20/02/2023 ⚠️ this update will remove your local config files (aspect_ratios.txt and resolutions.txt) and it will create new default ones. These can be then modified freely and preserved in the future. For more info read here.

Install

Browse to the Extensions tab -> go to Install from URL -> paste in https://github.com/alemelis/sd-webui-ar -> click Install

Here's how the UI looks like after installing this extension

Usage

Click on the aspect ratio button you want to set. In the case of an aspect ratio greater than 1, the script fixes the width and changes the height. Whereas if the aspect ratio is smaller than 1, the width changes while the height is fixed.
Reset image resolution by clicking on one of the buttons on the second row.

Configuration

Aspect ratios can be defined in the /sd-webui-ar/aspect_ratios.txt file. For example,

1:1, 1.0
3:2, 1.5
4:3, 1.333
16:9, 1.777
# 6:13, 0.461538
# 9:16, 0.5625
# 3:5, 0.6
# 2:3, 0.666
# 19:16, 1.19 # fox movietone
# 5:4, 1.25 # medium format photo
# 11:8, 1.375 # academy standard
# IMAX, 1.43
# 14:9, 1.56
# 16:10, 1.6
# 𝜑, 1.6180 # golden ratio
# 5:3, 1.6666 # super 16mm
# 1.85, 1.85 # US widescreen cinema
# DCI, 1.9 # digital imax
# 2:1, 2.0 # univisium
# 70mm, 2.2
# 21:9, 2.370 # cinematic wide screen
# δ, 2.414 # silver ratio
# UPV70, 2.76 # ultra panavision 70
# 32:9, 3.6 # ultra wide screen
# PV, 4.0 # polyvision

Note the # marking the line as a comment, i.e. the extension is not reading that line. To use a custom value, un-comment the relative line by removing the starting #. A custom aspect ratio is defined as button-label, aspect-ratio-value # comment. The aspect-ratio-value must be a number (either float or int) while the # comment is optional. The button-label will be displayed inside the button. It can be anything you like.

Resolutions presets are defined inside resolutions.txt file,

1, 512, 512 # 1:1 square
2, 768, 512 # 3:2 landscape
3, 403, 716 # 9:16 portrait

The format to be used is button-label, width, height, # optional comment. As before, lines starting with # will be ignored.