PNG Group Unconcerned About Apple's Patent

melquiades writes: "A recent story raised concerns that Apple's patent on some forms of alpha compositing was blocking the development of PNG, MNG and SVG. Not so, says Greg Roelofs, a member of the PNG group: 'The PNG group did discuss the Apple patent several weeks ago, and we decided it was completely irrelevant to PNG itself, almost certainly irrelevant to the pnmtopng utility and to PNGs animated extension, MNG, and probably irrelevant to SVG as well.' Here's the article on OS Opinion. So if it's not a big deal, why was there a general call for prior art to overturn Apple's patent? It looks like some PNG developers got worried, but the core team thinks there's no problem. Is this just a case of the right hand not knowing that the left hand is paranoid?" Once bitten, twice shy?

Comments

Re:PNG's

[Dionysus]

Sites that don't use PNG:
www.salon.com, www.userfriendly.org, yahoo.com, www.redhat.com, www.debian.org, www.gnu.org, and of course, www.slashdot.org.

So, who is using PNG?

An Anti-Software-Patent Database

[Ogerman]

One way that the Open Source community could help fight software patents is to establish a database of prior art. When issues like this come up, relavant prior art would be hyperlinked to the supposed patent.

Re:PNG's

[utoddl]

Just for the record (not that this is scientific or anything) my current ~/.netscape/cache has

• 65 PNGs,
• 1,188 GIFs, and
• 170 JPGs

in it. I suspect that might be a little higher than average in the PNG department because I tend to frequent sites run by rabid free software rebels. YMMV

Re:PNG's

[lordpixel]

What were you compressing? Photographs?

They're not intended to replace JPEG[*] they're best suited for application where you would use a GIF. As with GIF the compression is lossless and best for compressing line art and simple computer generated stuff.

In addition to GIF you also get:

* > 256 colours
* Full 8 bit alpha channel (but not in IE on Windows :(

Then there's MNG - for animated PNGs like animated GIFs and [*] JNG which in a PNG which internally uses uses JPEG compression and thus is pretty good with photos. These are more obscure though. I think JNG might allow transparency/alpha channel, which would be cool, as regular JPEG does not.

Re:As I understand it...

[Doomdark]

I thought so too, after first glance at the patent. However, after reading it through second time, I understood what the patent really is about.

What it is is doing 'compontent-sensitive' image blending. Instead of using single alpha mask or channel for all colour components, it uses a full mask image, that is then used for blending images component by component. When mask image is a gray-scale image, this effectively degenerates to 'normal' alpha blending. However, when using non-gray colours, blending is not linear (as with alpha blending) for the components. In RGB, for example, you could take red value from source, green from destination, and blend blue 50-50 from both, and get... um... probably interesting results?

What I would like to know is if this is useful? What kind of effects can be achieved by using non-grayscale mask images? Potentially it might produce interesting effects... But are those just curiosities?

... and no, obviously this doesn't cause any problems for PNG, which 'only' uses embedded alpha channels.