Adds a note for an imagemagick command that resizes and optimizes.

src/content/notes/NixOS/Useful Utilities.md

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+---
+title: Useful Utilities
+---
+
+Here's a small collection of various utilities and recipes I find useful. It's not organized in a particular way, but more as a long-term memory for me.
+
+## JPEG Optimization
+
+[jpegoptim](https://github.com/tjko/jpegoptim) is a handy little utility for doing JPEG optimization. I use it to compress files and strip EXIF data. Here's an example that will process all the files in the current directory and compress them to a reasonable 85.
+
+```bash
+nix run 'nixpkgs#jpegoptim' -- --max=85 --strip-all *.jpg
+```
+
+The major issue with `jpegoptim` is that it doesn't do resizing. Image Magick is the Swiss army knife of image manipulation and can do it all, but it's a much larger piece of software. This can quickly reduce a full-size camera image (~5MB) to something suitable for web uploads, thumbnails or avatars (50kB).
+
+```bash
+nix run 'nixpkgs#imagemagick' -- input.jpg -resize 1200x800 -strip -quality 85 output.jpg
+```
+
+There are lots of options that can be passed to the [image geometry](https://imagemagick.org/command-line-processing/#geometry). The default for pixel sizes is to treat it as a maximum and preserve the aspect ratio. If only a width is given then height is automatically determined from the aspect ratio.