Gitignore - Ignore only images & ignore everything except .. in single command

Question

How can I write to .gitignore:

1. to ignore only images ( .jpg, .jpeg, .png, .gif )

2. to ignore everything except videos ( .mp4, .flv etc )

Answer 1

1 Ignore images

printf '*.jpg\n*.jpeg\n*.png\n*.gif\n' >> .gitignore

2 Ignore everything but videos:

See How do I tell Git to ignore everything except a subdirectory?

printf '*\n!*.mp4\n!*.flv\n' >> .gitignore