RFC 0809
UCL facsimile system
Pages: 99
Unclassified
Unclassified
Part 3 of 3 – Pages 60 to 99
DACOM(DEV) DACOM(DEV)
NAME
dacom - facsimile machine
SYNOPSIS
DCT faxinput
setdct("faxin", 0350, 0174750, 0174740,
faxii, faxin, faxini, &faxoutput);
DCT faxoutput
setdct("faxout", 0354, 0174752, 0174742,
faxoi, faxot, faxoti, &faxinput);
DESCRIPTION
The DACOM facsimile machine can read a document, creating
the corresponding image data blocks. It can also accept the
data of relevant format, printing the correponding image.
Each data block consists of 585 bits, and is stored in a
block of 74 bytes starting on a byte boundary. The final 7
bits of the last byte are not used and they are undefined.
The 585 bits in each block need to be read as a bit stream:
the bits in each byte run from the high orger end of the
byte to the low order end. The last 12 bits of the 585 bits
in each block consistute the CRC field whereby the block can
be validated.
There are two kinds of blocks: SETUP blocks and DATA blocks.
The first of block of an image data file should be a single
SETUP block. All following blocks in the file must be DATA
blocks. Note that the second block is a DATA block that con-
tains ZERO samples, i.e. a dummy data blocks. Form the third
block, the DATA blocks store the reall image data.
A standard dacom page contains about 1200 scan lines, each
of which has 1726 pels. One can choose
Appendix II: Task Controller and Task Processes
CCITT(FAX) CCITT(FAX)
NAME
ccitt - conversion between vector and CCITT T4 format
SYNOPSIS
ccitt() - a MOS task
command string (task name is defined as ccitt):
ccitt"<function>
DESCRIPTION
This routine operates as a MOS pipe task to convert the vec-
tors to CCITT T4 format or inversely.
The parameter function specifies what the task is to do.
value function
1c one-dimensional compression
1d one-dimensional decompression
2c[<k>] two-dimensional compression
2d two-dimensional decompression
Note k is the maximun number of lines to be coded two-
dimensionally before a one-dimensionally coded line is in-
serted. If k is omitted, the default value 2 is adopted.
SEE ALSO
vector(fax), t4(fax), fitter(fax)
CHECK(FAX) CHECK(FAX)
NAME
check - check the validity of a vector file.
SYNOPSIS
check() - a MOS task
command string (the task name is defined as check):
check"<function>,<width>,<height>,[<from>,<to>]
DESCRIPTION
This routine operates as a MOS pipe task checking the vali-
dity of the input vector file.
The number of lines to be checked is specified by the param-
eter height. If the height of the image is less than the
parameter, the actual height is printed. Thus, one can set
the parameter height to a big number in order to count the
number of lines of the input image.
The run lengths in each of these lines are accumulated and
the sum is compared with the parameter width.
These are the basic functions which are performed whenever
the task is invoked. However, there are several options one
can choose by setting the one-character parameter function.
value function
'n' basic function only
'c' print the count of each line
'l' print all lines
's' print the lines in the interval
specified by parameter from and to
DIAGNOSTICS
A bad line will be reported and it will cause the job abort-
ed.
SEE ALSO
vector(fax), getl(fax), fitter(fax)
CHOP(FAX) CHOP(FAX)
NAME
chop - extract a designated rectangular area from an image
SYNOPSIS
chop() - a MOS task
command string (task name is defined as chop):
chop"<x0>,<y0>,<x1>,<y1>
DESCRIPTION
This routine operates as a MOS pipe task extracting a desig-
nated rectangular area from an input image. Input and out-
put are image data files in the form of vectors.
The following diagram shows the coordinate system being
used. Note that the lengths are measured in number of pels.
(0, 0) width X
+-------------------------+---->
| |
| |
| (x0, y0) |
| +---------+ |
| | | |
| | | |
| | | |
| | | |
| | | |
| | | |
| | | |
| +---------+ |
| (x1, y1) |
| |
| |
| |
| |
height +-------------------------+
|
|
Y V
As can be seen in the diagram, the rectangular area to be
extracted is specified by the parameters x0, x1, y0, y1,
which are decimal strings.
BUGS
One has to make sure that
0 < x0 < width
0 < y0 < height
0 < x1 < width
0 < y1 < height
SEE ALSO
vector(fax), getl(fax), putl(fax), fitter(fax)
CLEAN(FAX) CLEAN(FAX)
NAME
clean - clean an image.
