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Hello, today using a hex editor I took a look at the binary .pur file format of a file with a single image. In there I found where the .png is stored.
I decided to cut away all the bytes in front and after that .png for fun, rename the corrupt .pur to a .png and you can open it in an image viewer as if you exported it.
The 500x500 .png that it resulted is slightly smaller than the .pur. The .png being 148.7kB and the original .pur being 149.5kB.

But when you open the original .pur and export the image the resulting .png is... 751kB?!?!?

Exporting the image in krita with a png compression of 1 gives you a 191kB image.
Exporting it with a compression of 9 gives you a 140kB image.
When I exported it with a .png compression of 7 I got 148.7kB which is very similar to the image I ripped out with the hex editor so I suspect you use a compression rate of 7 which is a nice balance.

You are already using .png compression so why don't you use it in the exported .png? Or just dump the .png that is already in the .pur like I just did manually? For larger images this inefficiency becomes even more horrible.

If you don't want to do this I'd gladly fix it for you if you gave me the source code. Sorry if you don't like people reverse engineering your format.

Edited 1 time(s). Last edit at 2022-08-14 21:20 by BeetRoot.
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