I am looking for a small tool that can analyse the average, maximum, and minimum brightness in an arbitrary rectangular region of an image.

It should be able to display a histogram for the selected region, and quickly show which pixels fall over/under a given threshold.

The images will be in bmp format, and monochrome only.

  • preferably a portable program or at least small installation
  • preferably not too many different features. I don't need a photoshop lookalike, this tool only needs to do this one job well.
  • preferably not command line, some small gui to quickly show the results would be nice.
  • preferably free for commercial use, getting an expense approved is such a bother.
  • must run on windows

A big bonus would be if the tool could not only analyse saved images, but also directly overlay results when another programs displays an image on my monitor.

The tool will be used to analyse camera images used for object recognition; to adapt thresholds used by the recognition software after changing camera positions.

1 Answer 1


ImageJ, an image-analysis software. It has a GUI, several interesting features, it's extendable with plugins and it's written in Java, so it works on all platforms.

For your needs, you can drag a selection over an image and interact with that portion (for example, you can see the histogram with CTRL+H, or menu item).

About the "bonus", I never tried it for such feature so you'd better look around the program for it.

  • Yep, the command Image > Adjust > Threshold seems to work nicely for my purposes. As for analzing a life view, it does have a screen capture hotkey at least, so that is a possible workaround. Thanks!
    – HugoRune
    Aug 26, 2016 at 16:21

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