Dividing two pictures from each other

Dear all,

I am very new in ImageJ and I really need your help. I searched in the manual and I did not really find a good solution.

I have two pictures and both look a little bit like this (more or less):

Now I want to divide one picture from the other picture, so I can see where the value is 1 and 0 (and between).

Thanks a lot for your help and all your efforts


I am not getting the task.
You want to divide the image in how many images? and where do you want to divide?
Thank you,

Do you mean thresholding? Use the Image :arrow_forward: Adjust :arrow_forward: Threshold… command (shortcut Shift+T). The Auto Threshold plugin is also useful for comparing thresholding methods.

To convert your threshold to a binary image, click the Apply button.


I guess you mean that you want to divide one image by the other. If this is true, you should have found the description of “Process > Image Calculator…” in the ImageJ-manual – no?



@emartini Let us say, white is 1, black is 0 and the grey colours are something between 1 and 0. Now I have one picture before something happend and one picture after something has happend. So I want to devide the first picture through the second picture.

@ctrueden No, not really thresholding. I have one substance, which I have measured and an internal standard for a quantification. Maybe the discription above is good. If I have at both pictures the value 1, both substances have the same concentration and so on. I hope you might understand it better now.

@anon96376101 I will try it in the next minutes and I will keep you updated, if you are right. At first, it really sounds pretty good. Sorry, that I have not found it. Actually, I was not really show what I have to search for.

Thank you all!!! :smile:

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oh ok Ralf, I have completely misunderstood … I thought that you will to subdivide your image in many images :wink:

by the way I think like @anon96376101 that Image calculator in Process menu will do the job you are asking;)
See you,
have a nice day

Hi Ralf,

Could you find a solution to your problem? I´m having the same and the suggestions don´t really help.

According to your picture you have lots of dark background (same in my case). When I use the function Process -> Image calculator -> Divide, I get a completely saturated image, with the area of interest (in your image the white “lines”) not visible. This happens, because the black background still has low grey values. When you then divide these low values you will get a significant noise in your image. I could not get rid of the problem by changing brightness or contrast.

I guess it would be possible if the dark background could be set to zero somehow?

Appreciate your help, thanks.

Sorry for the long delay in reply, @Johannes_G!

Did you check the “32-bit (float) result” option? Without it, division will typically have insurmountable rounding errors.

You can do that by thresholding (shift+T), then Create Selection (press L for the Command Finder to run it) and finally Clear Outside.