From 5b4f601fc74a1ed607fb93fea7cabc4cc3a1f5ba Mon Sep 17 00:00:00 2001
From: Sebastiano Tronto <sebastiano@tronto.net>
Date: Mon, 6 Mar 2023 22:24:32 +0100
Subject: Resized images + blog post

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+# Resizing my website's pictures with ImageMagick and find(1)
+
+I have noticed that most of the pictures I have uploaded on this website
+are incredibly large:
+
+```
+$ du -h -d 1 sebastiano.tronto.net
+42M     sebastiano.tronto.net/gemini
+42M     sebastiano.tronto.net/http
+42M     sebastiano.tronto.net/src
+100M    sebastiano.tronto.net/.git
+225M    sebastiano.tronto.net
+```
+
+Stupid modern phones and their multi-megapixel cameras!
+I definitely do not want my minimalist blog to waste your bandwidth,
+I have to fix this. I could just go through all my pictures and resize
+them with something like [gimp](https://www.gimp.org/) - there are like
+10 of them.  But that's boring. Let's do it with the command line instead.
+
+## ImageMagick
+
+The obvious question is: how do we even edit an image file
+with the command line? Luckily, there is a tool for that:
+[ImageMagick](https://imagemagick.org/). This piece of software
+does a ton of things, and I do not use it very often. So I always
+need to look up what I want to do.
+
+One way to invoke ImageMagick is by calling the `convert` command,
+which can take a
+[`-resize`](https://imagemagick.org/script/command-line-options.php#resize)
+option, followed by a
+[`geometry`](https://imagemagick.org/script/command-line-processing.php#geometry)
+argument. After checking the online manual, I understood that the
+command I was looking for was:
+
+```
+$ convert picture.jpg -resize "750>" picture.jpg
+```
+
+which resizes `picture.jpg` by scaling it down to at most 750px width -
+keeping the ratio between width and height, and leaving it untouched if it
+is already smaller. The value 750 was chosen after a couple of attempts,
+it seems a good compromise between quality and size.
+
+And now I just have to do this for all the pictures. Of course, running
+the same command 10 times with a different argument is out of question.
+
+## find(1)
+
+*(No "man page reading club" this time, but don't
+worry, the series will be back soon.)*
+
+A standard UNIX command, [`find`](https://man.openbsd.org/find) allows
+you to scan a folder for files with certain properties (for example,
+a certain name pattern) and perform actions on them (for example,
+running a command). The OpenBSD and GNU versions of find have some
+differences, check your local manual page. The commands I use
+here have been tested on the GNU version, but should be standard.
+
+To look for file and simply print their name, we can use `-name`:
+
+```
+$ find src -name \*.jpg -or -name \*.png
+src/me.png
+src/favicon.png
+src/speedcubing/cubing.png
+src/blog/2023-01-28-windows-desktop/settings.png
+src/blog/2023-01-28-windows-desktop/tiling.png
+src/blog/2022-09-10-netbooks/darkstar.jpg
+src/blog/2022-09-10-netbooks/final.jpg
+src/blog/2022-09-10-netbooks/scramble.jpg
+src/blog/2022-09-10-netbooks/hd.jpg
+src/blog/2023-02-25-job-control/jobs-diagram.png
+src/blog/2022-12-30-blog-ready/pc-planner.jpg
+```
+
+Now we can use `-exec` to run a command on each of these files,
+using `{}` to refer to the file's name:
+
+```
+find src \( -name \*.jpg -or -name \*.png \) -exec convert {} -resize "750>" {} \;
+```
+
+We get a couple of warnings about grayscale images, but whatever.
+This seems to have worked.
-- 
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