SYNOPSIS
clean() - a MOS task
command string (task name is defined as clean):
clean"<width>,<height>
DESCRIPTION
This routine operates as a MOS pipe task cleaning an image
by means of mask scanning. Input and output are image data
files in the form of vectors.
The width and height should be given as the parameters.
SEE ALSO
vector(fax), getl(fax), putl(fax), fitter(fax)
DECOMP(FAX) DECOMP(FAX)
NAME
decomp - decompress DACOM blocks
SYNOPSIS
decomp() - a MOS task
command string (task name is defined as decomp):
decomp
DESCRIPTION
This task takes DACOM blocks from the Clean and Simple in-
terface, and decompresses them into vector format. Then it
writes the vectors to the Clean and Simple interface.
SEE ALSO
dacom(dev), vector(fax), fitter(fax)
FAX(FAX) FAX(FAX)
NAME
fax - interface process for DACOM facsimile machine
SYNOPSIS
fax() - a MOS task
command string (task name is defined as fax):
fax"<function>
DESCRIPTION
This task uses the Clean and Simple interface to read or
write facsimile image data.
The one character parameter function specifies whether the
data is to be read or written. Character w is for writing.
In this case, 74 byte DACOM blocks contaning correct CRC
fields are expected. On the other hand, character r is for
reading. In this case, a document is read on the facsimile
machine, the DACOM blocks being created.
SEE ALSO
dacom(dev), fitter(fax)
FITTER(FAX) FITTER(FAX)
NAME
fitter - fit processes together to form a data pipe
SYNOPSIS
fitter() - the MOS task controller
DESCRIPTION
According to the command string typed on the console, fitter
links the specified processes together to form a task chain.
The name of the processes is the name given in the PCB. The
processes must communicate using the C+S interface. Only one
C+S interface is opened per process - data is pushed in with
a cswrite and pulled out with a csread. The fitter does not
inspect the data in any way but merely passes it from one
process to another.
The format of command string is:
A | B | C.
The fitter takes data from the process called A, write it to
the process called B, reads data from the process B and
write that data to the process C. Note that all middle
processes are both read and written, while the first one in
the list is only read from and the last in the list is only
written to.
A double quote is used as the separator between the task
name and the open parameter string, e.g.
A"500 | B"n,xyz | C,
where the strings '500' and 'n,xyz' are the open parameter
stings for tasks A and B, respectively. The parameter
stirng is passed to the corresponding task routine when the
csopen call returns.
DIAGNOSTICS
The command string containing undefined task will be reject-
ed.
SEE ALSO
csinit(fax), csopen(fax), csread(fax), cswrite(fax)
FS(FAX) FS(FAX)
NAME
fs - file system for use under MOS
SYNOPSIS
fs() - a MOS task
command string (task name is defined as fs):
fs"<funciton>,<file_name>
DESCRIPTION
This is a file system, based on the Double Density floppy
disk, for use under MOS. The fs task is used for manipulate
the files, managed by the file system. This task can only
appear at the first or last position on a command string. In
the former case, the file specified is to be read, while the
file is to be written in the latter case.
The <function> field contains only one character indicating
the function to be performed. The possible values are:
e - open an existing file (for reading).
c - open an existing file, and set the length
to zero (for rewriting).
a - append to an existing file.
If the capitals A, C, and E are used, the functions are the
same as described above but the specified file is created if
it does not exist.
BUGS
This task is for reading and writing only. As for the other
facilities, e.g. seek, delete, status and sync, one has to
use C+S interface directly.
Note that only 15 files are permitted per disk, only drive 0
is supported at present, and no hierarchical directory is
allowed.
SEE ALSO
aed62(dev), fitter(fax)
FTP(FAX) FTP(FAX)
NAME
ftp, pftp - NIFTP task processes
SYNOPSIS
ftp(), pftp() - MOS tasks
command string (task name is defined as ftp):
ftp"<function>,<code>,<user_name>,<password>,<file_name>;
<trasport_service_process>:<transport_service_parameters>
DESCRIPTION
These tasks are implementation of Network Independent File
Transfer Protocol (NIFTP) for LSIs under MOS. They employ a
transport service for communication with a remote host on
the network, where the same protocol must be supported. They
communicate with the user process and transport service
processes thourgh the Clean and Simple interface, so that
they can be used in a fitter command chain directly.
