponents(pixelFormat) * ddsd.dwWidth * ddsd.dwHeight * depth;


    //delayed allocation og image data after all checks
    unsigned char* imageData = new unsigned char [size];
    if(!imageData)
    {
        return NULL;
    }

    // Read image data
    _istream.read((char*)imageData, size);

    
    // NOTE: We need to set the image data before setting the mipmap data, this
    // is because the setImage method clears the _mipmapdata vector in osg::Image.
    // Set image data and properties.
    osgImage->setImage(s,t,r, internalFormat, pixelFormat, dataType, imageData, osg::Image::USE_NEW_DELETE);
    */

    // Now set mipmap data (offsets into image raw data)
    //###[afarre_051904]
    osg::Image::MipmapDataType mipmaps; 

    // Take care of mipmaps if any.
    if (ddsd.dwMipMapCount>1)
    {
        // Now set mipmap data (offsets into image raw data).
        //###[afarre_051904]osg::Image::MipmapDataType mipmaps;

        //This is to complete mipmap sequence until level Nx1

        //debugging messages        
        float power2_s = logf((float)s)/logf((float)2);
        float power2_t = logf((float)t)/logf((float)2);

        osg::notify(osg::INFO) << "ReadDDSFile info : ddsd.dwMipMapCount = "<<ddsd.dwMipMapCount<<std::endl;
        osg::notify(osg::INFO) << "ReadDDSFile info : s = "<<s<<std::endl;
        osg::notify(osg::INFO) << "ReadDDSFile info : t = "<<t<<std::endl;
        osg::notify(osg::INFO) << "ReadDDSFile info : power2_s="<<power2_s<<std::endl;
        osg::notify(osg::INFO) << "ReadDDSFile info : power2_t="<<power2_t<<std::endl;

        mipmaps.resize((unsigned int)osg::maximum(power2_s,power2_t),0);

        // Handle S3TC compressed mipmaps.
        if( (ddsd.ddpfPixelFormat.dwFlags & DDPF_FOURCC)
            &&
            (ddsd.ddpfPixelFormat.dwFourCC == FOURCC_DXT1 ||
             ddsd.ddpfPixelFormat.dwFourCC == FOURCC_DXT3 ||
             ddsd.ddpfPixelFormat.dwFourCC == FOURCC_DXT5))
        {
            int width = ddsd.dwWidth;
            int height = ddsd.dwHeight;
            int blockSize = (ddsd.ddpfPixelFormat.dwFourCC == FOURCC_DXT1) ? 8 : 16;
            int offset = 0;
            for (unsigned int k = 1; k < ddsd.dwMipMapCount && (width || height); ++k)
            {
                if (width == 0)
                    width = 1;
                if (height == 0)
                    height = 1;
                offset += (((width+3)/4) * ((height+3)/4) * blockSize);
                mipmaps[k-1] = offset;
                width >>= 1;
                height >>= 1;
            }
            //###[afarre_051904] osgImage->setMipmapData(mipmaps);
        }
        // Handle uncompressed mipmaps
        else
        {
            int offset = 0;
            int width = ddsd.dwWidth;
            int height = ddsd.dwHeight;
            for (unsigned int k = 1; k < ddsd.dwMipMapCount && (width || height); ++k)
            {
                if (width == 0)
                    width = 1;
                if (height == 0)
                    height = 1;
                offset += height *
                    osg::Image::computeRowWidthInBytes( width, pixelFormat, dataType, 1 );
                mipmaps[k-1] = offset;
                width >>= 1;
                height >>= 1;
            }
            //###[afarre_051904] osgImage->setMipmapData(mipmaps);
        }
    }

    osgImage->setImage(s,t,r, internalFormat, pixelFormat, dataType, 0, osg::Image::USE_NEW_DELETE);
    if (mipmaps.size()>0)  osgImage->setMipmapLevels(mipmaps);
    unsigned int size = osgImage->getTotalSizeInBytesIncludingMipmaps();

    osg::notify(osg::INFO) << "ReadDDSFile info : size = " << size << std::endl;
    
    if(size <= 0)
    {
        osg::notify(osg::WARN) << "ReadDDSFile warning: size <= 0" << std::endl;
        return NULL;
    }

    unsigned char* imageData = new unsigned char [size];
    if(!imageData)
    {
        osg::notify(osg::WARN) << "ReadDDSFile warning: imageData == NULL" << std::endl;
        return NULL;
    }

