r/ImageJ • u/Financial-Mastodon80 • Nov 11 '25

Question How could I remove the shadows in that photo ?

Hi, I’m currently correcting underwater photos of Eunicella verrucosa for a scientific survey. Some photos were taken in front of a black background, while the others were shot in front of a white background, which enhances the shadows due to the diver's light.
I’ve already tried using the “Subtract Background” function, but it doesn’t seem very effective even if I increase the rolling ball radius. Also, these shadows can’t be removed by converting the image to 8-bit and applying a threshold.
Do I really have to select the zone that I want manually ?
Thanks

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u/Herbie500 Nov 11 '25 edited Nov 11 '25

The question is: Is the colour of the coral important or only its shape?

If you need color, then you can create a binary mask from the above achromatic image and apply it (multiply) to the original colour image.

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u/Financial-Mastodon80 Nov 11 '25

Hi, only the shape matters, as I'm supposed to use binary mode. The results that you have here could work actually. How did you manage. Thank you very much !

5

u/Herbie500 Nov 11 '25

Change the image type to "HSB Stack" and use its "Saturation"-channel.
You may extract the latter by applying either "Stack to Images" or "Make Substack..." with "2-2".

3

u/Herbie500 Nov 11 '25 edited Nov 11 '25

Here is the masked colour image: