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Data flow (flowchart)
28.
FIFO
29.
GA2
(Zooming)
28. FIFO
Image data of one line are stored in the line memory (FIFO). This FIFO is for zooming.
For reduction, the scanned image data are thinned out when they are written into the
FIFO. For enlargement, the scanned image values are used as the values of plural
pixels of the next one.
29. Gate array 2
Gate array 2 outputs the control signal to the FIFO to perform reduction and enlarge-
ment. Interpolation is also performed, which eliminates notches generated in enlarge-
ment. Two neighboring pixels before enlargement are interpolated primarily to eliminate
notches.
A
: Density of pixel in normal ratio ( 0 ∼ 255)
D5 D6
d1:
Position if a pixel to be inserted.
Density of the pixel which was formed by interpolation. (0 ∼ 255)
C:
C: (1 – d1) ×
ICU PWB
Example 1: Calculation of interpolation
Supposing that the density of
200, and that the position of new pixel C after zooming is at 50% position, the density of
C is as shown below.
A
100
0
= (1 – 0.5) × 100 + 0.5 × 200
D7
↓
d1
= 150
↓
Density of new pixel C
Example 2: In the case of enlargement
In the case of enlargement of 200%, the image process is made so that the number of
pixels will be twice as greater as the number of the scanned pixels.
In short, the number of pixels scanned in the normal mode is duplicated to enlarge to
200%. One pixel in the normal mode is duplicated to two pixels in 200%. (Refer to the
description below.)
A
B
C
Then the density of pixels newly formed in the image process is determined. As shown
in example 1, the position of newly made pixel is at the center (50% position) of two
pixels scanned in the normal mode and the primary interpolation is performed as fol-
lows:
A
B
=
In the image process, enlargement is performed only in the main scanning direction. In
the sub scanning direction, the scanning sped of the optical system is changed to
perform enlargement. (For example in 200% enlargement, the scanning speed is
changed to 1/2, and 50% enlargement is performed by duplicating the scanning speed.)
The main scanning is performed by image process, and the sub scanning by varying the
speed of the optical system. Zooming in the main scanning direction is separately
performed from zooming in the sub scanning direction.
Content
C
d1
⇓
+ d1 ×
D6
D5
at the normal ratio is 100 and that the density of
D5
C
0.5
d1
(50%)
↓
↓
↓
A
d1
B
D
G
E
F
H
I
A
D
+
C
E
D
F
=
=
2
1 – 6
B
B
200
(Normal)
(200%)
D
G
+
=
2
is
D6
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