IBM CF Series manual IP LUT For the Image Processor Board

5.1.7IP 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.