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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