📄 faxcom.txt
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*****************************************************
**** ****
**** Faxdecod.c ****
**** ****
*****************************************************
/***************************************************************************
Faxdecoder : Usage faxdecoder <compressed_fax >uncompressed.fax
This program compresses a fax using a model based on an order 16 model.
Context is as follows : C = Context bits, P = bit being predicted
x
xxxxxx
xxxxxx
xxxP
Variable names beginning with capital letters are arithmetic coding
variables used by the arithmetic coding routines.
-------------------------------
Copyright Raymond P. Wilson 1989.
This program is a shareware program. If you use it then credit must be
given to the author (me). If you find this program useful please send
whatever you think it is worth ($25 is suggested) to :
Raymond P. Wilson
38 Paremata St
Atawhai
Nelson
New Zealand
**************************************************************************/
#include <stdio.h>
#include <sys/time.h>
#include <sys/resource.h>
#include "coderdef.i" /* My faxcoder definitions etc... */
#include "arithdec.i" /* Arithmetic decoding functions and defs ... */
/*************************************************************************
Function : Initialise_model
Parameters : None
Returns : Nothing
Initialise_model sets up all the structures and initialisation
required by the fax coder.
************************************************************************/
void initialise_model()
{
int i;
/* Initialise context bits and saved context arrays */
for (i = 0;i < CONTEXT_WINDOW_BPL;i++)
saved[i] = 0;
/* Initialise context information array */
for (i = 0;i < NUM_CONTEXTS;i++)
{
contexts[i].zero_count = 1;
contexts[i].sum = 2; /* No explicit count of ones is kept */
} /* as this is implicit in the sum */
}
/************************************************************************
Function : Decompress
Parameters : None
Returns : Nothing
Decompress decompresses a fax file read in from std input.
***********************************************************************/
void decompress()
{
register codevalue S_low=0, S_high=0;
/* Arithmetic decoder vars high and low of range */
register int
context, /* Context at predicted bit */
bitnum, /* Bit being compressed on current line */
S_bitstogo, /* Arithmetic decoder var - used in inputting bits */
H = half, /* Arithmetic decoder var - contains constant half */
last, /* Shifting three bit field of last three bits read in */
bitsleft = 8, /* Mask for getting bit out of byte */
byte = 0; /* Byte read in from */
startinputingbits();
startdecoding();
for (line = 0;line < NUM_LINES;line++)
{
last = 0; /* Clear shifting temporary storage for incoming bits */
/* Start iterating over bits in line - start in from edge of 'sheet'
to give white space at edge for context */
for (bitnum = CONTEXT_SIDE_BITS;
bitnum < (CONTEXT_SIDE_BITS + BITS_PER_LINE);bitnum++)
{
/* Work out context that precedes bit being predicted */
context = saved[bitnum] | (last >> 3);
/* Store that part of the context that will be used on the next line */
saved[bitnum] = (context & CONTEXT_MASK) << 6;
/* Decode the bit currently being decompressed and update the model */
/* Call arithmetic_decode_target to get position in range */
if (arithmetic_decode_target(contexts[context].sum)
< contexts[context].zero_count)
{
/* Decode a zero bit */
arithmetic_decode_zero(contexts[context].zero_count,
contexts[context].sum);
contexts[context].zero_count++; /* Increment zero bit count */
write_decoded0; /* Output a decoded zero */
/* Add a zero bit to shifting storage and add this to previously
stored context from two bits back */
saved[bitnum-2] |= (last = (last << 1) & 0x38);
}
else
{
/* 'Decode' a one bit */
arithmetic_decode_one(contexts[context].zero_count,
contexts[context].sum);
write_decoded1; /* Write out a decoded ont bit */
/* Add a zero bit to shifting storage and add this to previously
stored context from two bits back */
saved[bitnum-2] |= (last = ((last << 1) | 0x8) & 0x38);
}
/* Increment sum count and check to see if counts need halving */
if ((++contexts[context].sum) == HALVE_LIMIT)
{
contexts[context].zero_count = (contexts[context].zero_count >> 2) + 1;
contexts[context].sum = (contexts[context].sum >> 2) + 2;
}
}
}
}
/*************************************************************************
Main program.
************************************************************************/
main(argc,argv)
int argc;
char **argv;
{
initialise_model();
fprintf(stderr,"Decompressing file, please wait.\n");
start_time = get_time(); /* Get starting time */
decompress();
total_time = get_time() - start_time; /* Get total time from difference */
fprintf(stderr,"%s: Decompressed fax in %.3f seconds.\n",argv[0],total_time);
exit(0);
}
*****************************************************
**** ****
**** Faxcoder.c ****
**** ****
*****************************************************
/***************************************************************************
Faxcoder : Usage faxcoder <fax_file.fax >output
This program compresses a fax using a model based on an order 16 model.
