Krita exports weirdly HUGE pngs when colorspace conversion is involed

I posted this as a bug report before: 459415 – Krita exports weirdly huge pngs when colorspace conversion is involved (kde.org)

But I’m not so sure if it’s a bug at all or if I did something wrong.

For example, I opened this file in Krita, exported it as png with these options:

The result was 2.39MB.

Then I opened the exported file with Windows’ built-in Photos, and saved a copy with it. Now it’s only 767KB.

The 2.39MB file and 767KB file look the same to me.

What’s the hidden thing that Krita embedded in it? I checked “Force convert to sRGB”, so the exported png should have extra colorspace info, right?

Is it, by any chance, a 16-bit file?

Hi

An example of PNG file, exported from Krita and the saved copy could help to understand the size difference…

Grum999

The linked .kra file is 16-bit integer RGB/A.
That file size difference could be explained by the Windows application saving as 8-bit RGB/A with a particular level of .png compression.

A similar .png size reduction can be obtained in krita by converting to 8-bit RGB/A and exporting with an alpha channel.

Oh okay, you’re right. But there is no export option for the 16bit to 8bit conversion…

I know I can convert the colorspace for the whole .kra, but I don’t want it. I want to keep .kra in 16bit linear space and export .png in 8bit sRGB.

I filed a feature request here: An option to export 16bit .kra to 8bit .png - Develop / Feature Requests - Krita Artists (krita-artists.org)

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This request can be merged with Bit depth/color space conversion on export/save as PNG IMO :thinking:

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Yup, it’s been getting rather annoying saving as .png, opening the .png,changing bit depth, then re-saving as .png

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