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libpbm - functions to read and write PBM image files
int pm_keymatch(char * str, char * keyword, int minchars);
int pm_maxvaltobits(int maxval);
int pm_bitstomaxval(int bits);
unsigned int pm_lcm(unsigned int x, unsigned int y, unsigned int z, unsigned int limit);
void pm_message(char * fmt, ... );
void pm_error(char * fmt, ... );
void pm_perror(char * fmt, ... );
void pm_usage(char * usage);
FILE *pm_openr(char * name)
FILE *pm_openw(char * name);
FILE *pm_openr_seekable(const char * name);
FILE *pm_close(FILE * fp);
char *pm_read_unknown_size(FILE * fp, long *nread);
unsigned int pm_tell(FILE * fileP);
void pm_seek(FILE * fileP, unsigned long filepos);
bit **pbm_allocarray(int cols, int rows);
bit *pbm_allocrow(int cols);
pbm_freearray(bit **bits, int rows);
pbm_freerow(bit *bitrow);
void pbm_readpbminit(FILE * fp, int *colsP, int *rowsP, int *formatP);
void pbm_readpbmrow(FILE * fp, bit *bitrow, int cols, int format);
void pbm_readpbmrow_packed(FILE *
fp,
unsigned char * const packed_bits,
const int cols,
const int format);
void bit** pbm_readpbm(FILE * fp, int *colsP, int *rowsP);
void pbm_writepbminit(FILE * fp, int cols, int rows, int forceplain);
void pbm_writepbmrow(FILE * fp, bit *bitrow, int cols, int forceplain);
void pbm_writepbmrow_packed(FILE *
fp,
unsigned char * const packed_bits,
const int cols,
const int forceplain);
void pbm_writepbm(FILE * fp, bit **bits, int cols, int rows, int forceplain);
#define pbm_packed_bytes(cols) ...
void pbm_nextimage( FILE *file, int * const eofP);
void pbm_check( FILE * file, const enum pm_check_type check_type, const int format, const int cols, const int rows, enum pm_check_code * const retval);
int pm_readbigshort(FILE *in, short *sP);
int pm_writebigshort(FILE *out, short s);
int pm_readbiglong(FILE *in, long *lP);
int pm_writebiglong(FILE *out, long l);
int pm_readlittleshort(FILE *in, short *sP);
int pm_writelittleshort(FILE *out, short s);
int pm_readlittlelong(FILE *in, long *lP);
int pm_writelittlelong(FILE *out, long l);
pm_lcm() computes the least common multiple of 3 integers. You also specify a limit and if the LCM would be higher than that limit, pm_lcm() just returns that limit.
pm_error() is a printf() style routine that writes an error message to the Standard Error file stream and exits the program with an exit code of 1.
pm_openr_seekable() appears to open the file just like pm_openr(), but the file thus opened is guaranteed to be seekable (you can use ftell() and fseek() on it). pm_openr_seekable() pulls this off by copying the entire file to a temporary file and giving you the handle of the temporary file, if it has to. If the file you name is a regular file, it's already seekable so pm_openr_seekable() just does the same thing as pm_openr(). But if it is, say, a pipe, it isn't seekable. So pm_openr_seekable() reads the pipe until EOF into a temporary file, then opens that temporary file and returns the handle of the temporary file. The temporary file is seekable.
The file pm_openr_seekable() creates is one that the operating system recognizes as temporary, so when you close the file, by any means, it gets deleted.
You need a seekable file if you intend to make multiple passes through the file. The only alternative is to read the entire image into memory and work from that copy. That may use too much memory. Note that the image takes less space in the file cache than in a buffer in memory. As much as 96 times less space! Each sample is an integer in the buffer, which is usually 96 bits. In the file, a sample may be as small as 1 bit and rarely more than 8 bits.
pm_read_unknown_size() reads an entire file or input stream of unknown size to a buffer. Allocate memory more memory as needed. The calling routine has to free the allocated buffer with free().
pm_read_unknown_size() returns a pointer to the allocated buffer. The nread argument returns the number of bytes read.
pm_tell() returns a handle for the current position of the file, whether it be the header or a row of the raster. Use the handle as an argument to pm_seek() to reposition the file there later. The file must be seekable (which you can ensure by opening it with pm_openr_seekable())orthismayfail.
pm_writebigshort(), pm_readbiglong(), pm_writebiglong(), pm_readlittleshort(), pm_writelittleshort(), pm_readlittlelong(), and pm_writelittlelong() are routines to read and write short and long ints in either big- or little-endian byte order. The return value is 0 upon success and -1 upon failure (either EOF or I/O error).
#define PBM_WHITE ...
#define PBM_BLACK ...
Each bit should contain only the values of PBM_WHITE or PBM_BLACK.
#define PBM_FORMAT ...
#define RPBM_FORMAT ...
#define PBM_TYPE PBM_FORMAT
#define PBM_FORMAT_TYPE(f) ...
These are for distinguishing different file formats and types.
pbm_readpbm() reads an entire bitmap file into memory, returning the allocated array and filling in the rows and cols variables. This function combines pbm_readpbminit(), pbm_allocarray() and pbm_readpbmrow().
pbm_writepbm() writes the header and all data for a PBM image to a PBM file. This function combines pbm_writepbminit() and pbm_writepbmrow().
pbm_nextimage() positions a PBM input file to the next image in it (so that a subsequent pbm_readpbminit() reads its header).
Immediately before a call to pbm_nextimage(), the file must be positioned either at its beginning (i.e. nothing has been read from the file yet) or just after an image (i.e. as left by a pbm_readpbmrow() of the last row in the image).
In effect, then, all pbm_nextimage() does is test whether there is a next image or the file is positioned at end-of-file.
If pbm_nextimage() successfully positions to the next image, it returns *eofP false (0). If there is no next image in the file, it returns *eofP true (1). If it can't position or determine the file status due to a file error, it issues an error message and exits the program with an error exit code.
pbm_check() checks for the common file integrity error where the file is the wrong size to contain all the image data. pbm_check() assumes the file is positioned after an image header (as if pbm_readpbminit() was the last operation on the file). It checks the file size to see if the number of bytes left in the file are the number required to contain the image raster. If the file is too short, pbm_check() causes the program to exit with an error message and error completion code. Otherwise, it returns one of the following values (enumerations of the enum pm_check_code type) as *retval:
check_type must have the value PM_CHECK_BASIC (an enumerated value of the pm_check_type enumerated type). Otherwise, the effect of pbm_check() is unpredictable. This argument exists for future backward compatible expansion of the function of pbm_check().
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