For my reports, this web page and for personal sharing via social media I have used several commands. Why use commands when there are apps, and programs that will do it? Well, I could come up with all sorts of reasons: batch processing, more control (like driving stick), repeatability and so on. But in truth is that I enjoy finding out, and dislike the imprecision of using a mouse. Also it is very probable that most of the apps are using Imagemagick already so it is interesting to go to the source.
The following commands were done on an ubuntu 16.04 or 18.04. Programs like ImageMagick will need to be installed. If you don't have one of these programs installed ubuntu will prompt you to install the correct program (isn't that helpful of an operating system!)
convert -define jpeg:size=2000x2000 IMG_*.jpg -thumbnail 426x213^ -gravity center -extent 426x213 Thumb_*.jpg
Convert all the items that start with IMG and end with jpg to to small centred image file (thumbnail) named Thumb at the begining and extension jpg.
C4AD was registered as a Private company limited by guarantee without share capital Community Interest Company (CIC). In short: not for profit and asset locked. The company's activities will provide benefit to those living in the South West London area and beyond with the use of Science, Technology, Engineering, Arts and Maths. STEM needs Arts to be successful so at C4AD S.T.E.A.M. is promoted: the aim is to demystify STEAM.