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KImgIO

dds.cpp

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/* This file is part of the KDE project
   Copyright (C) 2003 Ignacio Castaño <castano@ludicon.com>

   This program is free software; you can redistribute it and/or
   modify it under the terms of the Lesser GNU General Public
   License as published by the Free Software Foundation; either
   version 2 of the License, or (at your option) any later version.

   Almost all this code is based on nVidia's DDS-loading example
   and the DevIl's source code by Denton Woods.
*/

/* this code supports:
 * reading:
 *     rgb and dxt dds files
 *     cubemap dds files
 *     volume dds files -- TODO
 * writing:
 *     rgb dds files only -- TODO
 */

#include "dds.h"

#include <qimage.h>
#include <qdatastream.h>

#include <kglobal.h>
#include <kdebug.h>

#include <math.h> // sqrtf

#ifndef __USE_ISOC99
#define sqrtf(x) ((float)sqrt(x))
#endif

typedef Q_UINT32 uint;
typedef Q_UINT16 ushort;
typedef Q_UINT8 uchar;

namespace { // Private.

#if !defined(MAKEFOURCC)
#   define MAKEFOURCC(ch0, ch1, ch2, ch3) \
        (uint(uchar(ch0)) | (uint(uchar(ch1)) << 8) | \
        (uint(uchar(ch2)) << 16) | (uint(uchar(ch3)) << 24 ))
#endif

#define HORIZONTAL 1
#define VERTICAL 2
#define CUBE_LAYOUT HORIZONTAL

    struct Color8888
    {
        uchar r, g, b, a;
    };

    union Color565
    {
        struct {
            ushort b : 5;
            ushort g : 6;
            ushort r : 5;
        } c;
        ushort u;
    };

    union Color1555 {
        struct {
            ushort b : 5;
            ushort g : 5;
            ushort r : 5;
            ushort a : 1;
        } c;
        ushort u;
    };

    union Color4444 {
        struct {
            ushort b : 4;
            ushort g : 4;
            ushort r : 4;
            ushort a : 4;
        } c;
        ushort u;
    };


    static const uint FOURCC_DDS = MAKEFOURCC('D', 'D', 'S', ' ');
    static const uint FOURCC_DXT1 = MAKEFOURCC('D', 'X', 'T', '1');
    static const uint FOURCC_DXT2 = MAKEFOURCC('D', 'X', 'T', '2');
    static const uint FOURCC_DXT3 = MAKEFOURCC('D', 'X', 'T', '3');
    static const uint FOURCC_DXT4 = MAKEFOURCC('D', 'X', 'T', '4');
    static const uint FOURCC_DXT5 = MAKEFOURCC('D', 'X', 'T', '5');
    static const uint FOURCC_RXGB = MAKEFOURCC('R', 'X', 'G', 'B');
    static const uint FOURCC_ATI2 = MAKEFOURCC('A', 'T', 'I', '2');

    static const uint DDSD_CAPS = 0x00000001l;
    static const uint DDSD_PIXELFORMAT = 0x00001000l;
    static const uint DDSD_WIDTH = 0x00000004l;
    static const uint DDSD_HEIGHT = 0x00000002l;
    static const uint DDSD_PITCH = 0x00000008l;

    static const uint DDSCAPS_TEXTURE = 0x00001000l;
    static const uint DDSCAPS2_VOLUME = 0x00200000l;
    static const uint DDSCAPS2_CUBEMAP = 0x00000200l;

    static const uint DDSCAPS2_CUBEMAP_POSITIVEX = 0x00000400l;
    static const uint DDSCAPS2_CUBEMAP_NEGATIVEX = 0x00000800l;
    static const uint DDSCAPS2_CUBEMAP_POSITIVEY = 0x00001000l;
    static const uint DDSCAPS2_CUBEMAP_NEGATIVEY = 0x00002000l;
    static const uint DDSCAPS2_CUBEMAP_POSITIVEZ = 0x00004000l;
    static const uint DDSCAPS2_CUBEMAP_NEGATIVEZ = 0x00008000l;

    static const uint DDPF_RGB = 0x00000040l;
    static const uint DDPF_FOURCC = 0x00000004l;
    static const uint DDPF_ALPHAPIXELS = 0x00000001l;

