Images are the main component of the raw information in papers related to image processing. Many of the research papers implement the proposed work on images like Lena, Barbara.

I understand that these are copyright-free images, but sometimes papers use some images that are not well-known but do not mention the source of the image. Meanwhile, some papers mention the libraries from where they have taken the image. Does this depend upon the publication rules?

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    Lena is not copyright-free, but the copyright owner is just not taking legal actions against unauthorized use. en.wikipedia.org/wiki/Lenna
    – silvado
    Commented May 8, 2023 at 7:25
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    In the case of Len(n)a, and perhaps other images, do check out the section Criticism, and the 2019 documentary film Losing Lena.
    – Pablo H
    Commented May 8, 2023 at 14:54
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    Indeed. Just don't use the Lena any more. Commented May 8, 2023 at 22:17

1 Answer 1


If you display an image in your paper or distribute it in some way (like a dump of training data) you need permission to do so from the rights holder. If there's no rights because it's out of copyright, nothing needs to be done. For other content, it may be released under a license that lets you do those things without permission, or you may need to obtain permission individually, which may require payment. The license/agreement will likely also specify if crediting the owner of the image in some way is required.

Regardless of the terms governing image distribution, even if you just use an image without distributing it, you at least need to describe in your paper where you got your materials from. If a paper doesn't do that I'd call it a mistake. If it's peer reviewed then it's a mistake the reviewers missed, otherwise it's just a mistake by the authors. The general standard is that a paper should include enough information to replicate the results.

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    When a legend says "with permission", who's responsibility is it to get that permission? I would imagine it's the author's responsibility, and then the publishers to make sure the permission is actually real. Commented May 8, 2023 at 15:29
  • @ToddWilcox Citation/references are typically for intellectual attribution. Materials and used in a paper are not necessarily referred to in the same way, rather the source is noted in the Methods section, just like equipment or software resources are.
    – Bryan Krause
    Commented May 8, 2023 at 15:48
  • @ScottSeidman I believe authors usually need to sign some agreement that states they own rights to all the images or have obtained permission to use them; I don't know whether it's common for a publisher to "check".
    – Bryan Krause
    Commented May 8, 2023 at 15:50
  • Oh I see. This images are part of the process, not results or data from some other source. I misunderstood the context. Commented May 8, 2023 at 15:50
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    @ToddWilcox Right. If someone compiled a data set of images to be used for a specific purpose, like comparing image processing algorithms, I'd probably cite them like any other paper. If you, say, purchased 10000 images from a stock image repository with the keywords "house" or "face", I wouldn't use the citation/reference format, rather I'd write in the methods section "Training and test images were obtained from Some Company That Sells Images (City, Country)" and explain the keywords used to obtain those images, mention if any special permission was granted, etc.
    – Bryan Krause
    Commented May 8, 2023 at 15:56

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