The code is available in two versions: ftp which is a P+Q
version supporting both server and intitiator and pftp which
is a P version working only as an initiator. Both of them
are capable of sending and receiving.
This implementation of NIFTP is just a subset of the proto-
col as its main purpose is to provided the facsimile system
with a data transmission mechanism. For the sake of simpli-
city, only the necessary facilities are included in the
module, while more complex facilities, such as data compres-
sion and error recovery are not implemented. The following
table shows the transfer control parameters being used.
Attribute Value Mod. Remarks
Mode of access 0001 EQ Creating a new file
8002 EQ Retrieving file
Codes - - Text file, any parity
1002 EQ Binary file
Format effector 0000 EQ No interpretation
Binary mapping 0008 EQ Default byte size
Max record size 00FC EQ Default record size
Transfer size 0400 LE Default transfer size
Facilities 0000 EQ Minimum service
The meanings of the parameters in the command string are
listed below:
function is the NIFTP function of our site. Any ASCII string
beginning
beginning with 't' means the file is to be transmitted to
the remote site. Otherwise, the file will be retrieved from
the remote site.
code specifies the type of the file to be transferred. Any
ASCII string beginning with 'b' means it is a binary file,
while others mean text file.
user_name is the login name of the server site.
password is the password of the server site.
file_name is the name of the file to be transmitted.
transport_service_process is the process name of the tran-
sport service to be used.
transport_service_parameters are the parameter string re-
quired by the transport service. They are network dependent
and specified by the corresponding transport service.
SEE ALSO
fitter(fax)
GRINNELL(FAX) GRINNELL(FAX)
NAME
grinnell - task to convert and display fax vector data
SYNOPSIS
grinnell() - a MOS task
command string (task name is defined as string):
grinnell"<x0>,<y0>,<x1>,<y1>,<mode>,<colour>
DESCRIPTION
This task takes the vector data from a Clean and Simple in-
terface and displays it on the Grinnell screen. The Grinnell
screen is viewed as an X-Y plane with (0,0) being the lower
left hand corner, (512, 0) being the lower right hand
corner, etc.
The parameters x0, y0, x1, y1 are decimal strings defining
the rectangular space on the screen where the image is to be
displayed. If the image is smaller than this area, it is ar-
tificially expanded to the size of this area. If the image
is larger than this area it is truncated to the size of the
area.
The colour field consists of any combination of the charac-
ters r,g or b to define the colours red, green and blue
respectively. For instance "gb" would write the image as
yellow.
The mode defines how the image is to be displayed. Any com-
bination of the characters r,a and z may be used, to the
following effect:
r = reverse image
a = additive image
z = zerowrite image.
There are three bit planes to define the three colours. Nor-
mally the bit planes corresponding to the selected colours
have either zero bits or one bits written to them depending
upon whether the image or the background is being written.
For zerowrite, all non-selected bit planes (i.e. colours)
are always set to zero, thus erasing any unselected colours
in the area. Additive mode means that in the selected colour
planes the new bits are ORed in, rather than just written.
Thus the image is added to. In reverse mode, the image writ-
ten as one bits is written as zero bits and the bits written
as zero bits are written as one bits, i.e. the bits are
flipped before being used.
SEE ALSO
grinnell(dev), vector(fax), fitter(fax)
MERGE(FAX) MERGE(FAX)
NAME
merge - merge two images together
SYNOPSIS
merge() - a MOS task
command string (task name is defined as merge):
merge"<file_name>,<action>,<x0>,<y0>,<x1>,<y1>
DESCRIPTION
This routine operates as a MOS pipe task merging two images
together to form the result image. Input and output are im-
age data files in the form of vectors.
One of the two input images is called background which is to
be copied directly. This is specified by the parameter
file_name. The image data of the back ground is read via a
'tunnel', maintained by this task. Another input image is
taken form the Clean and Simple interface managed by the
fitter. As shown in the following diagram, the position
where it is to be put on the background image is specified
by the parameters x0, y0, x1, y1, which are decimal strings.
This implies that the dimension of the image is x1 - x0 and
y1 -y0.
(0, 0) width X
+-------------------------+---->
| |
| (x0, y0) |
| +---------+ |
| | | |
| | | |
| | | |
| | | |
| | | |
| +---------+ |
| (x1, y1) |
| |
| |
| (back ground) |
height +-------------------------+
|
|
Y V
The parameter action indicates how the two images are
merged. If it set to 0, The second image is simply overlaid
on the back ground image. On the other hand any non-zero
value
MERGE(FAX) MERGE(FAX)
causes the second image to replace the specified area of the
back ground image.
