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 00002 00002	USER PROGRAM DOCUMENTATION			       SEPTEMBER 1973
 00004 00003	INTRODUCTION.
 00006 00004	TVFONT PRIMER.
 00011 00005	Polygon Killing.
 00014 00006	TVFONT COMMAND SUMMARY
 00016 00007	TVFONT COMMAND SUMMARY
 00018 00008	TVFONT COMMAND SUMMARY
 00020 00009	TVFONT'S EXTENDED COMMANDS.
 00022 00010	TVFONT'S EXTENDED COMMANDS.
 00025 00011	TVFONT NODE FORMATS - JAN 1973.
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USER PROGRAM DOCUMENTATION			       SEPTEMBER 1973
draft - draft - draft - draft - draft - draft - draft - draft - draft

                  TVFONT  -  Television Font Maker.

                          Bruce g. Baumgart
				Tovar


ABSTRACT:

	TVFONT  is  a  program for  creating  XGP  fonts  from  video
images; and for editing and scaling an existing font.

CONTENTS:

	1.0	INTRODUCTION.
	2.0	PRIMER.
	3.0	COMMAND LETTERS.
	4.0	EXTENDED COMMANDS.
	5.0	FILE FORMATS.


	This research was supported in part  by the Advanced Research
Projects  Agency of  the  Office of  the Secretary  of  Defense under
Contract No. SD-183.

	The views  and  conclusions contained  in this  document  are
those  of the  author and  should not  be interpreted  as necessarily
representing  the official policies, either  expressed or implied, of
the  Advanced   Research  Project   Agency  or   the  United   States
Government.
INTRODUCTION.

	TVFONT  is  a   version  of  CRE  (January  1973)   that  was
specialized  to the  task of converting  television images  into type
fonts for the XGP,  Xerox Graphics Printer. The original idea  was to
demonstrate  the utility  of  a polygon  representation for  scaling,
smoothing  and  editing  typographical  glyphs;  the  resulting  hack
(demonstration program)  was  extended and  developed  by Tovar  Mock
into the program called  TVFONT. Accordingly, the main idea of TVFONT
is to convert  video rasters  into polygons,  to edit  and scale  the
polygons, and to convert the polygons back into bit rasters.
TVFONT PRIMER.

	TVFONT is on the system, and can be  run by typing "R TVFONT"
at  a III display console.  At present, III  #23 is next  to a camera
setup for making  fonts.   The process of  making a new  XGP font  or
altering an old one will be explained in six steps:

	1.  Raster input:	get a video image or an old font.
	2.  Contouring:	 	make polygons.
	3.  Polygon editing:	delete, scale, position and alter.
	4.  Polygon I/O:	save and restore polygons.
	5.  Font output:	make new font and output font file.

	Complexity arises in  that there is  more than one way  to do
each  step, there are  default arguments  and switchs which  the user
may alter, there are ways  to save and restore intermediate  results,
and  there  are  quite a few  different  display  modes  and  display
diagonostics.  The TVFONT command scanner resembles  that of TVED and
E;  (as well  as  CRE  and  GEOMED); the  command  scanner  types  an
asterisk "*"  when it is  in its top  most listen loop  waiting for a
single command character.  The command character  may be modified  by
the META and CONTROL  keys which will be abbreviated as  "α", "β" and
"ε"  for CONTROL, META, and  META-CONTROL respectively. Many commands
in turn require arguments such as numbers or file names.  Finally the
"X"  command   waits  for  an   extended  command  name   of  several
characters, which is called an extended command.

	This first  explanation will present  a way  of making a  new
font  using the fewest  commands.

Raster Input and Contouring:
	1.	"T"	take television picture.
	2.	"H"	Display histogram of television picture.
	3.	"C24"	Cut at intensity level 24.

	Get the  Font Camera  looking at  a single  letter in a  font
book. Use  a black piece of paper with a square  cut out as a mask to
isolate the letter. The "T"  command will take a television  picture.
The "H" command  will display a histogram of  the television picture,
showing how  many points of the image were 0 intensity, (total black)
and how many points of the image were 77  intensity, (total white). A
picture of a black glyph  on a white background surrounded by a black
mask should yield a  histogram with two peaks.

