NIH Image: An Introduction and Tutorial

This on-line tutorial is based on the paper "NIH Image: A Public Domain Image Processing Program for the Macintosh" by Wayne Rasband and David Bright, published in Microbeam Analysis, 4 (1995).

NIH Image can acquire, display, edit, enhance, analyze, print and animate images. It reads and writes TIFF, PICT, PICS and MacPaint files, providing compatibility with many other applications, including programs for scanning, processing, editing, publishing and analyzing images. It supports many standard image processing functions, including contrast enhancement, density profiling, smoothing, sharpening, edge detection, median filtering, and spatial convolution with user defined kernels. A series of images can be animated or viewed in a stack. Particles can be counted and sized. NIH Image can be customized using a Pascal-like macro programming language and through use of plug-in code modules.

NIH Image comes with many other files: a user manual ("NIH Image Manual"), a programmer's guide ("Inside NIH Image"), a folder of convolution kernels, and a folder of macros.

MacLispix, described in an accompanying article in this issue, is another public domain image processing program for the Macintosh, which does some of the same things but in different ways. MacLispix is not as polished a Macintosh application as is NIH Image, but is intended for more special purpose analyses such as three dimensional scatter diagrams, principal components and chemical phase analysis, and for instances where more numerical precision than 8 bits per pixel is needed.


NIH Image conforms well to the Macintosh user interface standard, and is visually and graphically oriented, making it easy to use with little experience. For example, NIH Image has a palette of tools for drawing, measuring and examining images which are fully described in "About NIH Image". A variety of measurements can be made on user-specif ied regions of interest and results exported to a spread sheet or plotting package. The "LUT" (color look up table) and "Map" windows allow control of the video lookup table, providing flexible contrast enhancement and false color. The "Info" window displays cursor position, pixel values, selection size, line length, etc. Images, look-up tables, macros and convolution kernels can be opened by dragging them to the NIH Image icon.

System requirements

NIH Image requires a Mac II or later with 8 MB or more of RAM. (Running NIH Image on a 4 MB Mac is a struggle.) System 7 or later is also required for versions 1.56 and later (because of the plug-ins and 24-bit to 8-bit color conversion), and for many of these examples. A Power PC native version is available as well as a non-FPU version for Macs without a floating-point co-processor.

NIH Image Users

There is an active electronic mailing list on the Internet with over 1000 subscribers and a dozen messages or so a day covering topics such as a) news of the latest versions of NIH Image b) special purpose macros c) image processing tips using NIH Image d) hardware - frame grabbers e) bugs, wish list items. Subscribe to the list by sending the one line message "subscribe nih-image <first name> <last name>" to

The user base for NIH Image is large: over two thousand copies of v1.55 alone have been downloaded from the NIH Image FTP site.


( The actual steps begin with bullets.)

These examples are meant to be cook-book type lists that can be followed by a new user to get started. Menu commands are shown in italics, for example, File - Open is the Open command in the File menu.

Starting up and configuring