libppm(3)

NAME

       libppm - functions to support portable pixmap programs

SYNOPSIS

       #include <ppm.h>
       cc ... libppm.a libpgm.a libpbm.a

DESCRIPTION

   TYPES AND CONSTANTS
       typedef ... pixel;
       typedef ... pixval;
       #define PPM_MAXMAXVAL ...
       extern pixval ppm_pbmmaxval;

       Each  pixel  contains  three pixvals, each of which should contain only
       the values between 0 and PPM_MAXMAXVAL.  ppm_pbmmaxval  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.

       #define PPM_FORMAT ...
       #define RPPM_FORMAT ...
       #define PPM_TYPE PPM_FORMAT
       int PPM_FORMAT_TYPE( int format )

       For distinguishing different file formats and types.

       pixval PPM_GETR( pixel p )
       pixval PPM_GETG( pixel p )
       pixval PPM_GETB( pixel p )

       These three macros retrieve the red, green or blue value from the given
       pixel.

       void PPM_ASSIGN( pixel p, pixval red, pixval grn, pixval blu )

       This macro assigns the given red, green and blue values to the pixel.

       int PPM_EQUAL( pixel p, pixel q )

       This macro checks two pixels for equality.

       void PPM_DEPTH( pixel newp, pixel p, pixval oldmaxval, pixval newmaxval )

       This macro scales the colors of pixel p according the old and new maxi-
       mum values and assigns the new values to newp.  It is intended to  make
       writing ppmtowhatever easier.

       float PPM_LUMIN( pixel p )

       This macro determines the luminance of the pixel p.

   MEMORY MANAGEMENT
       pixel** ppm_allocarray( int cols, int rows )

       Allocate an array of pixels.

       pixel* ppm_allocrow( int cols )

       Allocate a row of the given number of pixels.

       void ppm_freearray( pixel** pixels, int rows )

       Free  the  array  allocated  with ppm_allocarray() containing the given
       number of rows.

       void pbm_freerow( pixel* pixelrow )

       Free a row of pixels.

   READING PBM FILES
       void ppm_readppminit( FILE* fp, int* colsP, int* rowsP, pixval* maxvalP, int* formatP )

       Read the header from a PPM file, filling in the rows, cols, maxval  and
       format variables.

       void ppm_readppmrow( FILE* fp, pixel* pixelrow, int cols, pixval maxval, int format )

       Read a row of pixels into the pixelrow array.  Format, cols, and maxval
       were filled in by ppm_readppminit().

       pixel** ppm_readppm( FILE* fp, int* colsP, int* rowsP, pixval* maxvalP )

       Read an entire pixmap file into memory, returning the  allocated  array
       and filling in the rows, cols and maxval variables.  This function com-
       bines ppm_readppminit(), ppm_allocarray() and ppm_readppmrow().

   WRITING FILES
       void ppm_writeppminit( FILE* fp, int cols, int rows, pixval maxval, int forceplain )

       Write the header for a  portable  pixmap  file.   The  forceplain  flag
       forces  a  plain-format  file to be written, as opposed to a raw-format
       one.

       void ppm_writeppmrow( FILE* fp, pixel* pixelrow, int cols, pixval maxval, int forceplain )

       Write a row from a portable pixmap.

       void ppm_writeppm( FILE* fp, pixel** pixels, int cols, int rows, pixval maxval, int forceplain )

       Write the header and all data for a  portable  pixmap.   This  function
       combines ppm_writeppminit() and ppm_writeppmrow().

   COLOR NAMES
       pixel ppm_parsecolor( char* colorname, pixval maxval )

       Parses an ASCII color name into a pixel.  The color can be specified in
       three ways.  One, as a name, assuming that a pointer  to  an  X11-style
       color  names  file  was  compiled in.  Two, as an X11-style hexadecimal
       number: #rgb, #rrggbb,  #rrrgggbbb,  or  #rrrrggggbbbb.   Three,  as  a
       triplet   of  decimal  floating  point  numbers  separated  by  commas:
       r.r,g.g,b.b.

       char* ppm_colorname( pixel* colorP, pixval maxval, int hexok )

       Returns a pointer to a string describing the given color.  If  the  X11
       color names file is available and the color appears in it, that name is
       returned.  Otherwise, if the hexok flag is true then a hexadecimal col-
       orspec  is  returned; if hexok is false and the X11 color names file is
       available, then the closest matching color is returned; otherwise, it's
       an error.

SEE ALSO

       pbm(3), pgm(3)

AUTHOR

       Copyright (C) 1989, 1991 by Tony Hansen and Jef Poskanzer.

                                                                     libppm(3)