BUGS
One has to make sure that
0 < x0 < width_of_back_ground
0 < y0 < height_of_back_ground
0 < x1 < width_of_back_ground
0 < y1 < height_of_back_ground
In addition, x0, y0, x1, y1 must be consistent with the di-
mension of the image
SEE ALSO
vector(fax), getl(fax), putl(fax), chop(fax), fitter(fax)
OD(FAX) OD(FAX)
NAME
od - dump the input data
SYNOPSIS
od() - a MOS task
command string (task name is defined as od):
od"<format>
DESCRIPTION
This routine operates as a MOS pipe task dumping the input
data in a selected format. The input data is taken from the
Clean and Simple interface.
The meanings of the one character parameter format are:
value format
'd' words in decimal
'o' words in octal
'c' bytes in ASCII
'b' bytes in octal
SEE ALSO
fitter(fax)
RECOMP(FAX) RECOMP(FAX)
NAME
recomp - compress the vectors to form the DACOM blocks
SYNOPSIS
recomp() - a MOS task
command string (task name is defined as recomp):
recomp
DESCRIPTION
This task takes vectors from the Clean and Simple interface,
and recompresses them into DACOM blocks. Then it writes the
blocks to the Clean and Simple interface.
SEE ALSO
dacom(dev), vector(fax), fitter(fax)
SCALE(FAX) SCALE(FAX)
NAME
scale - scale an image to a specified dimension
SYNOPSIS
scale() - a MOS task
command string (task name is defined as scale):
scale"<old_width>,<old_height>,<new_width>,<new_height>
DESCRIPTION
This routine operates as a MOS pipe task scaling the input
image to the specified dimension. Input and output are im-
age data files in the form of vectors.
The dimension of the input image is given by the parameters
old_width and old_height, while the dimension of the output
is specified by the parameters new_width and new_height.
SEE ALSO
vector(fax), getl(fax), putl(fax), fitter(fax)
STRING(FAX) STRING(FAX)
NAME
string - convert an ASCII string to the vector format
SYNOPSIS
string() - a MOS task
command string (task name is defined as string):
string"<s>
DESCRIPTION
This routine operates as a MOS pipe task converting the
parameter string s to the corresponding vectors.
SEE ALSO
vector(fax), ts(fax)
TF(FAX) TF(FAX)
NAME
tf - convert a text to the vector format.
SYNOPSIS
tf() - a MOS task
command string (task name is defined as tf):
tf"<width>,<line_sp>,<upper>,<left>
DESCRIPTION
This routine operates as a MOS pipe task converting the in-
put text to the corresponding vectors. The input text, taken
from the Clean and Simple interface should be in the format
defined in text(fax).
+-------------------------+
| |
| upper |
| |
| XXXXXXXXXXXX |
| XXXXXXXXXXXX |
| XXXXXXXXXXXX |
| XXXXXXXXXXXX |
| left XXXXXXXXXXXX |
| XXXXXXXXXXXX |
| XXXXXXXXXXXX |
| XXXXXXXXXXXX |
| XXXXXXXXXXXX |
| width |
| |
+-------------------------+
As shown in the diagram, the parameters give the information
for the formating. The parameter width is the maximum width
of the text lines.
Every vector will be padded to fit this width. White pels
may be padded to the left of each vectors, and the number of
pel to be padded is specified by the parameter left.
Empty lines may also be inserted. They are defined by param-
eters upper and line_sp, the number of pels being used as
the unit.
SEE ALSO
vector(fax), text(fax), ts(fax), fitter(fax)
Appendix III: Utility Routines and Data Formats
BITMAP(FAX) BITMAP(FAX)
NAME
bitmap - convert vector format to core bit map
SYNOPSIS
int bitmap(ivec, cnt, buff);
int *ivec;
int cnt;
char *buff;
DESCRIPTION
Bitmap converts the fax vector format into a bit map, using
each bit of the area pointed to by buff. The number of ele-
ments in ivec is given by cnt, and the first element of ivec
is taken as a white pel count, the second as a black pel
count, etc. The resultant bit map is placed in the area
pointed to by buff. The actual number of bits stored is re-
turned from the function. The bits in buff are stored in
byte order, with the highest value bit of the byte taken as
the first bit of the byte.
