Add compress option for save png

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sinisrus
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Joined: Tue Apr 21, 2015 5:43 pm

Add compress option for save png

Post by sinisrus »

Hello,

Is it possible for next release of hollywood to add option compress for save png ?

Thank you

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airsoftsoftwair
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Re: Add compress option for save png

Post by airsoftsoftwair »

Huh? PNGs are already compressed...

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lazi
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Joined: Thu Feb 24, 2011 11:08 pm

Re: Add compress option for save png

Post by lazi »

Some softwares has settings on png compression level 0-9 (PhotoShop, Gimp,...)
AFAIK there is not much gain on file sizes at maximum compression level over the default.

sinisrus
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Re: Add compress option for save png

Post by sinisrus »

I do not agree there is a real gain with compression

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airsoftsoftwair
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Re: Add compress option for save png

Post by airsoftsoftwair »

sinisrus wrote:
Sat Jan 04, 2020 2:38 am
I do not agree there is a real gain with compression
Example please?

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lazi
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Re: Add compress option for save png

Post by lazi »

According to this page https://cimage.se/doc/png-compression-settings
it makes only 1% gain on file size at maximum compression level to the default.

sinisrus
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Re: Add compress option for save png

Post by sinisrus »

Im sorry my picture is saved with PPaint, Hollywood png is ok, sorry !

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lazi
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Re: Add compress option for save png

Post by lazi »

Interesting. As you mentioned PPaint, I checked it and it seems that it is the only program on Amiga which let you set png compression level.

Tried to save the clown.pic example from PPaint in PNG format (compression level default 6) and here is the result:

PPaint PNG (6) - 46272 bytes
PPaint PNG (9) - 46252 bytes

Loaded the file and saved in PNG from ImageFX and Hollywood and here is the interesting part:

ImageFX PNG - 106489 bytes
Hollywood PNG - 102389 bytes

???

And yes, without alpha channel.
The PPaint image is of course 8 bit colormapped, but I thought that PNG works only with truecolor.
So it is a bit tricky how PPaint handle PNG.
This info will be useful if I want to use colormapped images in the future in Hollywood.

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lazi
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Re: Add compress option for save png

Post by lazi »

fxPaint has an option for saving PNG: "reduce to 16 bit"

fxPaint PNG 16 bit: 80426 bytes

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airsoftsoftwair
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Re: Add compress option for save png

Post by airsoftsoftwair »

lazi wrote:
Sun Jan 05, 2020 1:20 pm
The PPaint image is of course 8 bit colormapped, but I thought that PNG works only with truecolor.
No, PNG also supports palette-based images. This explains why PPaint's image is smaller. It saves it as 8-bit whereas Hollywood saves as 24-bit.

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