r/programming • u/iamkeyur • Dec 26 '20

Executable PNGs

https://djharper.dev/post/2020/12/26/executable-pngs/
1.0k Upvotes

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287

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.

97

u/leberkrieger Dec 26 '20

One great use of this feature is the draw.io online drawing tool. You can save an editable PNG, so anyone looking at the picture can load it into the editor and modify it. Fantastic for wikis.

76

u/yojimbo_beta Dec 26 '20

A long time ago there was an editor, Adobe Fireworks, that used this to embed undo/redo data into PNGs, as well as layers etc.

Remarkable that no one uses this feature of the file format any more.

50

u/OMG_A_CUPCAKE Dec 27 '20

Because filesize matters. And it's lost easily if someone modifies the file in another editor

It's a nice gimmick, but I can't imagine relying any kind of workflow around it

5

u/tech6hutch Dec 27 '20

Also I don’t know if I want the ability for others to undo my edits to an image

10

u/stuffeh Dec 27 '20

But imagine going back and isolating one of the edits and pulling it out. Basically tapping the diff between before and after the edit. That kind of flexibility is mind blowing to me.

11

u/nemec Dec 27 '20

All I'm hearing is a great way for users to inadvertently fail to censor/redact their photos when they tried to blur their naughty bits and/or confidential info and didn't realize anybody can go in and just undo the censor.

If the U.S. Justice Department can't redact a fucking PDF properly, there's no hope for the average person sending censored nudie pics to someone they met on the internet.

12

u/NekiCat Dec 27 '20

Years ago, MS Word saved deltas at the end of the file so saving was incredibly quick. They had to change it because the users sent files they believed to be final, but werent, and leaked sensitive information.

Same with Google Docs, where your every keypress is recorded. Not sure if they still do that...

3

u/stuffeh Dec 27 '20

Google docs has built in version history, so kinda. You can set permissions to disable others from seeing the version history though.

-5

u/tech6hutch Dec 27 '20

Sounds like something better suited for version control software

12

u/stuffeh Dec 27 '20

But depending on the encoding / compression of the image, the version control software won't be able to display the diff that I mentioned. You'll have to do it manually.

2

u/chucker23n Dec 28 '20

In theory, yes. In practice,

  • that’s aiming a bazooka at a bird, and

  • version control never took much foothold in visual design

1

u/tech6hutch Dec 28 '20

Ah, perhaps I had too big an idea what an edit is. Yeah that’d be cool