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Add compress option for save png

Posted: Thu Jan 02, 2020 5:49 pm
by sinisrus
Hello,

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

Thank you

Re: Add compress option for save png

Posted: Fri Jan 03, 2020 9:44 pm
by airsoftsoftwair
Huh? PNGs are already compressed...

Re: Add compress option for save png

Posted: Fri Jan 03, 2020 11:29 pm
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.

Re: Add compress option for save png

Posted: Sat Jan 04, 2020 2:38 am
by sinisrus
I do not agree there is a real gain with compression

Re: Add compress option for save png

Posted: Sat Jan 04, 2020 9:12 pm
by airsoftsoftwair
sinisrus wrote:
Sat Jan 04, 2020 2:38 am
I do not agree there is a real gain with compression
Example please?

Re: Add compress option for save png

Posted: Sat Jan 04, 2020 11:59 pm
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.

Re: Add compress option for save png

Posted: Sun Jan 05, 2020 1:46 am
by sinisrus
Im sorry my picture is saved with PPaint, Hollywood png is ok, sorry !

Re: Add compress option for save png

Posted: Sun Jan 05, 2020 1:20 pm
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.

Re: Add compress option for save png

Posted: Sun Jan 05, 2020 1:27 pm
by lazi
fxPaint has an option for saving PNG: "reduce to 16 bit"

fxPaint PNG 16 bit: 80426 bytes

Re: Add compress option for save png

Posted: Sun Jan 05, 2020 1:58 pm
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.