POV-Ray : Newsgroups : povray.general : [SCC3] Png compression? Server Time
3 Aug 2024 10:23:51 EDT (-0400)
  [SCC3] Png compression? (Message 1 to 6 of 6)  
From: Rafal 'Raf256' Maj
Subject: [SCC3] Png compression?
Date: 28 Feb 2004 03:42:37
Message: <Xns949D62AE7A73Araf256com@203.29.75.35>
Hi,
would it be possible to ask for a .png loseless compresion for some images 
that really need it, instead of jpg qith quality=95? I.e. my image "Borg 
Cube" (.b.i) has totaly messed-up background, since background is 
compilcated blue pattern, and jpg tends to blur blue areas (save this image 
as an .jpg and see the difference - it's quite another image).

-- 
http://www.raf256.com/3d/
Rafal Maj 'Raf256', home page - http://www.raf256.com/me/
Computer Graphics


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From: "Jérôme M. Berger"
Subject: Re: [SCC3] Png compression?
Date: 28 Feb 2004 05:15:13
Message: <40406a31$1@news.povray.org>
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	With the proper settings, JPEG is still a better choice. Take a look at
http://jeberger.free.fr/images/borg_2.jpg which is still half the size
of the original PNG...

	Settings were: 92% quality, floating point DCT, 4:4:4 subsampling (in
the Gimp)

		Jerome

Rafal 'Raf256' Maj wrote:
| Hi,
| would it be possible to ask for a .png loseless compresion for some
images
| that really need it, instead of jpg qith quality=95? I.e. my image "Borg
| Cube" (.b.i) has totaly messed-up background, since background is
| compilcated blue pattern, and jpg tends to blur blue areas (save this
image
| as an .jpg and see the difference - it's quite another image).
|
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From: Rafal 'Raf256' Maj
Subject: Re: [SCC3] Png compression?
Date: 28 Feb 2004 06:08:26
Message: <Xns949D7B676E0E1raf256com@203.29.75.35>
jbe### [at] ifrancecom news:40406a31$1@news.povray.org

> http://jeberger.free.fr/images/borg_2.jpg

Right :) This image is o.k. 
I must stop using IrfanView and switch to Gimp also, thanks.

-- 
http://www.raf256.com/3d/
Rafal Maj 'Raf256', home page - http://www.raf256.com/me/
Computer Graphics


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From: Paul Bourke
Subject: Re: [SCC3] Png compression?
Date: 28 Feb 2004 19:49:13
Message: <pdb_NOSPAM-B26E83.11491229022004@news.povray.org>
> would it be possible to ask for a .png loseless compresion for some images 
> that really need it, instead of jpg qith quality=95?

I you can show there are obvious visual artifacts then I'm prepared to
display it on SCC3 in a better quality jpeg....lossless if necessary.

-- 
Paul Bourke
pdb_NOSPAMswin.edu.au


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From: Thorsten Froehlich
Subject: Re: [SCC3] Png compression?
Date: 29 Feb 2004 06:24:48
Message: <4041cc00$1@news.povray.org>
In article <pdb_NOSPAM-B26E83.11491229022004@news.povray.org> , Paul Bourke
<pdb### [at] swineduau>  wrote:

>> would it be possible to ask for a .png loseless compresion for some images
>> that really need it, instead of jpg qith quality=95?
>
> I you can show there are obvious visual artifacts then I'm prepared to
> display it on SCC3 in a better quality jpeg....lossless if necessary.

Usually there is no need to.  There is a little known fact about the IJGs
JPEG library: By default it always uses 4:2:0 YUV format.  The utilities
that come with it, just like many other programs, do not offer access to the
other widely supported (and specified in the IJGs format) compression
options, which allow each component to be samples at anything from one to
1/16 (i.e. you can have Y values per pixel but U values only for every four
by four pixels and V for every two by two pixels).  And then there is the
RGB format, which also nobody seems to be able to output to.  Yet, all
common decoders I know do support this - they always will if the use the
IJGs JPEG library, which nearly all open source tools use - and will create
still well compressed, but much higher quality JPEG images...

...so essentially one needs to find a tool that allows to make these
settings.  What says Jerome suggests that gimp may be supporting this and
would be the way to go in such a quality problem case.

    Thorsten

____________________________________________________
Thorsten Froehlich, Duisburg, Germany
e-mail: tho### [at] trfde

Visit POV-Ray on the web: http://mac.povray.org


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From: "Jérôme M. Berger"
Subject: Re: [SCC3] Png compression?
Date: 29 Feb 2004 06:57:42
Message: <4041d3b6@news.povray.org>
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|  What says Jerome suggests that gimp may be supporting this and
| would be the way to go in such a quality problem case.
|
	Well, the Gimp doesn't support RGB and only supports 4:2:0, 4:2:2 and
4:4:4 YUV. But that's still better than most software and good enough
for the purpose here...

		Jerome
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