The idea for this project was shamelessly copied from meskarune's i3lock-fancy.
It uses swaygrab to take a screenshots of every screen, then ImageMagick blurs the image and adds a lock icon and text.
By using information from swaymsg -t get_outputs and basic math, this script supports multiple monitor setups, displaying the icon and text centered on all screens.
The lock icon is different from the original project, with a transparent black circle around it. The text is also an image, making it easier to customize (and to put it at the correct position). Finally, it uses vanilla i3lock instead of i3lock-color. The author of i3lock-color is not maintaining it anymore. If you want to customize the colors of i3lock, the recommended version of i3lock-color is this one, maintained by Chris Guillott.
Make sure you have all the dependencies:
sudo apt-get install sway imagemagick jq
Copy the lock script along with the images to some place on your system (e.g.: the sway folder) and give it execution permission:
git clone https://github.com/sainoba/swaylock-fancy-multimonitor.git
cp -r swaylock-fancy-multimonitor ~/.sway
chmod +x ~/.sway/swaylock-fancy-multimonitor/lock
Create a key binding on your sway config file (in this example I'm using $mod+p):
echo "bindsym \$mod+p exec /home/<your username>/.sway/swaylock-fancy-multimonitor/lock" >> ~/.sway/config
Now reload the sway configuration file. By default, the key binding is $mod+Shift+c.
-n or --no-text: hide the "Type password to unlock" text.
-p or --pixelate: pixelate the background instead of blurring it. Might be faster.