BUGS
You have to make sure that buff is big enough for all the
bits.
SEE ALSO
vector(fax), tovec(fax)
TOVEC(FAX) TOVEC(FAX)
NAME
tovec - convert bitmap to vector format
SYNOPSIS
int *tovec(buff, nbits);
char *buff;
int nbits;
DESCRIPTION
The bitmap in the buffer pointed to by buff is converted to
vector format. The length of the bitmap in bits is passed in
nbits. As the caller would normally not know how many vec-
tor elements are going to be needed, the tovec routine allo-
cates this area for the user.
Buff is assumed to be organised in byte order with the
highest value bit of each byte being the first bit of the
byte. The counts of white and black pels are placed into an
integer vector, the first element of which is the length of
the rest of the vector. The vector information proper starts
in the second element which is the count of the number of
leading white pels. This is followed by the count of the
numbr of black pels, etc.
The routine goes to great lengths to make sure only enough
vector storage is allocated. Temporary storage is allocated
in small chunks and then, when the length of the whole vec-
tor is known, the chunks are contacenated into a contiguous
vector. The pointer to this vector is returned to the user.
SEE ALSO
vector(fax), bitmap(fax)
CHOICE(FAX) CHOICE(FAX)
NAME
choice - specify a rectangular area on Grinnell
SYNOPSIS
struct square {
int x0, y0;
int x1, y1;
};
struct square *choice(colour, height, width, area, fw, fh)
char colour;
int height, width, area, fw, fh;
DESCRIPTION
This subroutine is called by a MOS task. to specify a rec-
tangular area of an image by manipulating a square on the
Grinnel display being illustrating the image. The dimension
of the original image is defined as height and width. The
area on which the original image is shown is specified by
the parameter area.
value area dimension coordinates
0 the whole screen 512x512 0,511,511,0
1 the left half 256x512 0,511,255,0
2 the right half 256x512 256,511,511,0
The square will be drwan in a colour defined by the parame-
ter colour, which can only be:
value colour
'r' red
'g' green
'b' blue
There are two modes being supported:
(1) Fixed: The square will have a fixed dimension specified
by the parameters fw and fh. The operator can move the
square around as a whole within the predetermined area
by using following commands, each of which is invoked
by typing the corresponding characer on the keyboard of
the system console.
command function
'u' move the square up one step
'd' move the square down one step
'l' move the square one step left
'r' move the square one step right
'f' move fast - set the step to 8 pel
'o' move slowly - set the step to 1 pel
<CR> ok - the area has been chosen, and
return its coordinates
(2) Arbitrary: This mode is set up when the subroutine is
called with the parameters fw and fh set to 0. Any
edge of the square can be selected to be moved on its
own by using the same commands described above. The
following commands are required to select the relevant
edge as well as switching the operation mode.
command function
'e' select the right ('east') edge.
'w' select the left ('west') edge.
'n' select the upper ('north') edge.
's' select the lower ('south') edge.
'a' move the square as a whole
As soon as the user types <CR>, the coordinates of the
current square, which are accommodated in a square struc-
ture, are returned. Note these are concerned with the coor-
dinate system defined for the image but not for the grin-
nell.
BUGS
Currently, only three working areas can be used.
SEE ALSO
vector(fax), grinnell(dev), grinnell(fax)
CRC(FAX) CRC(FAX)
NAME
crc - calculate or check the DACOM CRC code
SYNOPSIS
int crc(buff, insert);
char *buff;
int insert;
DESCRIPTION
This routine will check/insert the 12-bit CRC code for a
DACOM block, pointed to by buff. The block contains 585
bits, the last 12 bits being the CRC code. The block is
checked only when the parameter insert is set to 0, other-
wise the CRC code is created and inserted into the block.
When the block is checked, the routine returns the result: 0
means OK and any non-zero value means the block is bad. On
the other hand, when the CRC code is inserted, the routine
returns the CRC code it has created.
This routine uses a tabular approach to determine the CRC
code, processing a whole byte at a time and resulting in a
high throughput.
BUGS
Do not forget to supply enough space when the 12-bit CRC
code is to be inserted.
SEE ALSO
dacom(dev)
CSINIT(FAX) CSINIT(FAX)
NAME
csinit - initiate the Clean and Simple interface
SYNOPSIS
int csinit();
DESCRIPTION
This routine is called to initiate the Clean and Simple in-
terface for the calling process. Its code is re-entrant, so
that only one copy is needed for all processes in a system.
