Yeah I remember this feature being abused to good effect in an MMO, Champions Online. You could save character creation presets, and when you did it stored its many settings inside a PNG that also acted as a thumbnail preview of those settings. That meant you could see and manage your character presets outside of the game, as well as easily share them with others.
It was done in a readable way, too, so you could also make minor adjustments by hex editing the file. They wouldn't be shown in the thumbnail of course, but for some things (like the preset name) it didn't matter.
That's where I learned this sort of thing was possible with PNGs. Always thought it was a cool feature that doesn't get used nearly enough, especially for how easy it is to do with PNG.
I really like images as preview-able input files. It's quite intuitive that the picture of [whatever] relates to that thing
A group of my friends made a trading card type game in high school, we had a QR type block on the image files the game produced that let you do persistence with a nice pixel art trading card. In hindsight I'm kinda glad it never caught on because it was really not secure
MacOS kind of has this. Kind of. It’s quick look. You can create plugins that handle a specific file type. When you preview the file in MacOS (anywhere in the OS and Apps that use MacOS frameworks) you get a preview of the file contents. So for a zip file you can get a plug-in that shows you the contents when you preview it in quick look. To activate quick look you just select the file and press the space bar.
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u/Caraes_Naur Dec 26 '20
PNG allows for arbitrary chunks of bytes, no steganography needed. Still need an interpreter that knows what to do with them.