int i4_max ( int i1, int i2 );

bool ppmb_check_data ( int xsize, int ysize, int maxrgb, unsigned char *r,
  unsigned char *g, unsigned char *b );

bool ppmb_example ( int xsize, int ysize, unsigned char *r, 
  unsigned char *g, unsigned char *b );

bool ppmb_read ( char *file_in_name, int *xsize, int *ysize, int *maxrgb,
  unsigned char **r, unsigned char **g, unsigned char **b );
bool ppmb_read_data ( ifstream &file_in, int xsize, int ysize, unsigned char *r,
  unsigned char *g, unsigned char *b );
bool ppmb_read_header ( ifstream &file_in, int *xsize, int *ysize, int *maxrgb );
bool ppmb_read_test ( char *file_in_name );

bool ppmb_write ( char *file_out_name, int xsize, int ysize, unsigned char *r,
  unsigned char *g, unsigned char *b );
bool ppmb_write_data ( ofstream &file_out, int xsize, int ysize, unsigned char *r,
  unsigned char *g, unsigned char *b );
bool ppmb_write_header ( ofstream &file_out, int xsize, int ysize, int maxrgb );
bool ppmb_write_test ( char *file_out_name );