Calculate contrast ratio for readability based on WCAG 2.0 recommendations. If
you have grabc installed, you can also capture color from your screen by
clicking on the color preview.
This extension has been tested on gnome-shell 3.26 and 3.28. If you're using this extension in earlier versions of gnome-shell, please let me know so I can officially add it to supported versions.
If you want to capture color from a pixel on your screen, install grabc
apt-get install grabc
Now you can grab a hex color code from a pixel on your screen by clicking on the color box beside either the background color or text color.
You can install contrast ratio from gnome extensions: https://extensions.gnome.org/extension/1430/contrast-ratio/
git clone https://github.com/larissa/contrast-ratio.git ~/.local/share/gnome-shell/extensions/contrast-ratio@amadteaparty.org
Restart the shell and then enable the extension.
Picking a color from anywhere on screen is not supported on wayland for
security reasons, so grabc (and any other color picking tool) won't work if
you're using wayland.