Let's say I have an open source image. I create a larger image by pasting it together with a load of other images that I own. Now I use a computer program to calculate a number, which represents the average level (brightness) of the combined image. Does that number count as a derivative work?

Intuitively this seems ridiculous, as almost no information contained in the original image is transmitted to the number, and therefore there is no "copy". The letter of the law though seems to say that it might be derivative. Thoughts?

I want to write a report which documents the computer program, but I'm worried that because it uses such numbers as part of the analysis, I'll have to open source the whole thing.

  • I assume by "open source image" you mean in particular an image under a copyleft license like CC-BY-SA, correct? If the license isn't copyleft, then even in the worst case for you (the aggregate data is a derivative under copyright) the terms of the license need not extend to your whole report.
    – apsillers
    Oct 5, 2017 at 12:10

1 Answer 1


Most open source and free culture licenses (such as the GPL licenses or the Creative Commons licenses) are based in copyright law. They cannot prevent uses that do not violate the copyright of the original work. Copyright only protects a particular creative expression.

A work is a derivative work if it contains the creative expression of the original work in parts or in whole. E.g. your image that is a collage of multiple images is a derivative work of all source images. You cannot publish your image unless you have a suitable license for all source images, or are eligible for a copyright exemption under your local laws (e.g. fair use in the U.S.).

However, facts and ideas are not protected by copyright. They may be protected by other legal constructs (e.g. trade secrets, patents, database laws, sui generis rights, or private contracts), but open source/free culture license do not include such restrictions. Without such non-copyright restrictions, you are free to use any information from copyrighted works. So given an image, you are allowed to state facts about it (e.g. “white background”, “280px wide”, “depicts a donkey”) and are allowed to create your own work that references the image (e.g. publish a video inspired by the image, or write an in-depth analysis of the composition and artistic techniques used in the image).

So I'm pretty certain that publishing an analysis of the average brightness of an image violates neither the copyright of the original image, nor the copyright of the computer program used to perform the analysis.

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