    enum DDSType {
        DDS_A8R8G8B8 = 0,
        DDS_A1R5G5B5 = 1,
        DDS_A4R4G4B4 = 2,
        DDS_R8G8B8 = 3,
        DDS_R5G6B5 = 4,
        DDS_DXT1 = 5,
        DDS_DXT2 = 6,
        DDS_DXT3 = 7,
        DDS_DXT4 = 8,
        DDS_DXT5 = 9,
        DDS_RXGB = 10,
        DDS_ATI2 = 11,
        DDS_UNKNOWN
    };


    struct DDSPixelFormat {
        uint size;
        uint flags;
        uint fourcc;
        uint bitcount;
        uint rmask;
        uint gmask;
        uint bmask;
        uint amask;
    };

    static QDataStream & operator>> ( QDataStream & s, DDSPixelFormat & pf )
    {
        s >> pf.size;
        s >> pf.flags;
        s >> pf.fourcc;
        s >> pf.bitcount;
        s >> pf.rmask;
        s >> pf.gmask;
        s >> pf.bmask;
        s >> pf.amask;
        return s;
    }

    struct DDSCaps {
        uint caps1;
        uint caps2;
        uint caps3;
        uint caps4;
    };

    static QDataStream & operator>> ( QDataStream & s, DDSCaps & caps )
    {
        s >> caps.caps1;
        s >> caps.caps2;
        s >> caps.caps3;
        s >> caps.caps4;
        return s;
    }

    struct DDSHeader {
        uint size;
        uint flags;
        uint height;
        uint width;
        uint pitch;
        uint depth;
        uint mipmapcount;
        uint reserved[11];
        DDSPixelFormat pf;
        DDSCaps caps;
        uint notused;
    };

    static QDataStream & operator>> ( QDataStream & s, DDSHeader & header )
    {
        s >> header.size;
        s >> header.flags;
        s >> header.height;
        s >> header.width;
        s >> header.pitch;
        s >> header.depth;
        s >> header.mipmapcount;
        for( int i = 0; i < 11; i++ ) {
            s >> header.reserved[i];
        }
        s >> header.pf;
        s >> header.caps;
        s >> header.notused;
        return s;
    }

    static bool IsValid( const DDSHeader & header )
    {
        if( header.size != 124 ) {
            return false;
        }
        const uint required = (DDSD_WIDTH|DDSD_HEIGHT|DDSD_CAPS|DDSD_PIXELFORMAT);
        if( (header.flags & required) != required ) {
            return false;
        }
        if( header.pf.size != 32 ) {
            return false;
        }
        if( !(header.caps.caps1 & DDSCAPS_TEXTURE) ) {
            return false;
        }
        return true;
    }


    // Get supported type. We currently support 10 different types.
    static DDSType GetType( const DDSHeader & header )
    {
        if( header.pf.flags & DDPF_RGB ) {
            if( header.pf.flags & DDPF_ALPHAPIXELS ) {
                switch( header.pf.bitcount ) {
                    case 16:
                        return (header.pf.amask == 0x8000) ? DDS_A1R5G5B5 : DDS_A4R4G4B4;
                    case 32:
                        return DDS_A8R8G8B8;
                }
            }
            else {
                switch( header.pf.bitcount ) {
                    case 16:
                        return DDS_R5G6B5;
                    case 24:
                        return DDS_R8G8B8;
                }
            }
        }
        else if( header.pf.flags & DDPF_FOURCC ) {
            switch( header.pf.fourcc ) {
                case FOURCC_DXT1:
                    return DDS_DXT1;
                case FOURCC_DXT2:
                    return DDS_DXT2;
                case FOURCC_DXT3:
                    return DDS_DXT3;
                case FOURCC_DXT4:
                    return DDS_DXT4;
                case FOURCC_DXT5:
                    return DDS_DXT5;
                case FOURCC_RXGB:
                    return DDS_RXGB;
                case FOURCC_ATI2:
                    return DDS_ATI2;
            }
        }
        return DDS_UNKNOWN;
    }


