source: orxonox.OLD/orxonox/branches/particleEngine/src/lib/graphics/importer/texture.cc @ 3947

/* 
   orxonox - the future of 3D-vertical-scrollers

   Copyright (C) 2004 orx

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

   ### File Specific:
   main-programmer: Benjamin Grauer
   co-programmer: ...
*/

#define DEBUG_SPECIAL_MODULE DEBUG_MODULE_IMPORTER

#include "texture.h"

#include "graphics_engine.h"

/**
   \brief Constructor for a Texture
*/
Texture::Texture(const char* imageName)
{
  this->texture = 0;
  if (imageName)
    this->loadImage(imageName);
}  

/**
   \brief Destructor of a Texture
   
   Frees Data, and deletes the textures from GL
*/
Texture::~Texture(void)
{
  if (this->texture)
    glDeleteTextures(1, &this->texture);
}

/**
   \brief a Simple function that switches two char values
   \param a The first value
   \param b The second value
*/
void Texture::swap (unsigned char &a, unsigned char &b)
{
  unsigned char temp;
  temp = a;
  a    = b;
  b    = temp;
}


/**
   \brief Loads a Texture to the openGL-environment.
   \param surface the Image to load to openGL
   \returns The ID of the texture.
*/
GLuint Texture::loadTexToGL (SDL_Surface* surface)
{
  if (GraphicsEngine::texturesEnabled)
    {
      PRINTF(4)("Loading texture to OpenGL-Environment.\n");

      GLuint texture;
      int w, h;
      SDL_Surface *image;
      SDL_Rect area;
      Uint32 saved_flags;
      Uint8  saved_alpha;
      
      w = surface->w;
      h = surface->h;
      
      image = SDL_CreateRGBSurface(SDL_SWSURFACE,
                                   w, h,
                                   32,
#if SDL_BYTEORDER == SDL_LIL_ENDIAN /* OpenGL RGBA masks */
                                   0x000000FF, 
                                   0x0000FF00, 
                                   0x00FF0000, 
                                   0xFF000000
#else
                                   0xFF000000,
                                   0x00FF0000, 
                                   0x0000FF00, 
                                   0x000000FF
#endif
                                   );
      if ( image == NULL ) {
        return 0;
      }
      
      /* Save the alpha blending attributes */
      saved_flags = surface->flags&(SDL_SRCALPHA|SDL_RLEACCELOK);
      saved_alpha = surface->format->alpha;
      if ( (saved_flags & SDL_SRCALPHA) == SDL_SRCALPHA ) {
        SDL_SetAlpha(surface, 0, 0);
      }
      
      /* Copy the surface into the GL texture image */
      area.x = 0;
      area.y = 0;
      area.w = surface->w;
      area.h = surface->h;
      SDL_BlitSurface(surface, &area, image, &area);
      
      /* Restore the alpha blending attributes */
      if ( (saved_flags & SDL_SRCALPHA) == SDL_SRCALPHA ) {
        SDL_SetAlpha(surface, saved_flags | SDL_OPENGL, saved_alpha);
      }
      
      /* Create an OpenGL texture for the image */
      glGenTextures(1, &texture);
      glBindTexture(GL_TEXTURE_2D, texture);
      glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
      glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
      // build the Texture
      glTexImage2D(GL_TEXTURE_2D,
                   0,
                   GL_RGBA,
                   w, h,
                   0,
                   GL_RGBA,
                   GL_UNSIGNED_BYTE,
                   image->pixels);
      // build the MipMaps
      gluBuild2DMipmaps(GL_TEXTURE_2D,
                        GL_RGBA,
                        w,
                        h,
                        GL_RGBA,
                        GL_UNSIGNED_BYTE,
                        image->pixels);
      
      SDL_FreeSurface(image); /* No longer needed */
      
      return texture;
    }
}

/**
   \brief loads an Image from a file to a Texture
   \param imageName The image to load
*/
bool Texture::loadImage(const char* imageName)
{
  if (GraphicsEngine::texturesEnabled)
    {
      if (imageName)
        {
          SDL_Surface* tmpSurf;
          if (this->texture)
            glDeleteTextures(1, &this->texture);
          // load the new Image to memory
          tmpSurf = IMG_Load(imageName);
          if(!tmpSurf)
            {
              PRINTF(1)("IMG_Load: %s\n", IMG_GetError());
              return false;
            }

          GLubyte* pixels = (GLubyte*)tmpSurf->pixels;
          
          /* this swaps the Mapping so lowel left will be upper left */
          for( int i = 0 ; i < (tmpSurf->h / 2) ; ++i )
            for( int j = 0 ; j < tmpSurf->w * tmpSurf->format->BytesPerPixel; j += tmpSurf->format->BytesPerPixel )
              for(int k = 0; k < tmpSurf->format->BytesPerPixel; ++k)
                swap( pixels[(i * tmpSurf->w * tmpSurf->format->BytesPerPixel) + j + k],
                      pixels[ ( (tmpSurf->h - i - 1) * tmpSurf->w *  tmpSurf->format->BytesPerPixel) + j + k]);

          PRINTF(3)("loading Image %s\n", imageName);
          if (tmpSurf)
            this->texture = loadTexToGL(tmpSurf);

          
          SDL_FreeSurface(tmpSurf);
          return true;
        }
      else
        {
          PRINTF(2)("Image not Found: %s\n", imageName);
          return false;
        }
    }
}