The difference image is often too dark to interpret. Use Process > Enhance Contrast (Saturated = 0.1%) to stretch the histogram. Alternatively, use Add operation with a constant to shift negative values into view.

Have a tricky image comparison scenario? Drop a comment below or check out the official ImageJ forums for macro scripting help.

This is ideal for matching staining intensities across different slides.

These are essential plugins for aligning a stack of images.

Enter . As one of the most powerful, open-source image processing platforms ever created, ImageJ (and its modern derivatives, Fiji and ImageJ2) offers a robust toolkit for image comparison. Whether you need to detect subtle changes between a control and treated sample, validate image registration, or measure the degradation of a material over time, ImageJ provides the quantitative muscle to move beyond subjective "eyeballing."