User`s manual

Setting the Conditions for Each Object Type
3-23
3
(2) Gray level change
To change the gray level, you can change the
"**.*TIMES" (magnification by N processing), the
"
γ
+," "
γ
-" (
γ
(positive/negative) correction), the
"CHNG-L" (widening histogram), and the "INCRS-
M" (mid emphasis) functions.
Details
Gray level change
Magnification by N
processing
(**.* TIMES)
g
(positive/negative)
correction
Histogram
widening
Mid emphasis
To improve the contrast (the ratio of high value gray levels to low value gray
levels), specify a magnification rate (00.0 to 99.9) for multiplying the image
data.
- If the magnified gray level exceeds 255, the system will correct the value
to 255.
- g positive correction: used when the mid gray level is too low.
255
255
Input image gray level
Output image gray level
255
255
Input image gray level
Output image gray level
- g negative correction: used when the mid gray level is too high.
This is a method to widen the histogram of an image in which the histogram
is at part of it, thus improve its contrast.
Emphasize the mid gray level.
- This improves contrast while remaining the background image.
- The input image density (G) can be converted to the output image density
with the following formulas:
0
Z m
a
b
0
Z m
2 Good contrast image
Gray level Gray level
1 Bad contrast image
0 to 127
128 to 255
（Ｇ÷127）
2
×127
（（Ｇ−128）÷127×127）＋127
Output image gray level
Input image gray level(G)
1
COMPARE IMGS NO
2
CHNG GRAY LEVEL NO
3
SPACE FILTER NO
IMG PRE-PROC SCREEN COND SAVE F C1 BRT
NO
CONTRAST MAGNI
+
-
CHNG-L
INCRS-M