libppm(3)                                               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 maximum 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  combines   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 force-
       plain 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_writeppm-
       row().

   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 dec-
       imal  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  colorspec  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.

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