COMMENT ⊗   VALID 00011 PAGES
C REC  PAGE   DESCRIPTION
C00001 00001
C00002 00002	III. USING TVFONT.
C00004 00003	TVFONT PRIMER.
C00008 00004	TVFONT PRIMER:	FIRST EXPLANATION.
C00011 00005	Polygon Killing.
C00012 00006	Data Structure:
C00014 00007	TVFONT COMMAND SUMMARY
C00016 00008	TVFONT COMMAND SUMMARY
C00018 00009	TVFONT COMMAND SUMMARY
C00020 00010	SUMMARY OF TVFONT'S EXTENDED COMMANDS.
C00022 00011	TVFONT NODE FORMATS.
C00025 ENDMK
C⊗;
III. USING TVFONT.

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.  My 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 several times 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  afew  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.
TVFONT PRIMER:	FIRST EXPLANATION.

	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 first polygon of first image of the film.
	5.	"K"	Kill a polygon.
	6.	"."	ring around the polygons of an image.
	7.	"!"	flush node display.

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.

Testing a new Font File.

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

Data Structure:

	The internal  data structure of  TVFONT is a  modification of
Baumgart's  CRE structure (Contour Region  Edge). The basic structure
is a doubly-linked  ring of fixed  size nodes.   These nodes  contain
links,   numbers,  type   and  relocation   information.  Nodes   are
explicitly  returned to the empty node  list hence garbage collection
is not necessary, but there is a compactor which  reduces the size of
node space by moving empty nodes to the top of core.

Basic node types:

	The  basic  node  types  used  in  TVFONT  are  film,  image,
polygon, vertex, and  arc.   In addition,  the node  type SEGMENT  is
used by the scan convertor on a temperary basis.

	The lowest level  node is the  VERTEX node, which  contains a
row  and  column number,  a  pointer  to its  owner,  and  possibly a
SEGMENT.  An ARC is a  type of VERTEX which results from smoothing  a
VIC  (Video Intensity  Contour,  which  is a  set  of vertices  which
represent  an intensity contour in  the TV picture  from which it was
derived).  At  the current time,  arcs are straight  lines but it  is
hoped that they will eventually represent curves.
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
K	KILL 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

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	ZERO DATA BUFFERS.
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

SUMMARY OF TVFONT'S EXTENDED COMMANDS.

XEROX	OUTPUT TV IMAGE TO XGP
HELP	DESCRIBE XTENDED FUNTIONS
DDT	INVOKE DDT IF PRESENT, RETURN WITH αP
EXIT	EXIT TO MONITER
ARCWID	SET CONSTANT FOR SMOOTHING

DISPLA	TURN ON DISPLAY
-DISPL	TURN OFF DISPLAY
KILVIC	FLUSH PRE-SMOOTHING LINES
GRID	TURN ON GRID
-GRID	TURN OFF GRID

CAMERA	SELECT CAMERA, "αS" BCLIP, "βS" TCLIP.
KILARC	KILL ARC VECTORS
CENTER	CENTER ALL IMAGES
POPJ	LEAVE TTY LOOP
BABYKI	TOGGLE FLAG WHICH BABY POLYGONS

SCALE	SCALE ALL IMAGES BY CONSTANT
xSCALE	SCALE IN X ALL IMAGES BY CONSTANT
YSCALE	SCALE IN Y ALL IMAGES BY CONSTANT
SLANT	SLANT ALL IMAGES BY CONSTANT
MUNG	FORCE VECTICES OF CURRENT POLYGON OR LEVEL ONTO PIXEL BOUNDARIES

POLYGO  MAKE HOLE INTO POLYGON
HOLE	MAKE POLYGON INTO HOLE
SORT	SORT IMAGES ON FILM ACCORDING TO ASCII CODE
READFO	READ FONT FILE INTO POLYGON REPRESENTATION
TVFONT NODE FORMATS.

 ________________________________________________________________
|								 |
|       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						 |
|________________________________________________________________|