IBM CF Series manual J Binary Filter Parameters

5.1.19(J) BINARY FILTER PARAMETERS

The binary filter is used to improve image quality by either removing noise pixels

( speckle removal ) or filling small gaps. Removing means that a pixel which had been classified as foreground ( mark ) is changed to background ( media ). Filling means that a pixel which had been classified as background ( media ) is changed to foreground

( mark ). The decision to remove or fill in a pixel is made based the classifications of pixels in its neighborhood. For example, a foreground pixel completely surrounded by background pixels is a good candidate for removal.

The scanner electronics maintains three separate neighborhood rings around the pixel under consideration: 3 x 3 , 5 x 5 , and 7 x 7. These may be used separately or in combination. Different neighborhoods may be used for fill and removal. Neighborhood selection is coded as follows:

Neighborhood
Parameter	Selected Area
______________	__________________________
1	3 x 3
2	5 x 5
3	3 x 3 and 5 x 5
4	7 x 7
5	3 x 3 and 7 x 7
6	5 x 5 and 7 x 7
7	3 x 3 and 5 x 5 and 7 x 7

The scanner computes a sum of the pixels in the selected neighborhoods ( foreground pixels are given value 1 and background pixels are given value 0 ) and compares it against a threshold parameter. This comparison determines whether a pixel is removed or filled in. The strength of the filter is determined by the threshold value. When removing, strength increases as the threshold is increased. When filling, strength increases as the threshold is decreased. Separate thresholds are maintained for fill and removal.

The scanner maintains four sets of four binary filter parameters. When scanning, a filter set is selected from the Main Menu or by using the A, B, C, D keypad keys. Each set contains:

Fill Threshold

Removal Threshold

Fill Neighborhood

Removal Neighborhood