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sdl_image.cpp

//FILE:         sdl_image.cpp
//AUTHOR:       Nathan Cournia <nathan@cournia.com>

#include "sdl_image.h"

#ifdef HAVE_SDL
#ifdef HAVE_SDL_IMAGE

image::image_t*
image::sdl::load( const std::string& filename )
{
        //let SDL_image load the image
        SDL_Surface *surface = IMG_Load( filename.c_str( ) );

        //was the load successful
        if( surface ) {
                //conver SDL_Suface to image_t
                image_t *img = load( surface );
                
                //delete SDL_Surface
                SDL_FreeSurface( surface );
                return img;
        } else {
                //could not load image
                return NULL;
        }
}
#endif

//most the code below is in public domain
image::image_t*
image::sdl::load( SDL_Surface *surface )
{
        //sanity check
        assert( surface );
        
        //create a SDL surface that is easy to read from
        SDL_Surface *image = SDL_CreateRGBSurface( SDL_SWSURFACE, surface->w, 
        surface->h, 32,
#if SDL_BYTEORDER == SDL_LIL_ENDIAN 
                0x000000FF, 
                0x0000FF00, 
                0x00FF0000, 
                0xFF000000
#else
                0xFF000000,
                0x00FF0000, 
                0x0000FF00, 
                0x000000FF
#endif
        );

        //was the new surface created
        if ( image == NULL ) {
                return NULL;
        }

        //save alpha
        Uint32 saved_flags = surface->flags & (SDL_SRCALPHA | SDL_RLEACCELOK);
        Uint8 saved_alpha = surface->format->alpha;
        if ( (saved_flags & SDL_SRCALPHA) == SDL_SRCALPHA ) {
                SDL_SetAlpha( surface, 0, 0 );
        }

        //copy image to new friendly format
        SDL_Rect area;
        area.x = 0;
        area.y = 0;
        area.w = surface->w;
        area.h = surface->h;
        SDL_BlitSurface( surface, &area, image, &area );

        //restore alpha
        if ( (saved_flags & SDL_SRCALPHA) == SDL_SRCALPHA ) {
                SDL_SetAlpha(surface, saved_flags, saved_alpha);
        }

        //copy the image to an image_t*
        image_t *img = new image_t( image->w, image->h, image_t::RGBA, image_t::BYTE );
        img->seek( 0, 0 );
        unsigned int pixels = image->w * image->h;
        char *channel = (char*)(image->pixels);
        char r, g, b, a;
        for( unsigned int i = 0; i < pixels; ++i ) {
                r = *(channel++);
                g = *(channel++);
                b = *(channel++);
                a = *(channel++);
                img->write( r, g, b, a);
        }
        
        //we no longer need image
        SDL_FreeSurface( image );

        //return new image
        return img;
}
#endif

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