"Utilities->Stretch" is a tool to stretch the pixel values of the input file to a user-defined interval.
Output Min:
The minimum value of the output file.
Output Max:
The maximum value of the output file.
Customize:
Enable/Disable the "Input Min" and "Input Max".
Input Min:
If the value of a pixel is smaller than the threshold, the value of the pixel will be set to "Output Min"
Input Max:
If the value of a pixel is larger than the threshold, the value of the pixel will be set to "Output Max"