This routine returns the task identifier, which must be used
on all subsequent interface calls.
SEE ALSO
csopen(fax), csread(fax), cswrite(fax), fitter(fax)
CSOPEN(FAX) CSOPEN(FAX)
NAME
csopen - establish the Clean and Simple connection
SYNOPSIS
char *csopen(tid);
int tid;
DESCRIPTION
A process calls this routine, waiting to be scheduled. Its
code is re-entrant, so that only one copy is needed for all
processes in a system.
The task identifier tid is the word returned from the csinit
call. When the fitter process has established the Clean and
Simple connection for the process, this routine returns the
pointer to the parameter string of the corresponding task
command.
SEE ALSO
csinit(fax), csread(fax), cswrite(fax), fitter(fax)
CSREAD(FAX) CSREAD(FAX)
NAME
csread - read data from the Clean and Simple interface
SYNOPSIS
char *csread(tid, need);
int tid, need;
DESCRIPTION
This routine is called to read data from the Clean and Sim-
ple interface. Its code is re-entrant, so that only one copy
is needed for all processes in a system.
The task identifier tid is the word returned from the csinit
call. The need parameter indicates the number of bytes that
are required. This routine returns a pointer to a buffer
with this much data in it. This is usually more efficient as
it means that the data does not have to be reblocked.
DIAGNOSTICS
If the returned value is 0, the end of data is reached.
BUGS
Funnies happen at the end of data to be read. The csread()
call has no way of saying that the final buffer is partly
filled. Thus if you ask for more data, you hang forever.
But if the data structures are working correctly, this
should never happen.
SEE ALSO
csinit(fax), cswrite(fax), fitter(fax)
CSWRITE(FAX) CSWRITE(FAX)
NAME
cswrite - write data to the Clean and Simple interface
SYNOPSIS
char *cswrite(tid, need);
int tid, need;
DESCRIPTION
This routine is call to write data to the Clean and Simple
interface. Its code is re-entrant, so that only one copy is
needed for all processes in a system.
The task identifier tid is the word returned from the csinit
call. The need parameter indicates the number of bytes that
are to be written. This routine returns a write buffer of
the required length, to which the user data can be copied.
The subsequent cswrite() call automatically releases the
previous write buffer.
The cswrite() call with need set to 0 indicates the end of
data, closing the current Clean and Simple connection.
BUGS
As indicated, the write buffer must be filled up before the
next cswrite() call.
SEE ALSO
csinit(fax), csread(fax), fitter(fax)
GETL(FAX) GETL(FAX)
NAME
getl - get a line vector from the Clean and Simple interface
SYNOPSIS
int *getl(tid);
int tid, need;
DESCRIPTION
This routine is called to read a line vector from the Clean
and Simple interface. Its code is re-entrant, so that only
one copy is needed for all processes in a system.
The task identifier tid is the word returned from the csinit
call. The routine returns the pointer to the buffer where
the line vector is stored.
DIAGNOSTICS
0 will be returned when end of file is reached.
BUGS
Any memory violation causes the whole task chain to be
aborted.
SEE ALSO
vector(fax), putl(fax), fitter(fax)
PUTL(FAX) PUTL(FAX)
NAME
putl - put a line vector to the Clean and Simple Interface
SYNOPSIS
putl(tid, buf);
int tid, *buf;
DESCRIPTION
This routine is called to write a line vector to the Clean
and Simple interface. Its code is re-entrant, so that only
one copy is needed for all processes in a system.
The task identifier tid is the word returned from the csinit
call. The line vector is stored in a buffer pointed by buf.
SEE ALSO
vector(fax), getl(fax), fitter(fax)
T4(FAX) T4(FAX)
NAME
t4 - the data format defined in CCITT recommendation T4
DESCRIPTION
Dimension and Resolution: In vertical direction the resolu-
tion is defined below.
Standard resolution: 3.85 line/mm
Optional higher resolution: 7.70 line/mm
In horizontal direction, the standard resolution is defined
as 1728 black and white picture elements along the standard
line length of 215 mm. Optionally, there can be 2048 or
2432 picture elements along a scan line length of 255 or 303
mm, respectively. The input documents up to a minimum of ISO
A4 size should be accepted.
One-Dimensional Coding: The one-dimensional run length data
compression is accomplished by the popular modified Huffman
coding scheme. In this scheme, black and white runs are re-
placed by a base 64 codes representation. Compression is
achieved since the code word lengths are invertly related to
the probability of the occurrence of a particular run. A
special code (000000000001), known as EOL (End of Line),
follows each line of data. This code starts the facsimile
message phase, while the control phase is restored by a com-
bination of six contiguous EOLs (RTC). The data format of a
facsimile message is shown below.
start of the facsimile data
|
v
+---+------+---+------+-/
!EOL! DATA !EOL! DATA !
+---+------+---+------+-/
end of the facsimile data
|
v
/-+---+------+---+---+---+---+---+---+
!EOL! DATA !EOL!EOL!EOL!EOL!EOL!EOL!
/-+---+------+---+---+---+---+---+---+
|<------ RTC ------->|
Two-Dimensional Coding: The two-dimensional coding scheme is
labeled as the Modified READ Code. It codes one line with
reference to the line above,correlation between adja-
cent lines allowing for more efficient compression. In order
to limit the disturbed area in the event of transmission er-
rors,
a one-dimensionally coded line is transmitted after one or
more two-dimensionally coded lines. A bit, following the
EOL, indicates whether one- or two-dimensional coding is
used for the next line:
EOL1: one-dimensional coding;
EOL0: two-dimensional coding.
start of the facsimile data
|
v
+----+--------+----+--------+-/
!EOL1!DATA(1D)!EOL0!DATA(2D)!
+----+--------+----+--------+-/
end of the facsimile data
|
v
/-+----+--------+----+----+----+----+----+----+
!EOL0!DATA(2D)!EOL1!EOL1!EOL1!EOL1!EOL1!EOL1!
/-+----+--------+----+----+----+----+----+----+
|<--------- RTC --------->|
TEXT(FAX) TEXT(FAX)
NAME
text - the text format for use in the facsimile system
DESCRIPTION
This is the representation structure for coded character
text. It is used in the facsimile system.
The text structure consists of a series of character
strings, each of which represents a text line. However no
control characters, e.g. <CR> and <LF>, are used in the
structure. Each text line is proeeded by a count byte, indi-
cating the number of characters on the line. The character
sting follows after the the count byte. A zero count indi-
cates the end of file.
EXAMPLES
Here is an example text shown below:
This is a text.
This is a picture.
It can be represented as:
<017> T h i s <040> i s <040> a <040> t e x t .
<022> T h i s <040> i s <040> a <040> p i c t u
r e . <0>
TS(FAX) TS(FAX)
NAME
ts - translate an ASCII string into vector format
SYNOPSIS
ts(ar_in, left, right, tid)
char *ar_in;
int left, right, tid;
DESCRIPTION
This routine will convert a zero-ended ASCII string pointed
to by ar_in into the corresponding vecter format. As the
character font being used is a set of 12x20 matrices, there
will be 20 line vectors created. These vectors are written
to the Cleans and Simple interface by calling cswrite. The
callers task identifier tid has to be provided.
At the two ends of the text line, blanks can be padded that
are specified as left and right. Note that they are meas-
ured in pels.
Consequently, the result should be a image, whose dimension
is:
width = left + 12*length + right;
height = 20;
where length is the number of characters in the input
string.
As an intermediate result the bitmap is first created which
is then converted into the vector format, by calling tovec.
BUGS
The input string must be ended with a zero field.
SEE ALSO
vector(fax), tovec(fax), csinit(fax), cswrite(fax),
fitter(fax)
VECTOR(FAX) VECTOR(FAX)
NAME
vector - the internal data structure for a facsimile image
DESCRIPTION
This is the representation structure for binary images, a
simple run length compression algorithm being used. Most of
the image files are kept in vector format for ease of pro-
cessing.
The vector format consists of a series of integer vectors,
one vector for each row of pels in the image. Each vector is
proceeded by a count word which indicates the number of in-
teger words in the vector. The next element of the vector
after the count field is the number of white pels in the
first run of the line. The second word then gives the
number of pels that follow the initial white run, and so on
t the end of the vector. Note the first run length element
must refer to a white run. It should be set to 0 if the
first run is black.
EXAMPLES
A line consists of 20 pels as follows:
00011111111011100000
It can be represented as:
5, 3, 8, 1, 3, 5
The inverse of the line:
11100000000100011111
should be represented as:
6, 0, 3, 8, 1, 3, 5