Say there is an image or diagram I want to use from a website. I request permission to use said image. They never respond. Can I use that image in a book I'm writing?
Or do I even need permission if there is no copyright information on the website nor on the image itself? Can I just list the image's website in the appendix of my book?
Also, I have searched on free use image websites like Unsplash. They usually have photographs, not diagrams or functional drawings of the material in my book. So I am specifically wondering about getting images from random .com websites.