Re: [file2png] Convert (encrypted) binary data to .png images and back

Stefan Claas <pollux@tilde.club> wrote:

Rich wrote:

Stefan Claas <pollux@tilde.club> wrote:

Hi all,
 
here is a Python3 implementation of my file2png program, available
here: https://github.com/706f6c6c7578/file2png
 
Hope you find it useful, when for example uploading such images to
platforms like X, which does not compress .png images, as I have
tested!

 
PNG compression is lossless, so it should not matter if the PNG is
compressed, you should get back the same bytes that went in.
 
Now, if instead you mean "rescale" (reduce/increase size) or other
transformations (RGBI to RGB or RGB to indexed) then those
transformations may alter the content such that you do not get back
what you put in.

 
I remember taht facebook/Meta did something with .png in the past and
it did not work, but it was not rescaling etc.

There's only one compression algorithm in the PNG standard, zlib, which
itself is lossless.

But there are a lot of "transformations" that could be done on a PNG
that would result in modification of the actual image bytes inside. 
Given the potential cost savings to a company with the scale of
facebook/meta from even a few percentage of saved space on uploaded
PNG's from "optimizing" them, it would not be surprising to learn they
were doing something to them that changed the stored bytes.