libppm - functions to support portable pixmap programs


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



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 ...
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.


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.


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().


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().


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.


pbm(3), pgm(3)


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