FAQ: What is ImageJ?
General first user information regarding ImageJ.
ImageJ is an image processing and analysis program written in Java by Wayne Rasband at the U.S. National Institutes of Health
The source code is freely available from the ImageJ website.
ImageJ can be run as an online applet, servlet, or a downloadable application on any computer with a Java 1.1 or later virtual machine (ImageJ 1.38a requires Java 1.4.2 or later).
The program functionality can be expanded using a macro scripting language and via plugins written in Java.