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convgltex.cpp

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#include "Teddy/TeddyConfig.h"
#include <SDL.h>
#ifdef HAVE_LIB_SDL_IMAGE
#   include <SDL_image.h>
#endif
#include <cstring>


SDL_Surface *conv_surf_gl( SDL_Surface *s, int want_alpha ){
    Uint32       rmask;
    Uint32       gmask;
    Uint32       bmask;
    Uint32       amask;
    SDL_Surface *conv;
    int          bpp = want_alpha ? 32 : 24;

    //  SDL interprets each pixel as a 24 or 32-bit number, so our
    //  masks must depend on the endianness (byte order) of the
    //  machine.
#if SDL_BYTEORDER == SDL_BIG_ENDIAN
    rmask = 0xff000000 >> (32 - bpp);
    gmask = 0x00ff0000 >> (32 - bpp);
    bmask = 0x0000ff00 >> (32 - bpp);
    amask = 0x000000ff >> (32 - bpp);
#else
    rmask = 0x000000ff;
    gmask = 0x0000ff00;
    bmask = 0x00ff0000;
    amask = want_alpha ? 0xff000000 : 0;
#endif

    //  Check if the surface happens to be in the right format
    if(
        (s->format->BitsPerPixel == bpp  ) &&
        (s->format->Rmask        == rmask) &&
        (s->format->Gmask        == gmask) &&
        (s->format->Bmask        == bmask) &&
        (s->format->Amask        == amask) &&
        !(s->flags & SDL_SRCCOLORKEY) )
    {
        //  No conversion needed
        return s;
    }

    //  Wrong format, conversion necessary

    //  SDL surfaces are created with lines padded to start at 32-bit boundaries
    //  which suits OpenGL well (as long as GL_UNPACK_ALIGNMENT remains
    //  unchanged from its initial value of 4)
    conv = SDL_CreateRGBSurface(
        SDL_SWSURFACE, 
        s->w, 
        s->h, 
        bpp,
        rmask, 
        gmask, 
        bmask, 
        amask
    );
    if( !conv ){
        SDL_FreeSurface( conv );
        return NULL;
    }

    //  SDL sets the SDL_SRCALPHA flag on all surfaces with an
    //  alpha channel. We need to clear that flag for the copy,
    //  since SDL would attempt to alpha-blend our image otherwise */
    if( want_alpha ){
        SDL_SetAlpha( s, 0, 255 );
    }

    //  Do the conversion. If the source surface has a colourkey, then it
    //  will be used in the blit. We use the fact that newly created software
    //  surfaces are zero-filled, so the pixels not blitted will remain
    //  transparent.
    if( SDL_BlitSurface(s,NULL,conv,NULL) < 0 ){
        //  Blit error
        SDL_FreeSurface( conv );
        conv = NULL;
    }

    //tksuoran: This causes to crash with some images
    //SDL_FreeSurface(s);

    return conv;
}


SDL_Surface *load_gl_texture( const char *file ){
#ifdef HAVE_LIB_SDL_IMAGE
    SDL_Surface *s = IMG_Load(file);
#else
    SDL_Surface *s = NULL;
#endif
    if( s==NULL ){
        return NULL;
    }
    return conv_surf_gl(s, s->format->Amask || (s->flags & SDL_SRCCOLORKEY));
}