    static bool HasAlpha( const DDSHeader & header )
    {
        return header.pf.flags & DDPF_ALPHAPIXELS;
    }

    static bool IsCubeMap( const DDSHeader & header )
    {
        return header.caps.caps2 & DDSCAPS2_CUBEMAP;
    }

    static bool IsSupported( const DDSHeader & header )
    {
        if( header.caps.caps2 & DDSCAPS2_VOLUME ) {
            return false;
        }
        if( GetType(header) == DDS_UNKNOWN ) {
            return false;
        }
        return true;
    }


    static bool LoadA8R8G8B8( QDataStream & s, const DDSHeader & header, QImage & img  )
    {
        const uint w = header.width;
        const uint h = header.height;

        for( uint y = 0; y < h; y++ ) {
            QRgb * scanline = (QRgb *) img.scanLine( y );
            for( uint x = 0; x < w; x++ ) {
                uchar r, g, b, a;
                s >> b >> g >> r >> a;
                scanline[x] = qRgba(r, g, b, a);
            }
        }

        return true;
    }

    static bool LoadR8G8B8( QDataStream & s, const DDSHeader & header, QImage & img )
    {
        const uint w = header.width;
        const uint h = header.height;

        for( uint y = 0; y < h; y++ ) {
            QRgb * scanline = (QRgb *) img.scanLine( y );
            for( uint x = 0; x < w; x++ ) {
                uchar r, g, b;
                s >> b >> g >> r;
                scanline[x] = qRgb(r, g, b);
            }
        }

        return true;
    }

    static bool LoadA1R5G5B5( QDataStream & s, const DDSHeader & header, QImage & img )
    {
        const uint w = header.width;
        const uint h = header.height;

        for( uint y = 0; y < h; y++ ) {
            QRgb * scanline = (QRgb *) img.scanLine( y );
            for( uint x = 0; x < w; x++ ) {
                Color1555 color;
                s >> color.u;
                uchar a = (color.c.a != 0) ? 0xFF : 0;
                uchar r = (color.c.r << 3) | (color.c.r >> 2);
                uchar g = (color.c.g << 3) | (color.c.g >> 2);
                uchar b = (color.c.b << 3) | (color.c.b >> 2);
                scanline[x] = qRgba(r, g, b, a);
            }
        }

        return true;
    }

    static bool LoadA4R4G4B4( QDataStream & s, const DDSHeader & header, QImage & img )
    {
        const uint w = header.width;
        const uint h = header.height;

        for( uint y = 0; y < h; y++ ) {
            QRgb * scanline = (QRgb *) img.scanLine( y );
            for( uint x = 0; x < w; x++ ) {
                Color4444 color;
                s >> color.u;
                uchar a = (color.c.a << 4) | color.c.a;
                uchar r = (color.c.r << 4) | color.c.r;
                uchar g = (color.c.g << 4) | color.c.g;
                uchar b = (color.c.b << 4) | color.c.b;
                scanline[x] = qRgba(r, g, b, a);
            }
        }

        return true;
    }

    static bool LoadR5G6B5( QDataStream & s, const DDSHeader & header, QImage & img )
    {
        const uint w = header.width;
        const uint h = header.height;

        for( uint y = 0; y < h; y++ ) {
            QRgb * scanline = (QRgb *) img.scanLine( y );
            for( uint x = 0; x < w; x++ ) {
                Color565 color;
                s >> color.u;
                uchar r = (color.c.r << 3) | (color.c.r >> 2);
                uchar g = (color.c.g << 2) | (color.c.g >> 4);
                uchar b = (color.c.b << 3) | (color.c.b >> 2);
                scanline[x] = qRgb(r, g, b);
            }
        }

        return true;
    }

    static QDataStream & operator>> ( QDataStream & s, Color565 & c )
    {
        return s >> c.u;
    }


    struct BlockDXT
    {
        Color565 col0;
        Color565 col1;
        uchar row[4];

        void GetColors( Color8888 color_array[4] )
        {
            color_array[0].r = (col0.c.r << 3) | (col0.c.r >> 2);
            color_array[0].g = (col0.c.g << 2) | (col0.c.g >> 4);
            color_array[0].b = (col0.c.b << 3) | (col0.c.b >> 2);
            color_array[0].a = 0xFF;

