text: /* ppm.h - header file for libppm portable pixmap library
  */
  
  #ifndef _PPM_H_
  #define _PPM_H_
  
  #include "pgm.h"
  
  typedef gray pixval;
  
  #ifdef PPM_PACKCOLORS
  
  #define PPM_MAXMAXVAL 1023
  typedef unsigned long pixel;
  #define PPM_GETR(p) (((p) & 0x3ff00000) >> 20)
  #define PPM_GETG(p) (((p) & 0xffc00) >> 10)
  #define PPM_GETB(p) ((p) & 0x3ff)
  #define PPM_ASSIGN(p,red,grn,blu) (p) = ((pixel) (red) << 20) | ((pixel) (grn) << 10) | (pixel) (blu)
  #define PPM_EQUAL(p,q) ((p) == (q))
  
  #else /*PPM_PACKCOLORS*/
  
  #define PPM_MAXMAXVAL PGM_MAXMAXVAL
  typedef struct
      {
      pixval r, g, b;
      } pixel;
  #define PPM_GETR(p) ((p).r)
  #define PPM_GETG(p) ((p).g)
  #define PPM_GETB(p) ((p).b)
  #define PPM_ASSIGN(p,red,grn,blu) do { (p).r = (red); (p).g = (grn); (p).b = (blu); } while ( 0 )
  #define PPM_EQUAL(p,q) ( (p).r == (q).r && (p).g == (q).g && (p).b == (q).b )
  
  #endif /*PPM_PACKCOLORS*/
  
  
  /* Magic constants. */
  
  #define PPM_MAGIC1 'P'
  #define PPM_MAGIC2 '3'
  #define RPPM_MAGIC2 '6'
  #define PPM_FORMAT (PPM_MAGIC1 * 256 + PPM_MAGIC2)
  #define RPPM_FORMAT (PPM_MAGIC1 * 256 + RPPM_MAGIC2)
  #define PPM_TYPE PPM_FORMAT
  
  
  /* Macro for turning a format number into a type number. */
  
  #define PPM_FORMAT_TYPE(f) ((f) == PPM_FORMAT || (f) == RPPM_FORMAT ? PPM_TYPE : PGM_FORMAT_TYPE(f))
  
  
  /* Declarations of routines. */
  
  void ppm_init ARGS(( int* argcP, char* argv[] ));
  
  #define ppm_allocarray( cols, rows ) ((pixel**) pm_allocarray( cols, rows, sizeof(pixel) ))
  #define ppm_allocrow( cols ) ((pixel*) pm_allocrow( cols, sizeof(pixel) ))
  #define ppm_freearray( pixels, rows ) pm_freearray( (char**) pixels, rows )
  #define ppm_freerow( pixelrow ) pm_freerow( (char*) pixelrow )
  
  pixel** ppm_readppm ARGS(( FILE* file, int* colsP, int* rowsP, pixval* maxvalP ));
  void ppm_readppminit ARGS(( FILE* file, int* colsP, int* rowsP, pixval* maxvalP, int* formatP ));
  void ppm_readppmrow ARGS(( FILE* file, pixel* pixelrow, int cols, pixval maxval, int format ));
  
  void ppm_writeppm ARGS(( FILE* file, pixel** pixels, int cols, int rows, pixval maxval, int forceplain ));
  void ppm_writeppminit ARGS(( FILE* file, int cols, int rows, pixval maxval, int forceplain ));
  void ppm_writeppmrow ARGS(( FILE* file, pixel* pixelrow, int cols, pixval maxval, int forceplain ));
  
  pixel ppm_parsecolor ARGS(( char* colorname, pixval maxval ));
  char* ppm_colorname ARGS(( pixel* colorP, pixval maxval, int hexok ));
  
  extern pixval ppm_pbmmaxval;
  /* This is the maxval used when a PPM program reads a PBM file.  Normally
  ** it is 1; however, for some programs, a larger value gives better results
  */
  
  
  /* Color scaling macro -- to make writing ppmtowhatever easier. */
  
  #define PPM_DEPTH(newp,p,oldmaxval,newmaxval) \
      PPM_ASSIGN( (newp), \
  	( (int) PPM_GETR(p) * (newmaxval) + (oldmaxval) / 2 ) / (oldmaxval), \
  	( (int) PPM_GETG(p) * (newmaxval) + (oldmaxval) / 2 ) / (oldmaxval), \
  	( (int) PPM_GETB(p) * (newmaxval) + (oldmaxval) / 2 ) / (oldmaxval) )
  
  
  /* Luminance macro. */
  
  #define PPM_LUMIN(p) ( 0.299 * PPM_GETR(p) + 0.587 * PPM_GETG(p) + 0.114 * PPM_GETB(p) )
  
  #endif /*_PPM_H_*/
  