Get Info: #shell

Taking command of the Context Menu in macOS

by Matt Sephton — Tue, 30 Jul 2024 16:14:00 +0000

Yesterday on Twitter the inimitable Morten Just posted a preview of a tool he’s created that wrap ffmpeg to allow movies, such screen recordings but pretty much anything, to be re-encoded to a smaller filesize.

I responded with a trick I use to do the same on “right-click” context menu using a macOS app called ContextMenu, and others said it was possible to do it using Automator (with some caveats). In this blog post I’ll compare the two.

But first… let’s talk about how we will make this work.

Processing files through shell scripts

We’ll be making use of command line tools to do the heavy lifting, but don’t worry I’ll show that this can be as simple as a single-line command to process a single file, or a shell scripts of a few lines to process multiple files.

Single files

The one-line command to convert a video or audio file can be as simple as the following:

/opt/homebrew/bin/ffmpeg -i "$@" "${@%.*}.mp4"

There are some assumptions here:

ffmpeg has been installed using brew
my Mac is Apple silicon, so brew installs commands to /opt/homebrew/bin/
(older Intel Macs will have them installed to /usr/local/bin/)
the script is called with parameters passed by argv so the file is $@
the new file will have the same name as the original, but with a new .mp4 file extension
it only works on single files (read on)

We could add an extra parameter to the command line to use hardware encoding (hevc_videotoolbox) -c:v hevc_videotoolbox, which would be something like twice as fast, but this will not reduce the file size. So we stick with ffmpeg default settings.

You can take the exact same approach with any destination format as it is decided by the file extension. Cool. You could convert any of ffmpeg’s supported file types to any other, such as WAV, OGG, MKV, etc.

And as we’ll see later we can take this simple command and change it to use other command line tools to compress GIFs, with or without upscaling, and many other timesaving tasks. Powerful stuff!

Multiple files

To extend this approach for multiple files you can use the following for loop:

for f in "$@"
do
    /opt/homebrew/bin/ffmpeg -i "$f" "${f%.*}.mp4"
done

Multiple files in parallel

And to process those multiple files in parallel (be careful not to overwhelm your computer!) we can background each execution using the & symbol.

for f in "$@"
do
    /opt/homebrew/bin/ffmpeg -i "$f" "${f%.*}.mp4" &
done

Automator

This has been a built-in macOS app since 2005. Setup is relatively straightforward:

Create a new Quick Action workflow
Workflow receives current: movie files
in: Finder
Add a new action of type action Run Shell Script (search for it in the sidebar)
Pass input: as arguments (this will give us a template command)
Replace the echo line with your command
Save, name it “Duplicate as MP4”

The menu item is now available on the context menu, inside the Quick Actions submenu. After repeated use I find this submenu too annoying, but you may fare better.

So, pretty easy! But, there are some caveats or limitations that may, or may not, annoy you. Perhaps we don’t want the menu item to appear for such a broad range of files (all “movie files”), or maybe we want it to appear for multiple types of files (both “audio files” and “movie files”). Sadly this is not so easy with Automator.

Automator stores these files at ~/Library/Services/ and they will migrate to a new Mac.

ContextMenu

Many years ago I found ContextMenu ($4.99) which solves all of the issues I have with the Automator approach. There’s also a free version, ContextMenu Lite, that supports up to 3 actions to give you a taste of the good stuff.

Submenu is optional
Apply to multiple types (files or directories; can be as granular as file extension)
Show output (sometimes you want to see the results of the command)
Confirmation before running (if it’s a potentially dangerous operation)

The menu item displays in Finder as follows:

ContextMenu stores these files in its own group folder, right click an action and choose Show in Finder, but you can specify your own folder in a location of your choice. Both will migrate to a new Mac, but the later might give you more control.

Edit: we can limit actions to running on files with specific extensions or, since update 1.4.4 specific UTI types.