	Next the "C" command followed by an  octal number followed by
a  carriage return; contours the  image at the  given octal intensity
cut threshold.    That is  all  the points  of  the image  above  the
threshold  are inside  of  a polygon.   The  intensity  value of  the
lowest valley  between the two peaks of the histogram is probably the
best cut value (and is  probably the octal number 24 or 30).  The cut
command, will display the polygons that are made.
Polygon Killing.

	4.	"ε+"	Fetch 1st polygon of 1st image of the film.
	5.	"K"	Kill a polygon.
	6.	"."	ring around the polygons of an image.
	7.	"!"	flush node display.

	Given  an image  of  polygons  corresponding to  one  letter,
undesired  polygons can be deleted  by using the "K"  command and the
node link display  commands. To  start, the "ε+"  will intensify  the
first  polygon  of the  image's  polygon  ring;  from there  the  "."
commands  will  intensify  the  next polygon  of  the  ring;  the "K"
command will delete the  presently intensified polygon and  fetch the
next polygon.

	A font  corresponds  to a  film. An  image  corresponds to  a
letter.  After  taking a  series  of iaages,  and  deleting undesired
polygons a font file can be made using:

Making and Outputing a Font File.

	8.	"X"CENTER	Center all the images of the film.
	9.	"Q"		Make font bit rasters.
	10.	"εO"		Output font file.


	The "X"CENTER command is an extend  mode command and requires
both  hitting "X"  and typing  out  the word  "CENTER" followed  by a
carriage return. The "Q" will cause  a bit raster to be made for  the
interior portions  of each image of  the film; if an  image node does
not  have an associate ASCII code then  the user will be requested to
supply one. The "εO" will  ask for a font filename and will  output a
font file in the Stanford Format.

Testing a new Font File.

	11.	.XGP FILE/FONT=NEWFNT.FNT[XGP,BGB]

	The above monitor command will print a FILE with a new font.
The user must specify his PPPN because the default is [XGP,SYS].
TVFONT COMMAND SUMMARY

 A	ASSIGN ASCII CODE TO IMAGE.
 B	EXPAND/CONTRACT BY CONSTANT
αB	EXPAND/CONTRACT IN Y DIRECTION
βB	EXPAND/CONTRACT IN X DIRECTION
εB	SLANT CHARACTER (1/2 SLANTS TO 45 DEGREE ANGLE)

 C	MAKE THRESHOLD CUT.
εC	MAKE POLYGON IMAGE OUT OF BIT REPRESENTATION OF FONT.
 D	ENABLE/DISABLE DELETION OF BABY POLYGONS (DEFAULT IS OFF).
 F	LOCATE NEAREST POINT, εF USE LIGHT PEN
 G	LEVEL OF CORRESPONDING CHARACTER CODE

 H	HISTOGRAM, "αH" ,"βH" BI-MODAL CUT.
 I	INPUT TV PICTURE FROM DISK.
αI	INPUT CRE FILE
βI	INPUT CRUNCHED FILE
εI	INPUT FONT FILE INTO FONT SEGMENT (SEE `READFONT')
 K	KILL IMAGE, POLYGON OR VERTEX
 L	SHOW LAST BIT IMAGE

αL	SHOW CHARACTER FROM FONT IN FNTSEG
 M	MOVE POLYGON TO NEXT IMAGE.
αM	MOVE TO NEW IMAGE
βM	MIDPOINT LINE
εM	MUNG ONTO GRID POINT (AS SEEN IN εY)

 N	NEXT IMAGE
αN	PREVIOUS IMAGE
βN	REPEAT NEXT IMAGE UNTIL A CHARACTER IS TYPED
εN	REPEAT PREVIOUS IMAGE UNTIL A CHARACTER IS TYPED
TVFONT COMMAND SUMMARY

 O	OUTPUT CAREYE FILE.
αO	OUTPUT CRE FILE
εO	OUTPUT FONT FILE
 P	PLOT OUTPUT FILE.

 Q	MAKE FONT
αQ	MAKE 1/2 SIZE FONT
 R	DISPLAY BIT MATRIX FOR THIS CHARACTER.
αR	ROTATE IMAGE, LEVEL OR POLYGON (ANGLE IN RADIANS)

 S	SMOOTH
αS	SMOOTH AND KILL VIDEO INTENSITY CONTOUR
βS	REPEAT 'S' FOR EACH IMAGE
εS	REPEAT 'αS' FOR EACH IMAGE
 T	TAKE A TV PICTURE
αT	TAKE A TV PICTURE, SETTING CLIP LEVELS AUTOMATICALLY

 V	CREATE VERTEX AT CENTER
αV	CREATE NEW VERTEX AT CURRENT VERTEX
βV	CREATE NEW VERTEX IN NEW IMAGE

 W	CENTER IN THE WINDOW.
αW	CENTER Y-POSITION ONLY.
βW	CENTER X-POSITION ONLY.
εW	MOVE POINT SPECIFIED BY LIGHT PEN TO CENTER.

 X	XTEND MODE COMMANDS

 Y	DISPLAY SMOOTHED FORM
βY	DISPLAY VIDEO INTENSITY CONTOUR
αY	DISPLAY BOTH OF ABOVE
εY	DISPLAY VIDEO INTENSITY CONTOUR MUNGED ONTO PIXELS

 Z	NO-OP
αZ	RESET LOGICAL CAMERA POSITION
βZ	RESET DISPLAY
TVFONT COMMAND SUMMARY

	 +	Fetch film node.
	α+	Fetch first image node from film.
	β+	Fetch first level from film.
	ε+	Fetch first polygon from film.

IF A NODE IS CURRENTLY BEING DISPLAYED, THESE COMMANDS AFFECT THAT NODE,
OTHERWISE THEY AFFECT THE CAMERA (VIEWERS) POSITION. <CONTROL> MULTIPLIES
BY 2, <META> MULTIPLIES BY 4.  
;	MOVE LEFT (←) BY DELTA
:	MOVE RIGHT (→) BY DELTA
(	MOVE UP BY DELTA
)	MOVE DOWN BY DELTA
/	DIVIDE DELTA BY 2
\	MULTIPLY DELTA BY 2

THESE COMMANDS AFFECT THE CAMERA (VIEWERS) POSITION.
*	INCREASE MAGNIFICATION BY DELTA
-	DECREASE MAGNIFICATION BY DELTA

THESE COMMANDS CHANGE NODE BEING DISPLAYED.
.	FETCH COUNTER CLOCKWISE NODE IN RING.
,	FETCH CLOCKWISE NODE IN RING.
<	FETCH FATHER OF NODE
>	FETCH SON OF NODE
≤	FETCH ARC [OF POLYGON OR VERTEX]
→	FETCH POLYGON [OF VERTEX]
∧	EQUIVALENT TO '<,>'
∨	EQUIVALENT TO '<.>'
!	FLUSH NODE DISPLAY

THESE COMMANDS AFFECT THE PUSHDOWN LIST
∪	PUSH NODE BEING DISPLAYED ONTO STACK
∩	POP NODE OFF STACK AND DISPLAY IT
↔	SWAP NODE BEING DISPLAYED WITH TOP OF STACK
TVFONT'S EXTENDED COMMANDS.


ARCWID
	Set smoothing constant.  This is the maximum distance a vertex 
	may from a arc before it is split into two arcs.  See description
	of smoothing algorithm on page XX.

BABYKILL
	Toggle flag which causes baby polygons (those consisting of only
	one pixel) to be killed)

CAMERA
	Select a different camera number.

CENTER
	Center all images.  It is equivalent to the command 'W' applied
	to each image and uses the same control bits.

DDT
	Invoke DDT if present, return with αP..

DISPLAY
	Enable display.

-DISPLAY
	Disable display.  TVFONT spends a significant amount of time
	putting up the display.

EXIT
	Exit to moniter.

GRID
	Enable display of grid.  Grid is some multiple of pixel size,
	dependent on camera focal length.  It is useful of lining up
	characters.

-GRID
	Disable display of grid.

HELP
	Display help file.

HOLE
	Change a polygon into a hole.

KILARC
	Kill arcs vectors.  This allows several degrees of smoothing to
	be tried in conjunction with the ARCWID command.
TVFONT'S EXTENDED COMMANDS.


KILVIC
	Kill video intensity contours and replaces them with arcs.

MUNG
	Force all vertices of current polygon or level onto pixel boundaries.
	This has a permanent effect as opposed to 'εY' command which only
	displays them that way.

ORTHMUNG
	ORTHMUNG forces vertices which appear to be form right angles onto
	pixel boundaries.  This is attempt to counter the rounding effect
	of dekinking on sharp corners as are generated by reading a font.

POLYGON
	Change a hole into a polygon

POPJ
	Leave TTY loop.  Used for debugging.

READFONT
	Convert font which has been read into the font segment into polygonal 
	representation, displaying each character as read.

SCALE
	Scale all images by constant.  Equivalent to the command 'B' applied
	to each image.

SLANT
	Slant all images by constant .  Please see command 'εB' for a more
	complete description.

SORT
	Sort images on film according to ASCII code.  This is for convienence
	in looking a fonts sequentially.  The 'G' command is recommended for
	finding specific characters.

XEROX
	OUTPUT TV IMAGE TO XGP

XSCALE
	Scale all images by constant in the X direction.  Equivalent to the
	command 'αB' applied to each image.

YSCALE
	Scale all images by constant in the Y direction.  Equivalent to the
	command 'βB' applied to each image.
TVFONT NODE FORMATS - JAN 1973.

 ________________________________________________________________
|								 |
|       VERTEX/ARC NODE.	POLYGON/REGION NODE.		 |
|								 |
|	0   VERTEX-RING		0   POLYGON-RING.		 |
| 	1   ROW,,COL		1   DAD,,SON  			 |
|	2   TYPE,,RELOC		2   TYPE,,RELOC			 |
|	3    - ,, -		3    - ,, -			 |
|	4   ARC,, -		4   ARC,,NCNT          		 |
|	5    - ,,PGON		5    - ,,PGON			 |
|	6   RT SEG,,LT SEG	6    - ,, -			 |
|________________________________________________________________|
|								 |
|       IMAGE NODE.             LEVEL NODE.			 |
|								 |
|	0   IMAGE-RING		0   LEVEL-RING			 |
| 	1    - ,,SON  		1    - ,,SON 			 |
|	2   TYPE,,RELOC		2   TYPE,,RELOC			 |
|	3    - ,, -		3    - ,, -    			 |
|	4    - ,, -		4    - ,,NCNT 			 |
|	5    - ,, - 		5    - ,, -			 |
|	6    - ,, -		6    - ,, -     		 |
|________________________________________________________________|
|								 |
|       FILM NODE.              EMPTY NODE.			 |
|								 |
|	0   CORESIZE 		0    - ,,AVAIL			 |
| 	1    - ,,SON  		1    - ,, -			 |
|	2   TYPE,,RELOC		2   TYPE,,RELOC			 |
|	3    - ,,AVAIL  	3    - ,, -    			 |
|	4   BLOCK COUNT		4    - ,, - 			 |
|	5    - ,, - 		5    - ,, -			 |
|	6    - ,, -		6    - ,, -     		 |
|________________________________________________________________|
|								 |
|	SEGMENT NODE.						 |
|	0   SEGMENT RING					 |
|	1    - ,, -						 |
|	2   TYPE,,300003					 |
|	3   LDEL,,RDEL						 |
|	4   LCOL,,RCOL						 |
|	5   LROW,,RROW  					 |
|	6   LT,,RT						 |
|________________________________________________________________|