[Arnavion]

grim can write the image to stdout. GUI like [1] can read images from stdin. You can make a script that pipes one to the other and bind that in your compositor.

[1]: https://github.com/jtheoof/swappy

[ficklepickle]

You can also use "display" from imagemagick with a pipe. Lots of people probably have that installed already.

[jhvkjhk]

It’s amazing to know pipe, stdin and stdout work for image, thanks!