Compressing a GIF

We can use the gifsicle command line tool to optimise (compress) an Animated GIF. The a parameters I use here are explained in the gifsicle man page, and I arrived at them with years of experimentation.

/opt/homebrew/bin/gifsicle -O1 -Okeep-empty --careful "$@" > "${@%.gif}.o.gif"

We can also do the same thing whilst scaling it up by a factor of 2:

/opt/homebrew/bin/gifsicle -O1 -Okeep-empty --careful --scale 2 "$@" > "${@%.gif}.o.gif"

Repository of ContextMenu Actions

Here’s my repo of shared actions. Inside each .cmaction file is a main.sh file which contains the command that you can use in Automator if you’d like.

github.com/gingerbeardman/contextmenu-actions

These include many useful commands such as:

Convert BIN+CUE to ISO
Change sample rate of audio
Convert image to 1-bit
Convert image format
Create Clean ZIP
Duplicate audio as alternative format
Duplicate image as alternative format
Duplicate movie as alternative format
File information
Generate images for web
Make script executable
Move file (includes helper app)
New file with clipboard
Open file with specific apps
Optimize GIF
Set GIF to loop infinitely
Show GIF info
Playdate Colorize IMG
Replace Existing App (warning)
Scale image to certain percentage
Set as MacJapanese encoding
Show hashes (includes helper app)
Stub out file (warning)
Touch file

Post-processing Animated GIFs

by Matt Sephton — Thu, 16 Jun 2016 00:00:00 +0000

This article was originally posted on pico8 BBS in 2016, and on Playdate devforum in 2020.

I was interested to see how easy/difficult it is to edit the animated GIF recordings. My goal was to trim some frames from the beginning and end to make a more succinct video.

After much trial, error and experimentation here are my findings using Mac OS X.

The game shown in the GIFs is Worm Nom Nom by ilkkke & kometbomb.

Overview

Animated GIFs can be:

viewed frame-by-frame using system Preview.app
manipulated using “gifsicle”, “imagemagick”, “graphicsmagick” command line tools
converted using “ffmpeg” command line tool

Notes

useful tools need to be installed, you may wish to use the “brew” command line tool or similar.

Viewing

Open the GIF in Preview.app and it will show you all frames.
Preview calls the first frame 1 (one), but other tools usually call it 0 (zero).

original/source animated GIF:

Un-Optimising

Warning: If you have previously optimised your GIF to reduce filesize, as in this other thread, and you want to edit the GIF further then be sure to first use gifsicle -U to unoptimise it, otherwise the editing commands won’t work as expected.

Trimming

required: gifsicle

then this is how you trim

gifsicle anim.gif "#212-238" > trimmed.gif

note: this makes a copy of the GIF and keep frames 213 to 239 (gifsicle uses zero based frame count)

Resizing

if you want to double size of the image:

gifsicle --scale 2 trimmed.gif > resized.gif

Captioning

if you want to add an overlay to caption the animation

required: imagemagick or graphicsmagick

then use this bash script:

#!/bin/bash
source=$1
caption=$2
: ${1?"Usage: $0 anim.gif overlay.gif [output.gif]"}
: ${2?"Usage: $0 anim.gif overlay.gif [output.gif]"}

fnsource=$(basename "$source" .gif)
fncaption=$(basename "$caption" .gif)

output=${3:-"$fnsource-$fncaption.gif"}

gifsicle -E $source
for f in *.gif.*; do composite $caption $f $f; done
gifsicle --loopcount *.gif.* > $output
rm *.gif.*

how to run the command

./caption.sh anim.gif overlay.gif [output.gif]

note: if you do not specify an output name, it will be named using original filenames, eg. anim-overlay.gif

overlay.gif

Converting to Video for YouTube

required: ffmpeg

to convert the GIF to MP4:

ffmpeg -i trimmed.gif -movflags faststart -pix_fmt yuv420p video.mp4

video uploaded to YouTube: