vipsdisp

I made an image viewer for large images: https://github.com/jcupitt/vipsdisp It should be fine with your huge PNGs. Internally it's a bit like a tiled map viewer, but it makes the tiles as you view the image with a set of background worker threads. It uses your GPU to scale and composite the set of visible tiles to your screen. It uses openslide to let you view slide formats like SVS and MRXS, which might be handy. It also supports colour management.

Yes, I based it partly on visual programming system that Canon made back in the 90s. I loved the interactive development, but I really disliked that style of visual programming. Lines between boxes seems very hard to reason about, to me. nip2 tries to do something similar, but using expressions, like a spreadsheet. Unlike graphical plugs and wires, expressions allow things like copy-paste, smart refactoring, referential transparency, and progressive rewriting. nip2 is ancient now (I finished it way back in 2002, I think). I've started a rewrite for gtk4 -- the image display window is here: https://github.com/jcupitt/vipsdisp It's quite fancy -- it has a sparse pyramid of image tiles which get composited to your display by the GPU, and computed asynchronously by a libvips pipeline as you zoom and pan around. You should get a smooth 60 fps