            color_array[1].r = (col1.c.r << 3) | (col1.c.r >> 2);
            color_array[1].g = (col1.c.g << 2) | (col1.c.g >> 4);
            color_array[1].b = (col1.c.b << 3) | (col1.c.b >> 2);
            color_array[1].a = 0xFF;

            if( col0.u > col1.u ) {
                // Four-color block: derive the other two colors.
                color_array[2].r = (2 * color_array[0].r + color_array[1].r) / 3;
                color_array[2].g = (2 * color_array[0].g + color_array[1].g) / 3;
                color_array[2].b = (2 * color_array[0].b + color_array[1].b) / 3;
                color_array[2].a = 0xFF;

                color_array[3].r = (2 * color_array[1].r + color_array[0].r) / 3;
                color_array[3].g = (2 * color_array[1].g + color_array[0].g) / 3;
                color_array[3].b = (2 * color_array[1].b + color_array[0].b) / 3;
                color_array[3].a = 0xFF;
            }
            else {
                // Three-color block: derive the other color.
                color_array[2].r = (color_array[0].r + color_array[1].r) / 2;
                color_array[2].g = (color_array[0].g + color_array[1].g) / 2;
                color_array[2].b = (color_array[0].b + color_array[1].b) / 2;
                color_array[2].a = 0xFF;

                // Set all components to 0 to match DXT specs.
                color_array[3].r = 0x00; // color_array[2].r;
                color_array[3].g = 0x00; // color_array[2].g;
                color_array[3].b = 0x00; // color_array[2].b;
                color_array[3].a = 0x00;
            }
        }
    };


    static QDataStream & operator>> ( QDataStream & s, BlockDXT & c )
    {
        return s >> c.col0 >> c.col1 >> c.row[0] >> c.row[1] >> c.row[2] >> c.row[3];
    }

    struct BlockDXTAlphaExplicit {
        ushort row[4];
    };

    static QDataStream & operator>> ( QDataStream & s, BlockDXTAlphaExplicit & c )
    {
        return s >> c.row[0] >> c.row[1] >> c.row[2] >> c.row[3];
    }

    struct BlockDXTAlphaLinear {
        uchar alpha0;
        uchar alpha1;
        uchar bits[6];

        void GetAlphas( uchar alpha_array[8] )
        {
            alpha_array[0] = alpha0;
            alpha_array[1] = alpha1;

            // 8-alpha or 6-alpha block?
            if( alpha_array[0] > alpha_array[1] )
            {
                // 8-alpha block:  derive the other 6 alphas.
                // 000 = alpha_0, 001 = alpha_1, others are interpolated

                alpha_array[2] = ( 6 * alpha0 +     alpha1) / 7;    // bit code 010
                alpha_array[3] = ( 5 * alpha0 + 2 * alpha1) / 7;    // Bit code 011
                alpha_array[4] = ( 4 * alpha0 + 3 * alpha1) / 7;    // Bit code 100
                alpha_array[5] = ( 3 * alpha0 + 4 * alpha1) / 7;    // Bit code 101
                alpha_array[6] = ( 2 * alpha0 + 5 * alpha1) / 7;    // Bit code 110
                alpha_array[7] = (     alpha0 + 6 * alpha1) / 7;    // Bit code 111
            }
            else
            {
                // 6-alpha block:  derive the other alphas.
                // 000 = alpha_0, 001 = alpha_1, others are interpolated

                alpha_array[2] = (4 * alpha0 +     alpha1) / 5;     // Bit code 010
                alpha_array[3] = (3 * alpha0 + 2 * alpha1) / 5;     // Bit code 011
                alpha_array[4] = (2 * alpha0 + 3 * alpha1) / 5;     // Bit code 100
                alpha_array[5] = (    alpha0 + 4 * alpha1) / 5;     // Bit code 101
                alpha_array[6] = 0x00;                              // Bit code 110
                alpha_array[7] = 0xFF;                              // Bit code 111
            }
        }

