Summary Of Image Processing Functions - Gestetner B003 Service Manual

6.5.6 SUMMARY OF IMAGE PROCESSING FUNCTIONS

1. Shading correction. Compensates for the possible differences in the amount
of light at the edges and center of a scanned image caused by the scanner
lens, or scatter among pixels of the CCD.
2. Black line correction. Attempts to compensate for black lines in copies
caused by dirt on the exposure glass of the optional sheet-through document
feeder.
3. Background erase. Attempts to eliminate the heavy background texture from
copies of newspaper print or documents printed on coarse paper. Elements
below the selected threshold level are eliminated.
4. Smoothing. Attempts to reproduce halftones with simple, parallel smooth
processing. Smoothing the image density reduces the incidence of moiré, but
also reduces sharpness.
5. Main scan magnification. Adjusts magnification to the desired level by
processing adjusting multiple, adjacent pixels in the direction of main scanning.
(Adjustment of magnification in the sub scan direction is done by changing the
scanning speed.)
6. Independent dot erase. Attempts to recognize and eliminate scattered,
independent dots in copies. Processes only pixels of high density and
eliminates those of low density.
7. Filtering (MTF filter/smoothing). Performs mainly edge enhancement with the
MTF filter. Performs smoothing only in the photo mode. The matrix size of the
filter is 9 pixels x 7 lines.
8. Gamma (γ γ γ γ ) coefficient. Controls the image density for images processed with
grayscaling. Copy density adjustment is achieved with special notch γ
coefficient conversion. The best γ coefficient suited for the selected mode can
be stored and adjusted as needed.
9. Grayscale processing. Performs reproduction of grayscales, using mainly
error diffusion. (In the photo mode, conducts processing with dithering.)
SM 6-21
IMAGE PROCESSING
B003/B004/B006/B007