PNG file size.

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borgo1971
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PNG file size.

Post by borgo1971 » Fri 22 May 2020 21:34

In the last times, I've noticed a strange behaviour while saving PNG files from my MacBook: the size of the files are much bigger than what calculated on preview. The files I'm talking are small for itself, about 800x600 pixel, but in preview PhotoLine calculate about 45 kB, but then the saved file results in about 160-180 kB. The strange thing is that saving the same file with MacPro, as I can see with the same settings, produce really a 45 kB file. And the same behaviour happens with PhotoLine 19.51 that I use normally (on both computers), and even with PhotoLine 22 that I downloaded to make some tries about this strange behaviour. I tried to attach some screenshots from MacBook, file saved with MacBook and PL 19 and 22, and the same file saved with MacPro, but while I continue to get error messages because the file are to large (even all 6 images together are less then 700kB and in a 7z archive are less then 500kB), i put them on dropbox and if someone want, can download the archive from this link: https://www.dropbox.com/s/gxmq1njgdxbhk ... so.7z?dl=0
It's not a blocking problem, more a curiosity for this strange behaviour... I guess something that continues to elude me.

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Herbert123
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Re: PNG file size.

Post by Herbert123 » Sat 23 May 2020 04:03

The MP PL19 png file is saved as an indexed 256 colour version, while the other two are not (true colour each having 1326 colours). So that explains the difference in file size.

Have you tried using the web export option to force 256 or less colours when saving to a PNG file?
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System: Win10 64bit - i7 920@3.6Ghz, p6t Deluxe v1, 48gb (6x8gb RipjawsX), Nvidia GTX1080 8GB, Revodrive X2 240gb, e-mu 1820, 2XSamsung SA850 (2560*1440) and 1XHP2408H 1920*1200 portrait

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Herbert123
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Re: PNG file size.

Post by Herbert123 » Sat 23 May 2020 04:11

PS that file can be optimized even further with no loss of visual quality by reducing the number of colours to 48, or so.
This one is only 32.8kb.
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/*---------------------------------------------*/
System: Win10 64bit - i7 920@3.6Ghz, p6t Deluxe v1, 48gb (6x8gb RipjawsX), Nvidia GTX1080 8GB, Revodrive X2 240gb, e-mu 1820, 2XSamsung SA850 (2560*1440) and 1XHP2408H 1920*1200 portrait

bkh
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Re: PNG file size.

Post by bkh » Sat 23 May 2020 09:10

Looks like there is a bug in PL. In the preferences, you have checked "chiedi" (ask) to ask for file compression settings before saving.
PNG settings MB ann.png
On my system (macOS 10.15.4, PL 22.02), PL doesn’t put up a confirmation dialogue but saves the file without colour reduction. If you uncheck that option, colour reduction works as expected.

Cheers

Burkhard
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borgo1971
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Re: PNG file size.

Post by borgo1971 » Tue 26 May 2020 15:38

Thanks. True, the "ask" check was the guilty. I didn't really realize when I checked it, but didn't notice it because I didn't guess it will have to do with strange behaviour. If you asked me about it, without seeing the settings on both my computers, I think I guessed to have it enabled on both, and that unchecking it will hide options in save dialog.
Sorry I didn't respond before, I guessed (ok, to much guessing) I enabled notify for reply, and was waiting for it.
The goal was not really optimize more this file, but to understand way it won't at all...
Thanks to all for answering.