If you're into Digital Pathology and Whole Slide Image (WSI) analysis then there is a whole undergrowth of open source tools and projects to dive into. I especially like QuPath by Pete Bankhead (https://qupath.github.io/). It has a more accessible interface than python (as in the article), it supports various machine learning algorithms and also has some nice video tutorials (https://www.youtube.com/channel/UCk5fn7cjMZFsQKKdy-YWOFQ).
Tumors? Dark spots?
And on what type of media? Xrays? MRIs?