[Tig] Fwd: [CinePaint] jpg worse
rob at colorist.org
Fri Mar 14 20:00:46 GMT 2008
Begin forwarded message:
> From: Frank Peters <frank.peters at comcast.net>
> Date: March 14, 2008 9:57:58 PM GMT+02:00
> To: CinePaint Users <cinepaint-users at lists.sourceforge.net>
> Subject: Re: [CinePaint] jpg worse
> Reply-To: CinePaint Users <cinepaint-users at lists.sourceforge.net>
> On Fri, 14 Mar 2008 14:35:59 -0500 (CDT)
> Bob Friesenhahn <bfriesen at simple.dallas.tx.us> wrote:
>> For natural scenes, it is difficult to find visible evidence of
>> JPEG artifacts
>> for reasonable JPEG compression levels. If the image is processed
>> times and saved as JPEG each time, the artifacts will become more
>> That is why saving to JPEG should be the last step.
> JPEG, although useful, is still antiquated technology. JPEG2000
> was supposed to be the new compression standard but for some reason
> it hasn't been widely adopted.
> I have compressed 48 megabyte 16-bit color files down to 2 megabytes
> (and still 16-bit) using JPEG2000 with no discernable loss of quality.
>> The biggest problems noticed with JPEG compression are for non-
>> natural computer
>> renderings with sharp features such as text.
> That's not really a problem. It is only a case that goes beyond
> the JPEG design standard.
> JPEG uses the discrete cosine transform on 8x8 pixel blocks of data.
> The assumption is that there are no sharp transitions within that
> 8x8 block. In the case of line drawings or text, the sharp boundaries
> often end up within the 8x8 block and this represents extremely
> high spatial frequency. During compression, the highest frequnecies
> are discardes leaving a very ugly mess as a result.
> So using JPEG on line drawings or figures, or text, implies that
> the user has made a poor choice of compression algorithms.
> Frank Peters
> This SF.net email is sponsored by: Microsoft
> Defy all challenges. Microsoft(R) Visual Studio 2008.
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