Is it plagiarism to copy-paste part of a figure from a cited work? I'm in the process of reviewing a journal submission and noticed that one of the figures is composed of a cropped out piece of a figure from another work. The authors don't cite the figure as coming from this work but do cite the other work elsewhere in the manuscript. Would this constitute as plagiarism?
Yes, copying an image from another work without crediting that work is plagiarism. You may want to contact the editor and ask him how to proceed.