The "digitz" program in GGLIB is a quick-and-dirty way of entering a line
drawing into the system for use as a GIGI picture file.

To run it, the command is:

	$ run gglib:digitz

Two output files are produced.  One is named "digitz.pic", and is a ReGIS
picture file suitable for use by the Slide Projector or Graphics Editor.
(It generates a few error messages when it's read by GE, but it gives
the right result, anyway.)  The other file is called "digitz.log", and is
just a debugging file listing all the tablet inputs.

After one picture is created, the "digitz.pic" file should be renamed to
a permanent file name, since the next time you run "digitz", another version
of that file will be created.  You can delete the "digitz.log" file.


The "digitz" program has no prompts (other than the crosshairs cursor) and
allows no recovery from mistakes (that's what GE is for).  All the commands
except "e" and "q" (for "end" and "quit" -- either exits the program) are
given by pressing buttons on the Bit Pad's four-button cursor.  The program
immediately executes each button press and then sounds a bell to indicate
it's ready for the next button press.

There are only four drawing commands, since there are only four buttons.
They correspond very closely to ReGIS commands.

The yellow button, is the "position" command -- it establishes the
"current position" used in executing whatever command follows.  It also
terminates any curve interpolation sequence, if one is in progress.
The position set by the position command is the location of the crosshairs
at the time the button was pressed.

The white button is the "line to" command -- it draws a line from the
previous "current position" (set by the previous white or yellow button)
to the point at which the crosshairs now cross.  It also changes the "current
position" to be the point to which the line was drawn -- thus a series
of connected lines can be drawn by pressing the yellow button once, at the
starting point, and then repeatedly pressing just the white button
at each vertex.  The white button also terminates any curve interpolation
sequence, if any is in effect at the time.

The blue button is the "circle circumference" command.  It is used to draw
circles.  To draw a circle, first set the center of the circle with
the yellow "position" button, and then place the crosshairs at any point on
the circumference of the circle.  Pressing the blue button draws a circle
through the crosshairs location with center at the previous "current location".
The "current location" is not changed by the blue button;  thus repeatedly
pressing the blue button draws concentric circles.  The blue button will
terminate any curve sequence in progress.

The green button is the "curve interpolation" command.  It is used to draw
open curves of indefinite length.  Note that, as in ReGIS itself, the
first point of the curve is not drawn unless it is specified both as the
"current position" AND as the first point of the sequence.  Assuming that
you do want to draw from your starting position, rather than the second point,
first press the yellow "current position" button and then press the green
"curve" button at the same point.

Note that another characteristic of ReGIS is that the drawing of the curve
on the screen will lag behind the points as entered by one point.
Also, the last point in the sequence will not be drawn to unless it is
specified twice -- which is easily done by hitting the green button twice
at the end point.  Note that using any of the other buttons will terminate
the curve sequence, drawn only up to the next to last point.

The "digitz" program will draw the image on the screen as you enter it from
the Bit Pad.  The aspect ratio of the screen image will be off, with the
image appearing twice as wide on the screen than it really is.  This is
done so that the crosshairs position as displayed on the screen matches
up with the points drawn on the screen.  The data written to the ReGIS file,
"digitz.pic", is scaled so that the image has its normal appearance.

This program is quick-and-dirty, and experimental.  It sometimes "hangs up"
due to an obscure firmware bug that may be alleviated by reducing the speed
used by the Bit Pad (requires changing switches within the Bit Pad, and
the "HS" SET-UP parameter).

If it hangs, you should press SET-UP, type "RS" followed by the digit "d",
where "d" is the speed already displayed after "RS" (i.e, if it displays
"RS3" after you type "RS", then the digit to type is "3"). Then leave SET-UP
and type a carriage return.  DIGITZ should resume at that point.
If this doesn't work, reset the terminal and type control-C to abort DIGITZ.
Rename and examine the "digitz.pic" file to see how much was saved.
You can restart the "digitz" program, create the rest of the image, and then
append the previous output to the remaining output to get the whole
picture.

("Bit Pad" is a trademark of Summagraphics.)
