* @param filename name of file
* @param win_width width of our opengl window
* @param win_height height of our opengl window
* @param filename name of file
* @param win_width width of our opengl window
* @param win_height height of our opengl window
*/
bool sg_glWritePPMFile( const char *filename, GLubyte *buffer, int win_width,
int win_height, int mode);
*/
bool sg_glWritePPMFile( const char *filename, GLubyte *buffer, int win_width,
int win_height, int mode);