Allows to optimize contrast by selecting a lower and upper threshold value.
The dialog box displays a histogram of gray levels. The upper and lower threshold values are represented by vertical red lines.
You drag the red lines to the required threshold values.
- pixels with a gray value less than the lower threshold value will be black.
- pixels with a gray value higher than the upper threshold value will be white.
- the gray values between the two threshold values will be stretched over the full range of possible gray values.
Click Preview to judge the results.
Click OK to proceed.