    // Read image data
    _istream.read((char*)imageData, size);

    // Check if alpha information embedded in the 8-byte encoding blocks
    if (checkIfUsingOneBitAlpha)
    {
        const DXT1TexelsBlock *texelsBlock = reinterpret_cast<const DXT1TexelsBlock*>(imageData);

        // Only do the check on the first mipmap level
        unsigned int numBlocks = mipmaps.size()>0 ? mipmaps[0] / 8 : size / 8;

        for (int i=numBlocks; i>0; --i, ++texelsBlock)
        {
            if (texelsBlock->color_0<=texelsBlock->color_1)
            {
                // Texture is using the 1-bit alpha encoding, so we need to update the assumed pixel format
                internalFormat = GL_COMPRESSED_RGBA_S3TC_DXT1_EXT;
                pixelFormat    = GL_COMPRESSED_RGBA_S3TC_DXT1_EXT;
                break;
            }
        }
    }

    osgImage->setImage(s,t,r, internalFormat, pixelFormat, dataType, imageData, osg::Image::USE_NEW_DELETE);
    if (mipmaps.size()>0)  osgImage->setMipmapLevels(mipmaps);
         
    // Return Image.
    return osgImage.release();
}


/*
osg::Image::MipmapDataType mipmaps;
osgImage->setMipmapData(mipmaps);
osgImage->setImage(s,t,r, internalFormat, pixelFormat, dataType, 0, osg::Image::USE_NEW_DELETE);
printf("INVENTO===> gtsibim:%d  grsib:%d   mi_size:%d   lPitch%d\n", 
    osgImage->getTotalSizeInBytesIncludingMipmaps(), 
    osgImage->getRowSizeInBytes(), size, ddsd.lPitch);
printf("CORRECTO**> gtsibim:%d  grsib:%d   mi_size:%d   lPitch%d\n", 
    osgImage->getTotalSizeInBytesIncludingMipmaps(), 
    osgImage->getRowSizeInBytes(), size, ddsd.lPitch);

 */






bool WriteDDSFile(const osg::Image *img, std::ostream& fout)
{

    // Initialize ddsd structure and its members 
    DDSURFACEDESC2 ddsd;
    DDPIXELFORMAT  ddpf;
    //DDCOLORKEY     ddckCKDestOverlay;
    //DDCOLORKEY     ddckCKDestBlt;
    //DDCOLORKEY     ddckCKSrcOverlay;
    //DDCOLORKEY     ddckCKSrcBlt;
    DDSCAPS2       ddsCaps;

    ddsd.dwSize = sizeof(ddsd);  
    ddpf.dwSize = sizeof(ddpf);

    // Default values and initialization of structures' flags
    unsigned int SD_flags = DDSD_CAPS | DDSD_HEIGHT | DDSD_WIDTH | DDSD_PIXELFORMAT;
    unsigned int CAPS_flags  = DDSCAPS_TEXTURE; 
    unsigned int PF_flags = 0;
    unsigned int CAPS2_flags = 0;

    // Get image properties
    unsigned int dataType       = img->getDataType();
    unsigned int pixelFormat    = img->getPixelFormat();
    //unsigned int internalFormat = img->getInternalTextureFormat();
    //unsigned int components     = osg::Image::computeNumComponents(pixelFormat);
    unsigned int pixelSize      = osg::Image::computePixelSizeInBits(pixelFormat, dataType);
    unsigned int imageSize      = img->getImageSizeInBytes();
    bool is3dImage = false;

    ddsd.dwWidth  = img->s();
    ddsd.dwHeight = img->t();
    int r = img->r();

    if(r > 1)  /* check for 3d image */
    {
        is3dImage = true;
        ddsd.dwDepth = r;
        SD_flags    |= DDSD_DEPTH;
        CAPS_flags  |= DDSCAPS_COMPLEX;
        CAPS2_flags |= DDSCAPS2_VOLUME;
    }

