I have multiple pictures that are look alike, they're all black and differ only in the one dot of the screen, I want to combine them in one picture so I can see all the dots in one picture. How can I do this using something like ImageMagic? I don't want to use something with gui bc there are a lot of pictures, but they're not that big, so it would be easier to do this with terminal utility. I tried

composite -blend 50 *.png res.png

but it didn't work out.

UPD: Now I understood that it doesn't work because it works only with two images, how do I do these to all the images that matches the regular expression like somth*.png?

  • "didn't work" is a poor description. All it conveys is you could not achieve your goal. Please describe precisely what happens when you try that command.
    – Quasímodo
    Oct 10, 2020 at 14:57
  • It shows only the last dot, I guess, and not the others, at least I can't see them
    – Arzybek
    Oct 10, 2020 at 14:59
  • Is unix.stackexchange.com/q/329886 of any help?
    – Quasímodo
    Oct 10, 2020 at 15:18
  • Not really, because it's not the problem to do many files, the main problem is how to overlay them correctly
    – Arzybek
    Oct 10, 2020 at 15:26
  • for blending, is there a logic function available, such as OR or AND? ... perhaps, convert black to transparent
    – jsotola
    Oct 10, 2020 at 15:48

1 Answer 1


You need the Screen compositing method.

Since the composition only accepts two input files at a time, loop over all the input files.

Substitute somth1.png below by any of the input files. It is needed because res.png is always a starting point.

cp somth1.png res.png 
for f in somth*.png;
    do composite -compose Screen "$f" res.png res.png

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