Canon GP215 Service Manual page 101

5. Negative/Positive Reversal
The negative/positive reversal circuit executes
the following image processing:
• Negative/positive reversal
• Framing
• Blanking
• Pasting
a. Negative/Positive Reversal
Level conversion is executed so that the white
area of an original will be black and the black area
will be white on copies.
Output level
255
200
128
55
0
0 55 128
Input level
Figure 3-332 (concept of level conversion)
(original)
a b c
Figure 3-333
COPYRIGHT © 1996 CANON INC.
200 255
(copy)
a b c
CANON GP215/200 REV.0 JULY 1996 PRINTED IN JAPAN (IMPRIME AU JAPON)
3. OPERATIONS AND TIMING
b. Framing/Blanking
For framing/blanking, areas may be as many
as 4 areas; for a rectangle, as many as 10 points
may be specified.
Framing
The signals representing non-specified areas
are forced to represent white.
Area
Figure 3-334 Framing
Blanking
As opposed to framing, the signals represent-
ing the specified area are forced to represent
white.
Figure 3-335 Blanking
e. Pasting
This function may be used when the Retention
Memory Unit (option) is installed. Images stored
in the retention memory in advance and the
image on the copyboard glass are synthesized for
output.
Area
3–47