Select a block that sits on top of something, such as a cover image, a photo or scrolling content. Pick a Backdrop filter just below its background color setting and set the amount. Whatever is behind the block gets filtered, giving frosted glass, dimmed, black-and-white or tinted looks.
The block doesn’t need a background color of its own. Leave it empty to see the filter on its own, or add a semi-transparent color to tint it.
Filters: Blur, Brightness, Contrast, Grayscale, Hue, Invert, Saturation and Sepia.
Blocks that already support backdrop filters natively are left alone. Theme presets referenced as var:preset|backdrop-filter|{slug} are rendered too.
Source code and issues: github.com/jobthomas/glass-act. The editor script in build/ is minified; its unminified source is in src/ in that repository, built with @wordpress/scripts (npm install && npm run build).