    // Determine format - set flags and ddsd, ddpf properties
    switch (pixelFormat)
    {
        //Uncompressed
    case GL_RGBA:
        {
            ddpf.dwRBitMask        = 0x000000ff;
            ddpf.dwGBitMask        = 0x0000ff00;
            ddpf.dwBBitMask        = 0x00ff0000;  
            ddpf.dwRGBAlphaBitMask = 0xff000000;
            PF_flags |= (DDPF_ALPHAPIXELS | DDPF_RGB);
            ddpf.dwRGBBitCount = pixelSize; 
            ddsd.lPitch = img->getRowSizeInBytes();
            SD_flags |= DDSD_PITCH;
        }
        break;
    case GL_BGRA:
        {
            ddpf.dwBBitMask        = 0x000000ff;
            ddpf.dwGBitMask        = 0x0000ff00;
            ddpf.dwRBitMask        = 0x00ff0000;  
            ddpf.dwRGBAlphaBitMask = 0xff000000;
            PF_flags |= (DDPF_ALPHAPIXELS | DDPF_RGB);
            ddpf.dwRGBBitCount = pixelSize; 
            ddsd.lPitch = img->getRowSizeInBytes();
            SD_flags |= DDSD_PITCH;
        }
        break;
    case GL_LUMINANCE_ALPHA:
        {
            ddpf.dwRBitMask         = 0x00ff0000;
            ddpf.dwRGBAlphaBitMask  = 0x000000ff;
            PF_flags |= (DDPF_ALPHAPIXELS | DDPF_LUMINANCE);  
            ddpf.dwRGBBitCount = pixelSize; 
            ddsd.lPitch = img->getRowSizeInBytes();
            SD_flags |= DDSD_PITCH;
        }
        break;
    case GL_RGB:
        {
            ddpf.dwRBitMask        = 0x000000ff;
            ddpf.dwGBitMask        = 0x0000ff00;
            ddpf.dwBBitMask        = 0x00ff0000;  
            PF_flags |= DDPF_RGB;
            ddpf.dwRGBBitCount = pixelSize;
            ddsd.lPitch = img->getRowSizeInBytes();
            SD_flags |= DDSD_PITCH;
        }
        break;
    case GL_LUMINANCE:
        {
            ddpf.dwRBitMask         = 0x00ff0000;
            PF_flags |= DDPF_LUMINANCE;
            ddpf.dwRGBBitCount = pixelSize;
            ddsd.lPitch = img->getRowSizeInBytes();
            SD_flags |= DDSD_PITCH;
        }
        break;
    case GL_ALPHA:
        {
            ddpf.dwRGBAlphaBitMask  = 0x000000ff;
            PF_flags |= DDPF_ALPHA;
            ddpf.dwRGBBitCount = pixelSize;
            ddsd.lPitch = img->getRowSizeInBytes();
            SD_flags |= DDSD_PITCH;
        }
        break;

        //Compressed
    case GL_COMPRESSED_RGBA_S3TC_DXT1_EXT:
        {
            ddpf.dwFourCC = FOURCC_DXT1;
            PF_flags |= (DDPF_ALPHAPIXELS | DDPF_FOURCC);
            ddsd.dwLinearSize = imageSize;
            SD_flags |= DDSD_LINEARSIZE;
        }
        break;
    case GL_COMPRESSED_RGBA_S3TC_DXT3_EXT:
        {
            ddpf.dwFourCC = FOURCC_DXT3;
            PF_flags |= (DDPF_ALPHAPIXELS | DDPF_FOURCC);
            ddsd.dwLinearSize = imageSize;
            SD_flags |= DDSD_LINEARSIZE;
        }
        break;
    case GL_COMPRESSED_RGBA_S3TC_DXT5_EXT:
        {
            ddpf.dwFourCC = FOURCC_DXT5;
            PF_flags |= (DDPF_ALPHAPIXELS | DDPF_FOURCC);
            ddsd.dwLinearSize = imageSize;
            SD_flags |= DDSD_LINEARSIZE;
        }
        break;
    case GL_COMPRESSED_RGB_S3TC_DXT1_EXT:
        {
            ddpf.dwFourCC = FOURCC_DXT1;
            PF_flags |= DDPF_FOURCC;  /* No alpha here */
            ddsd.dwLinearSize = imageSize;
            SD_flags |= DDSD_LINEARSIZE;
        }
        break;
    default:
        osg::notify(osg::WARN)<<"Warning:: unhandled pixel format in image, file cannot be written."<<std::endl;
        return false;
    }

   
    // set even more flags
    if(img->isMipmap() && !is3dImage)
    {
        SD_flags   |= DDSD_MIPMAPCOUNT;
        CAPS_flags |= DDSCAPS_COMPLEX | DDSCAPS_MIPMAP;
        ddsd.dwMipMapCount = img->getNumMipmapLevels();
    }


