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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?
Here is an article about this issue on LinuxToday.
Nothing's wrong with the patent
At least not for several years until the PNG-format is used all over the internet and apple can make a fortune by taking it out of the drawer.
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?
Je ne parle pas francais.
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.
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. YMMVWhat 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.
Lord Pixel - The cat who walks through walls
A little bigger on the inside than out
If you read the patent, it's an almost textbook example of a painfully obvious 'invention'. The patent clearly admits that the use of a special transparent 'color' in one image is an old technique for blending two images. Next it admits that using a 1-bit alpha mask is a known technique for combining two images. Then it admits that an 8-bit alpha mask has been used to smoothly blend two images in the compositing process! Finally, it admits the 'invention': Let's use a full color image instead of a grayscale image for the alpha mask! Wow! How do they think of these things! What a genius it takes to think that maybe after first using black and white masks, then greyscale, you might try color!
The real clincher is that they go on to list all of these wonderous things you can do with full color mask. But most of their examples only require a good old fasioned greyscale map! Somebody at Apple pulled a fast one at the patent office. The entire 'Fig 1.' shows an example which doesn't even use Apple's 'invention'! It just uses good old fashioned greyscale alpha masks which Apple lists as prior art! Then two of the claims list anti-aliased text! Does anybody do this with color alpha masks? No font renderer spits out multi-color images! They spit out greyscale which is used to merge the text color/pattern with the background! Once again, they claim their invention is needed to do something which everyone does with the prior art method!
On the plus side, it's such a silly invention it's trivial to work around. Here's an idea: use three different alpha masks! One per channel! I wonder if Apple managed to get a patent on that. Hey, here's another nifty idea! Generate the three alpha masks from the three channels of a color image! I bet Apple never thought of that! Only a genius like me could think of that. What an invention! I'll make millions!
Man, this patent is the worst. Check out Claim 3: A method as in claim 1 further comprising displaying the result image. Whoh Nellie! Your going to display the image! Man, that's adds a whole new level of complexity. Usually, I composite images and then just free the memory. But actually displaying an image you've generated! Man, what incredible insight!
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?
I like paying taxes. With them I buy civilization -- Oliver Wendell Holmes
PNG is stealthily gaining acceptance. I think there are three reasons why PNG hasn't gone as far as it should have by now: