perm filename PAGE43[00,BGB] blob
sn#047835 filedate 1973-06-07 generic text, type T, neo UTF8
~F8TVFONT PRIMER - (draft).
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.
~I1973,800;F8- 43 -