    // Assign flags and structure members of ddsd
    ddsd.dwFlags    = SD_flags;
    ddpf.dwFlags    = PF_flags;
    ddsCaps.dwCaps  = CAPS_flags;
    ddsCaps.dwCaps2 = CAPS2_flags;

    ddsd.ddpfPixelFormat = ddpf;
    ddsd.ddsCaps = ddsCaps;


    // Write DDS file
    fout.write("DDS ", 4); /* write FOURCC */
    fout.write(reinterpret_cast<char*>(&ddsd), sizeof(ddsd)); /* write file header */

    //    int isize = img->getTotalSizeInBytesIncludingMipmaps();
    if(!is3dImage)
    {
        fout.write(reinterpret_cast<const char*>(img->data()), img->getTotalSizeInBytesIncludingMipmaps());
    }
    else  /* 3d image */
    {
        for(int i = 0; i < r; ++i)
        {
            fout.write(reinterpret_cast<const char*>(img->data(0, 0, i)), imageSize);
        }
    }

    // Check for correct saving
    if (fout.fail())
    {
        return false;
    }

    // If we get that far the file was saved properly //
    return true; 
}


class ReaderWriterDDS : public osgDB::ReaderWriter
{
public:
    virtual const char* className() const
    { 
        return "DDS Image Reader/Writer"; 
    }

    virtual bool acceptsExtension(const std::string& extension) const
    { 
        return osgDB::equalCaseInsensitive(extension,"dds"); 
    }

    virtual ReadResult readObject(const std::string& file, const osgDB::ReaderWriter::Options* options) const
    {
        return readImage(file,options);
    }

    virtual ReadResult readObject(std::istream& fin, const Options* options) const
    {
        return readImage(fin,options);
    }

    virtual ReadResult readImage(const std::string& file, const osgDB::ReaderWriter::Options* options) const
    {
        std::string ext = osgDB::getLowerCaseFileExtension(file);
        if (!acceptsExtension(ext)) return ReadResult::FILE_NOT_HANDLED;

        std::string fileName = osgDB::findDataFile( file, options );
    
        if (fileName.empty()) return ReadResult::FILE_NOT_FOUND;
        
        std::ifstream stream(fileName.c_str(), std::ios::in | std::ios::binary);
        if(!stream) return ReadResult::FILE_NOT_HANDLED;
        ReadResult rr = readImage(stream, options);
        if(rr.validImage()) rr.getImage()->setFileName(file);
        return rr;
    }

    virtual ReadResult readImage(std::istream& fin, const Options* options) const
    {
        osg::Image* osgImage = ReadDDSFile(fin);
        if (osgImage==NULL) return ReadResult::FILE_NOT_HANDLED;
        
        if (options && options->getOptionString().find("dds_flip")!=std::string::npos)
        {
            osgImage->flipVertical();
        }
        
        return osgImage;
    }

    virtual WriteResult writeObject(const osg::Object& object,const std::string& file, const osgDB::ReaderWriter::Options* options) const
    {
        const osg::Image* image = dynamic_cast<const osg::Image*>(&object);
        if (!image) return WriteResult::FILE_NOT_HANDLED;

        return writeImage(*image,file,options);
    }

    virtual WriteResult writeObject(const osg::Object& object,std::ostream& fout,const Options* options) const
    {
        const osg::Image* image = dynamic_cast<const osg::Image*>(&object);
        if (!image) return WriteResult::FILE_NOT_HANDLED;

        return writeImage(*image,fout,options);
    }


    virtual WriteResult writeImage(const osg::Image &image,const std::string& file, const osgDB::ReaderWriter::Options* options) const
    {
        std::string ext = osgDB::getFileExtension(file);
        if (!acceptsExtension(ext)) return WriteResult::FILE_NOT_HANDLED;

        std::ofstream fout(file.c_str(), std::ios::out | std::ios::binary);
        if(!fout) return WriteResult::ERROR_IN_WRITING_FILE;

        return writeImage(image,fout,options);
    }

    virtual WriteResult writeImage(const osg::Image& image,std::ostream& fout,const Options*) const
    {
        bool success = WriteDDSFile(&image, fout);

        if(success)
            return WriteResult::FILE_SAVED;
        else
            return WriteResult::ERROR_IN_WRITING_FILE;
    }
};

// now register with Registry to instantiate the above
// reader/writer.
REGISTER_OSGPLUGIN(dds, ReaderWriterDDS)
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