[REQ] better default JPG compression

[Zom-B]

Hey guys...

I just noticed how awefull the default JPG compression of Indigo saved JPGs is!
Here a 4x zoomed example of Material ID tracer. could you guys lower the compression to a amount
that preserves overall quality better?!

[dcm]

Thanks Arty

[galinette]

I can see a little bit of DCT compression, but what I see even more is the 4:2:0 chroma subsampling which is not a tunable feature of jpeg. On normal pictures you barely see it but on hard edges of saturated colors you see it a lot.

Solution : save as PNG...

But it's true, a quality slider would be nice

Etienne

[Zom-B]

Yes, such a flat colored example is not the best category to demonstrate the "strength" of JPG compression
Anyway, my point here is that after trying a little in PS I found out, that I get same JPG artifacts by saving in PS in quality of 6 of 12 in baseline mode... thats 50% of possible quality.

Rendering unbiased and then (being able to) saving so ultra biased should be forbidden

I use PNG to 99% of my time, but that saving JPG exists and should be tweak-able quite easy for a better result!

[galinette]

Yes, I just made the photoshop test, it seems that chroma subsampling is only done below 6, my mistake

That's maybe the jpeg library used by Indigo which is in cause (Qt?)


Edit : found some explanation here : http://www.impulseadventure.com/photo/c ... pling.html

Etienne

[lycium]

+100 for this from my side, I absolutely hate JPEG compression artifacts.

The problem is that very few libraries (and consequently programs) offer the ability to turn off chroma subsampling. I make my JPEGs in exactly one way, using IrfanView: https://dl.dropbox.com/u/3038174/img/ho ... images.png

It would be good if Indigo's JPEG saving could do this automatically though, worth looking into

[galinette]

Libjpeg! Should be OK regarding license (only an acknowledgement is required)

From my side, I only use PNG. It's a pity to add compression to rendered images!

Etienne

[lycium]

+100 for this from my side, I absolutely hate JPEG compression artifacts. On the other hand, JPEG is worthwhile for final image display if it's done well.

The problem is that very few libraries (and consequently programs) offer the ability to turn off chroma subsampling. I make my JPEGs in exactly one way, using IrfanView: https://dl.dropbox.com/u/3038174/img/ho ... images.png

It would be good if Indigo's JPEG saving could do this automatically though, worth looking into

[OnoSendai]

We use LibJPG for core jpeg saving (auto saving of images, save on halt).
For saves done through the GUI, we let Qt do the JPEG writing.

[lycium]

Incidentally, I've noticed a recent bug with Chrome which I think stems from its new GPU rendering codepath: if you look at high contrast edges in a JPEG image, Chrome has not-so-subtle blocking artifacts whereas for example Internet Explorer doesn't.

So when comparing JPEG quality, you can't use Chrome as a reference! (right now)

I really should report this because it seems like essentially no one else notices...