Useful imaging handeling and analysis software that can be freely downloaded.
Fiji: An image processing package. It can be described as a distribution of ImageJ together with Java, Java 3D and a lot of plugins organized into a coherent menu structure. Fiji compares to ImageJ as Ubuntu compares to Linux. The main focus of Fiji is to assist research in life sciences.
QuPath: A powerful freeware for digital pathology analysis and biomarker interpretation.
CellProfiler: Free open-source software designed to enable biologists without training in computer vision or programming to quantitatively measure phenotypes from thousands of images automatically.
Photopea: A free image editor with Photoshops functionalities and appearance. It runs directly in a web browser.