The AIJ installation packages starting with the (updated) v3.2.0_2017022_windows_java7_x64 and x32 zip installation files and later (i.e. the packages with Java included) are now compatible with Windows 10 high DPI screen scaling (if you reinstall v3.2.0, be sure to use the AIJ update feature to get back to the latest version after the re-installation).
If you instead configure AIJ to use a custom installation of Java on your machine (i.e. not the one in /AstroImageJ/jre directory), you will need to use a program such as "Resource Tuner" (http://www.restuner.com/
; which as of now offers a 30 day free trial period) to edit the manifests for the java.exe and javaw.exe executables in your java installation's /jre/bin directory to change the dpiaware entry from true to false:
Updating to a later AIJ build will not affect this setting, but updating your own custom Java installation will likely revert to the original setting.
This solution was provided by an AIJ user (Thank you Thomas!) and is based on the information at this stackoverflow link: