src/cgltexture.cpp

   1 #include "cgltexture.h"
   2
   3 CglTexture::CglTexture(std::string name)
   4 {
   5
   6 GLuint texture;         // This is a handle to our texture object
   7 SDL_Surface *surface;   // This surface will tell us the details of the image
   8 GLenum texture_format;
   9 GLint  nOfColors;
  10
  11 std::string filename = name + ".bmp";
  12 surface = SDL_LoadBMP( filename.c_str() );
  13 if ( surface ) {
  14
  15         // Check that the image's width is a power of 2
  16         if ( (surface->w & (surface->w - 1)) != 0 ) {
  17                 throw std::runtime_error(filename + "'s width is not a power of 2");
  18         }
  19
  20         // Also check if the height is a power of 2
  21         if ( (surface->h & (surface->h - 1)) != 0 ) {
  22                 throw std::runtime_error(filename + "'s height is not a power of 2");
  23         }
  24
  25         // get the number of channels in the SDL surface
  26         nOfColors = surface->format->BytesPerPixel;
  27         if (nOfColors == 4)     // contains an alpha channel
  28         {
  29                 if (surface->format->Rmask == 0x000000ff)
  30                         texture_format = GL_RGBA;
  31                 else
  32                         texture_format = GL_BGRA;
  33         } else if (nOfColors == 3)     // no alpha channel
  34         {
  35                 if (surface->format->Rmask == 0x000000ff)
  36                         texture_format = GL_RGB;
  37                 else
  38                         texture_format = GL_BGR;
  39         } else {
  40                 // this error should not go unhandled
  41                 throw std::runtime_error(filename + ": the image is not truecolor");
  42         }
  43
  44         // Have OpenGL generate a texture object handle for us
  45         glGenTextures( 1, &texture );
  46
  47         // Bind the texture object
  48         glBindTexture( GL_TEXTURE_2D, texture );
  49
  50         // Set the texture's stretching properties
  51         glTexParameteri( GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR );
  52         glTexParameteri( GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR );
  53
  54         // Edit the texture object's image data using the information SDL_Surface gives us
  55         glTexImage2D( GL_TEXTURE_2D, 0, nOfColors, surface->w, surface->h, 0,
  56                       texture_format, GL_UNSIGNED_BYTE, surface->pixels );
  57 } else {
  58         throw std::runtime_error("could not load " + filename);
  59 }
  60
  61 // Free the SDL_Surface only if it was successfully created
  62 if ( surface ) {
  63         SDL_FreeSurface( surface );
  64 }
  65
  66 }
  67
  68
  69 CglTexture::~CglTexture()
  70 {
  71 }