        void GetBits( uchar bit_array[16] )
        {
            uint b = (uint &) bits[0];
            bit_array[0] = uchar(b & 0x07); b >>= 3;
            bit_array[1] = uchar(b & 0x07); b >>= 3;
            bit_array[2] = uchar(b & 0x07); b >>= 3;
            bit_array[3] = uchar(b & 0x07); b >>= 3;
            bit_array[4] = uchar(b & 0x07); b >>= 3;
            bit_array[5] = uchar(b & 0x07); b >>= 3;
            bit_array[6] = uchar(b & 0x07); b >>= 3;
            bit_array[7] = uchar(b & 0x07); b >>= 3;

            b = (uint &) bits[3];
            bit_array[8] = uchar(b & 0x07); b >>= 3;
            bit_array[9] = uchar(b & 0x07); b >>= 3;
            bit_array[10] = uchar(b & 0x07); b >>= 3;
            bit_array[11] = uchar(b & 0x07); b >>= 3;
            bit_array[12] = uchar(b & 0x07); b >>= 3;
            bit_array[13] = uchar(b & 0x07); b >>= 3;
            bit_array[14] = uchar(b & 0x07); b >>= 3;
            bit_array[15] = uchar(b & 0x07); b >>= 3;
        }
    };

    static QDataStream & operator>> ( QDataStream & s, BlockDXTAlphaLinear & c )
    {
        s >> c.alpha0 >> c.alpha1;
        return s >> c.bits[0] >> c.bits[1] >> c.bits[2] >> c.bits[3] >> c.bits[4] >> c.bits[5];
    }

    static bool LoadDXT1( QDataStream & s, const DDSHeader & header, QImage & img )
    {
        const uint w = header.width;
        const uint h = header.height;

        BlockDXT block;
        QRgb * scanline[4];

        for( uint y = 0; y < h; y += 4 ) {
            for( uint j = 0; j < 4; j++ ) {
                scanline[j] = (QRgb *) img.scanLine( y + j );
            }
            for( uint x = 0; x < w; x += 4 ) {

                // Read 64bit color block.
                s >> block;

                // Decode color block.
                Color8888 color_array[4];
                block.GetColors(color_array);

                // bit masks = 00000011, 00001100, 00110000, 11000000
                const uint masks[4] = { 3, 3<<2, 3<<4, 3<<6 };
                const int shift[4] = { 0, 2, 4, 6 };

                // Write color block.
                for( uint j = 0; j < 4; j++ ) {
                    for( uint i = 0; i < 4; i++ ) {
                        if( img.valid( x+i, y+j ) ) {
                            uint idx = (block.row[j] & masks[i]) >> shift[i];
                            scanline[j][x+i] = qRgba(color_array[idx].r, color_array[idx].g, color_array[idx].b, color_array[idx].a);
                        }
                    }
                }
            }
        }
        return true;
    }

    static bool LoadDXT3( QDataStream & s, const DDSHeader & header, QImage & img )
    {
        const uint w = header.width;
        const uint h = header.height;

        BlockDXT block;
        BlockDXTAlphaExplicit alpha;
        QRgb * scanline[4];

        for( uint y = 0; y < h; y += 4 ) {
            for( uint j = 0; j < 4; j++ ) {
                scanline[j] = (QRgb *) img.scanLine( y + j );
            }
            for( uint x = 0; x < w; x += 4 ) {

                // Read 128bit color block.
                s >> alpha;
                s >> block;

                // Decode color block.
                Color8888 color_array[4];
                block.GetColors(color_array);

                // bit masks = 00000011, 00001100, 00110000, 11000000
                const uint masks[4] = { 3, 3<<2, 3<<4, 3<<6 };
                const int shift[4] = { 0, 2, 4, 6 };

