Ricoh A230, Service Manual, Page: 76 / 1134

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IMAGE PROCESSING
2-13
A230/A231/A232 SM
Independent dot erase
By default, this process is used only in letter mode and copied original mode.
However, it can be enabled for other modes by SP mode. It erases independent
black dots appearing in the copy or reduces their image density.
The software compares each pixel (C in the diagram above left) with the pixels
around the edges of the surrounding 3 x 5 area. If the sum of the pixels at the
edges is smaller than the threshold value stored in SP4-903-28 ~ 32 (e.g., for letter
mode with binary picture processing, it is SP 4-903-29), the object pixel is changed
to 0 (white) or reduced in density to an average of the pixels around the edge,
depending on the SP mode setting. Each SP mode has 16 levels as follows.
A= The sum of the pixels at the edges
SP mode
value
Function
SP mode
value
Function
0 Disabled 8 Disabled
1 If A < 16, the pixel is deleted 9 If A < 16, density is reduced
2 If A < 32, the pixel is deleted 10 If A < 32, density is reduced
3 If A < 48, the pixel is deleted 11 If A < 48, density is reduced
4 If A < 64, the pixel is deleted 12 If A < 64, density is reduced
5 If A < 80, the pixel is deleted 13 If A < 80, density is reduced
6 If A < 96, the pixel is deleted 14 If A < 96, density is reduced
7 If A < 128, the pixel is deleted 15 If A < 128, density is reduced
Pixel density reduction works as follows. For the example in the above drawing, ,
when the SP mode value is “11”, the sum of the pixels around the edge is less than
48, the object pixel value is reduced from “90” to “3” as shown below.
A: (0 + 0 + 30 + 7 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0) / 12 = 3
A1
A6
A8 A9 A10 A11 A12
A7
A5 A4 A3 A2
C
0
0
0 0 0 0 0
0
0 7 30 0
90
Original image
3 x 5 area
Image data