IMAGE PROCESSING 26 January, 2001
6-28
Independent dot erase
By default, this process is used only in text mode and generation mode to erase
independent black dots appearing in the copy or reduce their image density.
However, it can be enabled for other modes with the following SP modes.
60 Independent Dot Erase Level (Text)
62
Independent Dot Erase Level (Text/Photo)
63
Independent Dot Erase Level (Pale)
SP4903
64
Independent Dot Erase Level (Generation)
The machine compares each pixel (see the diagram below) 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 the SP, 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= 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
following 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
0 0
0
0
0
0 0 0
0
090
30
7
B004D503.WMF
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