Context is as follows : x = Context bits, P = bit being predicted
x
xxxxxx
xxxxxx
xxxP
Variable names beginning with capital letters are arithmetic coding
variables used by the arithmetic coding routines.
-------------------------------
Copyright Raymond P. Wilson 1989.
This program is a shareware program. If you use it then credit must be
given to the author (me). If you find this program useful please send
whatever you think it is worth ($25 is suggested) to :
Raymond P. Wilson
38 Paremata St
Atawhai
Nelson
New Zealand
If you want to use this or parts of this program in a commercial product
then the authors permission is required.
**************************************************************************/
#include <stdio.h>
#include <sys/time.h>
#include <sys/resource.h>
#include "coderdef.i" /* My faxcoder definitions etc... */
#include "arithcod.i" /* Arithmetic coding functions and defs... */
/*************************************************************************
Function : Initialise_model
Parameters : None
Returns : Nothing
Initialise_model sets up all the structures and initialisation
required by the fax coder.
************************************************************************/
void initialise_model()
{
int i;
/* Initialise context bits and saved context arrays */
for (i = 0;i < CONTEXT_WINDOW_BPL;i++)
saved[i] = 0;
/* Initialise context information array */
for (i = 0;i < NUM_CONTEXTS;i++)
{
contexts[i].zero_count = 1;
contexts[i].sum = 2;
}
}
/************************************************************************
Function : Compress
Parameters : None
Returns : Nothing
Compress compresses a fax file read in from std input.
***********************************************************************/
void compress()
{
register codevalue S_low=0, S_high=0;
/* Arithmetic coder vars high and low of range */
register int
context, /* Context at predicted bit */
bitnum, /* Bit being compressed on current line */
S_bitstogo, /* Arithmetic coder var - used in inputting bits */
H = half, /* Arithmetic coder var - contains constant half */
last, /* Shifting three bit field of last three bits read in */
mask = 0, /* Mask for getting bit out of byte */
byte = 0; /* Byte read in from */
startoutputingbits();
startencoding();
for (line = 0;line < NUM_LINES;line++)
{
last = 0; /* Clear shifting temporary storage for incoming bits */
/* Start iterating over bits in line - start in from edge of 'sheet'
to give white space at edge for context */
for (bitnum = CONTEXT_SIDE_BITS;
bitnum < (CONTEXT_SIDE_BITS + BITS_PER_LINE);bitnum++)
{
/* Work out context that precedes bit being predicted */
context = saved[bitnum] | (last >> 3);
/* Store that part of the context that will be used on to the next line */
saved[bitnum] = (context & CONTEXT_MASK) << 6;
/* Get the bit that is to be compressed */
getabit()
/* Code the bit currently being compressed and update the model */
if (byte & mask)
{
arithmetic_encode_one(contexts[context].zero_count,
contexts[context].sum)
/* Add a one bit to shifting storage and add this to previously
stored context from two bits back */
saved[bitnum-2] |= (last = ((last << 1) | 0x8) & 0x38);
}
else
{
arithmetic_encode_zero(contexts[context].zero_count,
contexts[context].sum);
/* Add a zero bit to shifting storage and add this to previously
stored context from two bits back */
saved[bitnum-2] |= (last = (last << 1) & 0x38);
contexts[context].zero_count++; /* Increment zero bit count */
}
/* Increment sum count and check to see if counts need halving */
if ((++contexts[context].sum) == HALVE_LIMIT)
{
contexts[context].zero_count = (contexts[context].zero_count >> 2) + 1;
contexts[context].sum = (contexts[context].sum >> 2) + 2;
}
}
}
/* Finish up encoding and finishing outputting bits */
doneencoding();
doneoutputingbits();
}
/*************************************************************************
Main program.
************************************************************************/
main(argc, argv)
int argc;
char **argv;
{
initialise_model();
fprintf(stderr,"Compressing file, please wait...\n\n");
start_time = get_time(); /* Get starting time */
compress();
total_time = get_time() - start_time; /* Get total time from difference */
fprintf(stderr,"%s: compression %4.2f bpc (%4.2f : 1) in %.3f seconds.\n",
argv[0], (8 * cmpbytes)/(double)FAX_SIZE,
FAX_SIZE/(float)cmpbytes, total_time);
exit(0);
}
*****************************************************
**** ****
**** Coderdef.i ****
**** ****
*****************************************************
/*********************************************************************
FAXCOM Copyright Raymond P. Wilson 1989.
This program is a shareware program. If you use it then credit must be
given to the author (me). If you find this program useful please send
($25 is suggested) or whatever you think it is worth to :
Raymond P. Wilson
38 Paremata St
Atawhai
Nelson
New Zealand
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