7. Texture example (client side)

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  // Array of texels, dynamically populated fom an image file:
  GLubyte* image_data;                     // Raw color information from a file
  /* Load image data... (not shown) */
  glEnable( GL_TEXTURE_2D );               // Turn on texturing
  // Create a single texture object:
  glGenTextures( 1, &tex_buffer_ID );            // Create an ID for a texture buffer
  glBindTexture( GL_TEXTURE_2D, tex_buffer_ID ); // Bind texture buffer to GL_TEXTURE_2D target
  glTexImage2D( // allocate storage for the texture and pass data to the texture buffer
      GL_TEXTURE_2D, 0, GL_RGB, bmpWidth, bmpHeight, 0, GL_BGR, GL_UNSIGNED_BYTE, image_data );
  /*  |              |  |                            |  |       |                 |
      |              |  |                            |  |       |                 Raw data
      |              |  |                            |  |       C++ client pixel data type
      |              |  |                            |  C++ client pixel data format
      |              |  |                            must be 0, no longer used
      |              |  internal format, the number of color components in the texture
      |              mipmapping level: 0 is the base image level
      target texture type */
  tex_coord_ID = glGetAttribLocation( shader_program_ID, "s_vTexCoord" );
  glEnableVertexAttribArray( tex_coord_ID );
  int texture_coord_offset = 6*NUM_VERTICES*sizeof( GLfloat ); // see example/Lecture17_Texture for details
  glVertexAttribPointer(
      tex_coord_ID, 2, GL_FLOAT, GL_FALSE, 0, BUFFER_OFFSET( texture_coord_offset ) );
  
  // Set the preferences:
  glTexParameterf( GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_MIRRORED_REPEAT );
  glTexParameterf( GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_MIRRORED_REPEAT );
  glTexParameterf( GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST );
  glTexParameterf( GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST );
  
  texture_ID = glGetUniformLocation( shader_program_ID, "texture" );
  const int TEXTURE_UNIT_ZERO = 0;
  // First, activate texture unit (relative to GL_TEXTURE0)
  glActiveTexture( GL_TEXTURE0 + TEXTURE_UNIT_ZERO );
  // Second, tell "texture" sampler to use the 0th texture unit:
  glUniform1i( texture_ID, TEXTURE_UNIT_ZERO );