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Image Functions
Halftone reading
3.2.4
This scanner supports two types of halftone image, that is Dither and Error Diffusion.
NOTICE: The density of the halftone can not be adjusted by the Threshold in Table 3.4 but the
(1)
Dither
This is a way of producing halftone images with white and black pixels. The scanned image is
processed by the unit of group of pixels.
At first a reference table called "dither matrix" is specified. Each element in the matrix (8x8)
has a threshold value of 256 levels. Allocation of threshold values in the dither matrix is called
"dither pattern". Group of the scanned images are compared with the dither pattern, and each
element is decided whether it is black or white. Number of black pixels corresponds to a level
of scale, producing pseudo grayscale images.
Four built-in dither patterns are available. Parameters which affect dither are shown in Table
3.7.
Halftone reading ON
Dither ON
Density *1
8 step setting ON
256 step setting ON
Contrast
Mostly soft contrast
Normal
Mostly sharp contrast
Dither
Bult-in
pattern No.
Download *2
*1
Effective only for Built-in pattern
*2
IPC-2D or OPC-3D required. (See section 3.3.5)
3-10
Brightness in Table 3.5.
Table 3.7 Parameter of dither
Parameter
set from operator panel
Light
Normal
Dark
Light
to
Dark
0
1
2
3
0
to
7
Control register No.
A#2/B#2
A#19/B#19
A#19
A#1/B#1
A#19
A#20/B#20
A#21/B#21
A#2/B#2
value
Default
B'xxxx11xx'
ON
B'xxxx000x'
B'xxxxxxx0'
Set from
B'xxxx00xx'
operator
B'xxxx1000'
panel
to
B'xxxx1100
to
B'xxxx1111'
B'xxxxxxx1'
X'01'
to
X'FF'
X'01'
to
X'80'
X'80'
to
X'FF'
B'0000xxxx'
B'0001xxxx'
B'0010xxxx'
B'0011xxxx'
B'1000xxxx'
to
B'1111xxxx'
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