libppm(3)         Image Format Library C++ Reference Manual          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 PPMMAXMAXVAL.  ppmpbmmaxval 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.




                                                                        Page 1

libppm(3)         Image Format Library C++ Reference Manual          libppm(3)



   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 ppmallocarray() 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 ppmreadppminit().

     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
     ppmreadppminit(), ppmallocarray() and ppmreadppmrow().

   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 ppmwriteppminit() and ppmwriteppmrow().






                                                                        Page 2

libppm(3)         Image Format Library C++ Reference Manual          libppm(3)



   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
     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.
































                                                                        Page 3