Images for talks and illustrations

I promised in January to list websites where you can find free images ( free as in beer and free as in speech  ). And then I forgot about the promise. Since I mostly use Inkscape  to draw illustrations, I normally search for SVG images. Inkscape is an open-source software that generates vector graphics. SVG is not only the web standard for vector graphics but also the native file format for Inkscape. Sometimes, PNG or JPEG images are also acceptable if they can be easily converted into SVG images (e.g., silhouettes). Occasionally, I look for 3D images (“models”), and then I prefer them in Blender  format (the only 3D software that I have used more than just a few times).There are two different types of free images on the web: Public Domain  and Creative Commons  . Public Domain images can be used without restrictions, while Creative Commons images typically come with some restrictions. The most common restriction for CC-licensed images is that you need to credit the creator. Sometimes, there are additional restrictions, such as prohibiting commercial use or modifications.When you do an image search with Google  or DuckDuckGo  , you can restrict the view to images that conform to a specific license. However, Google and DuckDuckGo cover only a fraction of the internet, and there are search sites that have specialized in searching for specific images.You may also ask AI to generate the perfect image. It typically requires several iterations to get something useful, and you will never be able to get copyrights for the image, even though you spent hours engineering the perfect prompt. You can try e.g., DALL·E 3  , or you can even run some AI image generators on your own computer like Stable Diffusion  . The image above was generated with DALL·E 3, using the following prompt: “A person surrounded by images, symbolizing the search for the perfect image.”

• https://search.creativecommons.org/  (a meta-search portal that searches many image repositories that host CC-licensed images)
• http://phylopic.org  (silhouettes of animals, different licenses)
• https://thenounproject.com/  (icons and images)
• https://www.svgrepo.com/ 
• https://commons.wikimedia.org/wiki/Main_Page  (CC-licensed images; I make some of my images and illustrations available via Wikimedia: https://commons.wikimedia.org/wiki/User:Mjeltsch  )
• https://papunet.net/kuvatyokalut/kuvapankki/  (CC-licensed images)
• Another good source of scientific illustrations are journals that publish Open Access articles. These are usually CC-licensed, and most of the images in these articles are CC-licensed as well (not all, so be careful! It is allowed to use non-CC-licensed images in a cc-licensed article) 3D models https://www.turbosquid.com/Search/3D-Models/free 
• https://sketchfab.com/tags/free 
• https://3dwarehouse.sketchup.com/ 

Image repositories exclusively hosting Public Domain images

• https://stocksnap.io/ 
• https://www.pexels.com/ 
• http://negativespace.co/ 
• http://cupcake.nilssonlee.se/ 
• https://www.everypixel.com/free  (this one claims to do a meta-search on all other PD-only image sites)
• Image repositories with their own license (close to Public Domain) http://www.lifeofpix.com/ 
• https://unsplash.com/