In most cases in academic publishing a permission is required to reuse (e.g. publish again) previously published graphic content. A problem is that the copyright holder of that content is usually not the artist or scientist who created the original imagery but the publisher. The publisher in turn often requires to pay a substantial fee in order to reuse imagery.
A permission is required if the original image is copied (used as is) or modified (slight changes were made). A copyright is usually NOT required if the image was redrawn (i.e. such substantial changes were made that it can be considered a new work). Most major publishers have this rule in place, see for example a statement by Wiley (link to a .pdf):
Reproduction of a figure means using a figure that has been previously published in exactly the same form. Adaptation of a figure means changing the previously published form, for example by adding or subtracting information. Both reproduction and adaptation of previously published work require copyright permission to have been granted. Redrawn figures do not require copyright permission, nor do figures created using data or results from other publications.
In preparing imagery for academic publications I often trace original images with a vector software, mainly for reasons of quality. A lot of articles publised just a decade ago include graphics of such low quality that upon further printing it would become hardly legible.
Technically I would say that I "redraw" these images (I use an underlying copy to guide my new drawing) but, of course, the end product is basically a high resolution clone of the original image.
Now my question is: Are the terms "redrawn" and "modified" connected to the technique or method used to create a new image or to the difference between the original imagery and the new work? Are there any concrete court decisions on what constitutes "modified" and "redrawn" with a comparison between original and derived image?
I'm asking this question here and not on academia.stackexchange because there are likely more image permission and copyright experts here.