                // Write color block.
                for( uint j = 0; j < 4; j++ ) {
                    ushort a = alpha.row[j];
                    for( uint i = 0; i < 4; i++ ) {
                        if( img.valid( x+i, y+j ) ) {
                            uint idx = (block.row[j] & masks[i]) >> shift[i];
                            color_array[idx].a = a & 0x0f;
                            color_array[idx].a = color_array[idx].a | (color_array[idx].a << 4);
                            scanline[j][x+i] = qRgba(color_array[idx].r, color_array[idx].g, color_array[idx].b, color_array[idx].a);
                        }
                        a >>= 4;
                    }
                }
            }
        }
        return true;
    }

    static bool LoadDXT2( QDataStream & s, const DDSHeader & header, QImage & img )
    {
        if( !LoadDXT3(s, header, img) ) return false;
        //UndoPremultiplyAlpha(img);
        return true;
    }

    static bool LoadDXT5( QDataStream & s, const DDSHeader & header, QImage & img )
    {
        const uint w = header.width;
        const uint h = header.height;

        BlockDXT block;
        BlockDXTAlphaLinear alpha;
        QRgb * scanline[4];

        for( uint y = 0; y < h; y += 4 ) {
            for( uint j = 0; j < 4; j++ ) {
                scanline[j] = (QRgb *) img.scanLine( y + j );
            }
            for( uint x = 0; x < w; x += 4 ) {

                // Read 128bit color block.
                s >> alpha;
                s >> block;

                // Decode color block.
                Color8888 color_array[4];
                block.GetColors(color_array);

                uchar alpha_array[8];
                alpha.GetAlphas(alpha_array);

                uchar bit_array[16];
                alpha.GetBits(bit_array);

                // bit masks = 00000011, 00001100, 00110000, 11000000
                const uint masks[4] = { 3, 3<<2, 3<<4, 3<<6 };
                const int shift[4] = { 0, 2, 4, 6 };

                // Write color block.
                for( uint j = 0; j < 4; j++ ) {
                    for( uint i = 0; i < 4; i++ ) {
                        if( img.valid( x+i, y+j ) ) {
                            uint idx = (block.row[j] & masks[i]) >> shift[i];
                            color_array[idx].a = alpha_array[bit_array[j*4+i]];
                            scanline[j][x+i] = qRgba(color_array[idx].r, color_array[idx].g, color_array[idx].b, color_array[idx].a);
                        }
                    }
                }
            }
        }

        return true;
    }
    static bool LoadDXT4( QDataStream & s, const DDSHeader & header, QImage & img )
    {
        if( !LoadDXT5(s, header, img) ) return false;
        //UndoPremultiplyAlpha(img);
        return true;
    }

    static bool LoadRXGB( QDataStream & s, const DDSHeader & header, QImage & img )
    {
        const uint w = header.width;
        const uint h = header.height;

        BlockDXT block;
        BlockDXTAlphaLinear alpha;
        QRgb * scanline[4];

        for( uint y = 0; y < h; y += 4 ) {
            for( uint j = 0; j < 4; j++ ) {
                scanline[j] = (QRgb *) img.scanLine( y + j );
            }
            for( uint x = 0; x < w; x += 4 ) {

                // Read 128bit color block.
                s >> alpha;
                s >> block;

                // Decode color block.
                Color8888 color_array[4];
                block.GetColors(color_array);

                uchar alpha_array[8];
                alpha.GetAlphas(alpha_array);

                uchar bit_array[16];
                alpha.GetBits(bit_array);

                // bit masks = 00000011, 00001100, 00110000, 11000000
                const uint masks[4] = { 3, 3<<2, 3<<4, 3<<6 };
                const int shift[4] = { 0, 2, 4, 6 };

                // Write color block.
                for( uint j = 0; j < 4; j++ ) {
                    for( uint i = 0; i < 4; i++ ) {
                        if( img.valid( x+i, y+j ) ) {
                            uint idx = (block.row[j] & masks[i]) >> shift[i];
                            color_array[idx].a = alpha_array[bit_array[j*4+i]];
                            scanline[j][x+i] = qRgb(color_array[idx].a, color_array[idx].g, color_array[idx].b);
                        }
                    }
                }
            }
        }

        return true;
    }

    static bool LoadATI2( QDataStream & s, const DDSHeader & header, QImage & img )
    {
        const uint w = header.width;
        const uint h = header.height;

        BlockDXTAlphaLinear xblock;
        BlockDXTAlphaLinear yblock;
        QRgb * scanline[4];

        for( uint y = 0; y < h; y += 4 ) {
            for( uint j = 0; j < 4; j++ ) {
                scanline[j] = (QRgb *) img.scanLine( y + j );
            }
            for( uint x = 0; x < w; x += 4 ) {

