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5.1.7 IP LUT For the Image Processor Board (7)
When you select option <7>, a display similar to Figure 5-16 will appear. This display is the
Look-Up Table (LUT) for the image processor board. The values in the LUT table are used to
scale incoming pixels before they undergo image processing operations. The first entry is in
Address 00 (top left corner) and the last entry is in Address FF (bottom right corner).
The incoming pixel value serves as the address to the LUT. The value residing at that table
location ( the value looked-up ) is sent through the image processor in place of the incoming
pixel value.
A positive LUT is used for scanning positive documents (dark lines on a light background).
The values looked-up are non-inverted. In the default positive LUT the incoming pixel values
and the outgoing looked-up values are the same:
incoming outgoing
00 00
01 01
: :
FE FE
FF FF
A negative LUT is used for scanning negative documents (light lines on a dark background).
The values looked-up are inverted. In the default negative LUT the outgoing values are binary
complements of the incoming pixel values:
incoming outgoing
00 FF
01 FE
: :
FE 01
FF 00
The <C> command allows you to apply scaling and offset adjustments to the LUT. Two
parameters are required: Step Size and Offset.
• Step Size: This is the value difference between successive table locations. For example, a
step size of 4 will generate the sequence 00,04,08,0C,..
• Offset: Specifies where in the table value stepping begins. For example , if offset is set to
40H in a positive LUT, the first 40H locations are set to zero and the stepping sequence
begins at address 40H.