Hi,
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:
https://bug856375.bugzilla.mozilla.org/attachment.cgi?id=813475
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
