Frequently Asked Questions

Is there an OS X version of NIH Image?

ImageJ, which is similar to NIH Image, runs natively on OS X.

Does NIH Image run on a PC?

ImageJ, a Java image processing program similar to NIH Image, runs under Windows. ImageJ is available from In addition, Scion Corporation is porting NIH Image to Windows. You can download a beta version from NIH Image also runs under DOS, Linux, or NextStep using the Executor Mac emulator from Ardi.

Is there a UNIX version of NIH Image?

ImageJ, a Java image processing program similar to NIH Image, runs under most versions of UNIX.

My Mac has 128MB of RAM but the NIH Image About Box shows only 2500K free. Why is that?

You need to allocate more memory to NIH Image. Click (once) on the NIH Image icon (a microscope), select the Finder's Get Info command, and increase "Preferred size".

Why does the desktop change color when I run NIH Image?

NIH Image uses all but two of the 256 available screen colors when the monitor is set to 256 colors. The two "colors" that Image never changes are white (0) and black (255). Objects on the screen that are not black and white are likely to change color when NIH Image is being used. You can avoid this problem by selecting "Desktop Friendly" in Preferences, but this reduces the number of grays displayed to 16. If your hardware supports it, you can also avoid this problem by switching the monitor to "thousands" or "millions" of colors.

Why does text look ragged when I print an image on a laser printer?

NIH Image treats text as if it were part of the bitmapped image. To create high quality text for laser printer output and slide makers you need to export the image to a multi-layer, object-oriented drawing program, such as ClarisDraw or PowerPoint.

In NIH Image, white is 0 and black is 255, which is the opposite of what I'm used to. How can I change this?

Check "Invert Pixel Values" in Preferences. This sets up an inverting density calibration function, causing pixels values displayed in the Info and Results windows to be inverted.

Why does the Paste command sometimes get dimmed out?

Images copied to the clipboard are stored in the Clipboard buffer. In some situations, such as filtering, NIH Image has to use the Clipboard buffer for internal operations. When this is happens, the Paste command gets dimmed out.

How can I create a composite color image?

You can't normally combine two images that have different LUTs, but if you check "Keep LUT" when you open the second image (which must be stored as a PICT file) its pixel values will be remapped to conform to the LUT of the first image. You will then be able to successfully Copy and Paste, since both images have the same LUT.

How can I convert a stack to a QuickTime movie?

NIH Image 1.61 and later can save a stack as a QuickTime movie.

Is there any help in understanding densitometry and/or gel analysis?

There are a number of documents available explaining anything from portions of the theoretical principles of densitometry, to step by step help in using the gel analysis macros. Those interested in densitometry should strive to understand the "Calibrate" command and why it is used.

For explanation regarding basic underlying principles of densitometry read the section of Image Engineering on Fundamentals of Densitometry. For a simple explanation on the Calibrate command, see the Calibrate section of the NIH Image manual. For basic step by step explanation on the gel macros, read the Analyzing Electrophoretic Gels section of the NIH Image manual.

Calibrated optical density step tablets are made by Kodak and sold through as described by this page:

How should I cite NIH Image

Published research assisted by NIH Image should use a statement similar to the following in the materials and methods section "... analysis performed on a Macintosh computer using the public domain NIH Image program (developed at the U.S. National Institutes of Health and available on the Internet at".

Is there an NIH Image Home Page?

The NIH Image home page provides on-line documentation, links to download the software, tutorials, links to other image processing software, an archive to search for answers to questions and more. The NIH Image home page is located at:

How do I download NIH Image?

The latest version of NIH Image, documentation, source code, macros and more can be downloaded by going to NIH Image Home Page and following the "Download" link.

Is NIH Image Year 2000 compliant?

All versions of NIH Image are Year 2000 compliant. The GetTime macro command, the only function that deals with dates, returns a four digit year.

Is the "G3" digitizer supported?

NIH Image's Start Capturing command does not work with the G3 Mac's built-in digitizer. You can, however, use the Plug-in Digitizer available from

[NIH Image Manual]
[NIH Image Home Page]