                // Read 128bit color block.
                s >> xblock;
                s >> yblock;

                // Decode color block.
                uchar xblock_array[8];
                xblock.GetAlphas(xblock_array);

                uchar xbit_array[16];
                xblock.GetBits(xbit_array);

                uchar yblock_array[8];
                yblock.GetAlphas(yblock_array);

                uchar ybit_array[16];
                yblock.GetBits(ybit_array);

                // Write color block.
                for( uint j = 0; j < 4; j++ ) {
                    for( uint i = 0; i < 4; i++ ) {
                        if( img.valid( x+i, y+j ) ) {
                            const uchar nx = xblock_array[xbit_array[j*4+i]];
                            const uchar ny = yblock_array[ybit_array[j*4+i]];
                            
                            const float fx = float(nx) / 127.5f - 1.0f;
                            const float fy = float(ny) / 127.5f - 1.0f;
                            const float fz = sqrtf(1.0f - fx*fx - fy*fy);
                            const uchar nz = uchar((fz + 1.0f) * 127.5f);
                            
                            scanline[j][x+i] = qRgb(nx, ny, nz);
                        }
                    }
                }
            }
        }

        return true;
    }



    typedef bool (* TextureLoader)( QDataStream & s, const DDSHeader & header, QImage & img );

    // Get an appropiate texture loader for the given type.
    static TextureLoader GetTextureLoader( DDSType type ) {
        switch( type ) {
            case DDS_A8R8G8B8:
                return LoadA8R8G8B8;
            case DDS_A1R5G5B5:
                return LoadA1R5G5B5;
            case DDS_A4R4G4B4:
                return LoadA4R4G4B4;
            case DDS_R8G8B8:
                return LoadR8G8B8;
            case DDS_R5G6B5:
                return LoadR5G6B5;
            case DDS_DXT1:
                return LoadDXT1;
            case DDS_DXT2:
                return LoadDXT2;
            case DDS_DXT3:
                return LoadDXT3;
            case DDS_DXT4:
                return LoadDXT4;
            case DDS_DXT5:
                return LoadDXT5;
            case DDS_RXGB:
                return LoadRXGB;
            case DDS_ATI2:
                return LoadATI2;
            default:
                return NULL;
        };
    }


    // Load a 2d texture.
    static bool LoadTexture( QDataStream & s, const DDSHeader & header, QImage & img )
    {
        // Create dst image.
        if( !img.create( header.width, header.height, 32 )) {
            return false;
        }

        // Read image.
        DDSType type = GetType( header );

        // Enable alpha buffer for transparent or DDS images.
        if( HasAlpha( header ) || type >= DDS_DXT1 ) {
            img.setAlphaBuffer( true );
        }

        TextureLoader loader = GetTextureLoader( type );
        if( loader == NULL ) {
            return false;
        }

        return loader( s, header, img );
    }


    static int FaceOffset( const DDSHeader & header ) {

        DDSType type = GetType( header );

        int mipmap = kMax(int(header.mipmapcount), 1);
        int size = 0;
        int w = header.width;
        int h = header.height;
        
        if( type >= DDS_DXT1 ) {
            int multiplier = (type == DDS_DXT1) ? 8 : 16;
            do {
                int face_size = kMax(w/4,1) * kMax(h/4,1) * multiplier;
                size += face_size;
                w >>= 1;
                h >>= 1;
            } while( --mipmap );
        }
        else {
            int multiplier = header.pf.bitcount / 8;
            do {
                int face_size = w * h * multiplier;
                size += face_size;
                w = kMax( w>>1, 1 );
                h = kMax( h>>1, 1 );
            } while( --mipmap );
        }

        return size;
    }

#if CUBE_LAYOUT == HORIZONTAL
    static int face_offset[6][2] = { {2, 1}, {0, 1}, {1, 0}, {1, 2}, {1, 1}, {3, 1} };
#elif CUBE_LAYOUT == VERTICAL
    static int face_offset[6][2] = { {2, 1}, {0, 1}, {1, 0}, {1, 2}, {1, 1}, {1, 3} };
#endif
    static int face_flags[6] = {
        DDSCAPS2_CUBEMAP_POSITIVEX,
        DDSCAPS2_CUBEMAP_NEGATIVEX,
        DDSCAPS2_CUBEMAP_POSITIVEY,
        DDSCAPS2_CUBEMAP_NEGATIVEY,
        DDSCAPS2_CUBEMAP_POSITIVEZ,
        DDSCAPS2_CUBEMAP_NEGATIVEZ
    };

    // Load unwrapped cube map.
    static bool LoadCubeMap( QDataStream & s, const DDSHeader & header, QImage & img )
    {
        // Create dst image.
#if CUBE_LAYOUT == HORIZONTAL
        if( !img.create( 4 * header.width, 3 * header.height, 32 )) {
            return false;   // duplicate code for correct syntax coloring.
        }
#elif CUBE_LAYOUT == VERTICAL
        if( !img.create( 3 * header.width, 4 * header.height, 32 )) {
            return false;
        }
#endif

        DDSType type = GetType( header );
        
        // Enable alpha buffer for transparent or DDS images.
        if( HasAlpha( header ) || type >= DDS_DXT1 ) {
            img.setAlphaBuffer( true );
        }

        // Select texture loader.
        TextureLoader loader = GetTextureLoader( type );
        if( loader == NULL ) {
            return false;
        }

        // Clear background.
        img.fill( 0 );

        // Create face image.
        QImage face;
        if( !face.create( header.width, header.height, 32 )) {
            return false;
        }
        
        int offset = s.device()->at();
        int size = FaceOffset( header );

        for( int i = 0; i < 6; i++ ) {

            if( !(header.caps.caps2 & face_flags[i]) ) {
                // Skip face.
                continue;
            }

            // Seek device.
            s.device()->at( offset );
            offset += size;

            // Load face from stream.
            if( !loader( s, header, face ) ) {
                return false;
            }

#if CUBE_LAYOUT == VERTICAL
            if( i == 5 ) {
                face = face.mirror(true, true);
            }
#endif

            // Compute face offsets.
            int offset_x = face_offset[i][0] * header.width;
            int offset_y = face_offset[i][1] * header.height;

            // Copy face on the image.
            for( uint y = 0; y < header.height; y++ ) {
                QRgb * src = (QRgb *) face.scanLine( y );
                QRgb * dst = (QRgb *) img.scanLine( y + offset_y ) + offset_x;
                memcpy( dst, src, sizeof(QRgb) * header.width );
            }
        }

        return true;
    }

}


KDE_EXPORT void kimgio_dds_read( QImageIO *io )
{
    QDataStream s( io->ioDevice() );
    s.setByteOrder( QDataStream::LittleEndian );

    // Validate header.
    uint fourcc;
    s >> fourcc;
    if( fourcc != FOURCC_DDS ) {
        kdDebug(399) << "This is not a DDS file." << endl;
        io->setImage( 0 );
        io->setStatus( -1 );
        return;
    }

    // Read image header.
    DDSHeader header;
    s >> header;

    // Check image file format.
    if( s.atEnd() || !IsValid( header ) ) {
        kdDebug(399) << "This DDS file is not valid." << endl;
        io->setImage( 0 );
        io->setStatus( -1 );
        return;
    }

    // Determine image type, by now, we only support 2d textures.
    if( !IsSupported( header ) ) {
        kdDebug(399) << "This DDS file is not supported." << endl;
        io->setImage( 0 );
        io->setStatus( -1 );
        return;
    }


    QImage img;
    bool result;

    if( IsCubeMap( header ) ) {
        result = LoadCubeMap( s, header, img );
    }
    else {
        result = LoadTexture( s, header, img );
    }

    if( result == false ) {
        kdDebug(399) << "Error loading DDS file." << endl;
        io->setImage( 0 );
        io->setStatus( -1 );
        return;
    }

    io->setImage( img );
    io->setStatus( 0 );
}


KDE_EXPORT void kimgio_dds_write( QImageIO * )
{
    // TODO Stub!
}

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