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Re: JPEG 2000 (was: Multiple image files?)

From: Frédéric Kayser <f.kayser@free.fr>
Date: Wed, 15 Jan 2014 01:27:58 +0100
Cc: Eric Portis <lists@ericportis.com>
Message-Id: <D73D1B3A-A05E-4C48-B77E-0EFF833F0382@free.fr>
To: public-respimg@w3.org
Setting quality to 50 in Photoshop activated 4:2:0 chroma sub-sampling, but you didn't use sub-sampling for the JPEG2000 file (-s 2,2).

To visually see the effects of chroma-subsampling this test pattern can be used:
Notice the impact on color when quality is set to 50 and below compared to 51 and more.

Eric Portis wrote:

> On Tuesday, October 22, 2013 at 12:38 AM, Yoav Weiss wrote:
>> I think it would be extremely helpful if someone could run some JP2K tests and prove or disprove Henri's claims.
>> The following comment https://groups.google.com/d/msg/mozilla.dev.platform/9NKc7OeEFLM/kH35YH62uMUJ suggests that it's a matter of encoder settings.
> It took a few months, but I finally got around to running some tests:
> http://ericportis.com/posts/2014/resolution-progressive-jpeg2000-performance/
> The results for JPEG2000 were not good.
> See the encoder settings used in footnote #3. From my reading of the docs, the key one seems to be setting RLCP progression order, vs the default LRCP (which is progressive quality, ala Progressive JPEGs).
> —eric

(image/png attachment: quality50vs51.png)

Received on Wednesday, 15 January 2014 00:28:30 UTC

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