Scanner Acs (Auto Color Selection) - Gestetner B147 Service Manual

2. Twain Mode
Image
Scanning Processing
SBU
After image processing and image compression, the data (TIFF or JPEG) is sent
to the scanner Twain driver directory on the computer.

6.20.2 SCANNER ACS (AUTO COLOR SELECTION)

The scanner auto-color selection (ACS)
function determines if an original is black
and white or color, so that the black and
white mode or the full color mode is
automatically selected.
Comparing RGB video signals, the ACS
processes the original as black and white
if the maximum difference among RGB
signals is within a certain range.
After the above processing, the G signals
are further processed to make black and
white data (a pixel is black or white, not
gray). In this processing, the following
information is compared:
• The G signal level
• The threshold (calculated from the average G signal level)
SM
Image Image
Compression
BCU
6-129
SCANNER FUNCTIONS
I m age
NIB
Controller
Signal
level
R G
P C
B146D927.WMF
B
B146D938.WMF
B147/B149/B190