In many cases, linking together existing functionality using macros is insufficient for a necessary application and users need to add new functionality. In 1993, Rasband saw the great utility of plugins being used by Adobe Photoshop (Adobe Systems Incorporated) to add new functionality to that software and decided to add these modular software elements to NIH Image. NIH Image was one of the first scientific imaging processing tools to have plugins and the first with such a large user base. Example plugins included facilities for 3D rendering of images and particle analysis. ImageJ has had plugin support from its inception and plugin numbers have increased rapidly, with over 500 plugins covering a wide range of functions available on the ImageJ website (Figure 2). Many of these plugins are now distributed with the core ImageJ. Rasband’s philosophy of limiting complexity drove how he decided what functionality to integrate into the program directly or distribute as plugins. Many of the plugins built into ImageJ are from outside contributors and the decision to include a plugin in the base distribution was based on whether Rasband thought it would have widespread use.
