Cleartype In Depth

spectecjr writes "Looks like Microsoft have at last released some detailed information on their ClearType technology. It involves a whole load of Fourier Analysis to come up with the optimal distribution of color energy and to reduce color fringing. You can read the paper and more indepth info in PDF and gZipped PostScript, as well as the paper submitted to the IEEE Signal Processing Letters journal PDF. Samples of ClearType vs. standard anti-aliasing are up online too."

Comments

Yick, hurts my eyes.

[Juggle]

All arguments over wether this is actually different than what Apple did way back with the II or not aside I'm not as impressed as I had expected to be.

Back when this was first announced I thought it made sense and would work great. I even read a few pages which showed how Apple did the same thing and loaded the samples on there up on a few screens to see how they looked. Yeah there was a difference but nothing major.

Now this comes across with what sounds like samples made using the exact algos that MS is touting as their great new innovation. So I pull out the old palmtop and laptop and check the page out.

But this looks like hell to me! I can see major color fringing and in those text waterfall examples I see rainbows in the CT examples that are so prominent they make it harder for me to read than the AA example! Yuck!

Does anyone else notice it as much as I do? Or are my eyes just abnormally color sensitive?

Anti-aliasing on conventional monitors.

[tjwhaynes]

Cleartype is basically antialiasing which takes note of the way in which the LCD screens make up their pixels. From the comparative samples, it's difficult to compare the two samples given on a normal (i.e. CRT) monitor. I strongly suspect that this is not going to make such an impact on CRT-based techniques for several reasons. The conventional monitor scans a modulated electron beam across a mask before hitting the coloured phosphors which make up the display. Despite the regular display patterns of the mask, a pixel on a conventional CRT could line up with any combination of the coloured phosphors, as the start of each pixel could be on any of red/green or blue phosphors. The Cleartype technology relies on being able to make use of the arrangement of single-coloured pixels to enhance the imagery (and yes, I do believe it can make a difference) and must therefore be aware of the mapping from the resolution of the image on screen to the resolution of the actual screen matrix itself.

Something does strike me as odd in the samples though. One of the things that ideal anti-aliasing should do is give a completely even weight to every letter/symbol in a font (assuming that the base font definition is designed with this in mind). However, scrutiny of the samples seems to suggest that either the font they are using is subtly broken in this respect, or that the anti-aliasing and Cleartype render used here is not ideal - take a look at the weighting of the 'x' character, and slightly less of a problem is the 'k'. This could be hinting gone wrong, or a bad font definition - I'd be interested to know whether it looks better on an LCD screen.

Cheers,

Toby Haynes

Microsoft Research

[drivers]

This is an interesting side of Microsoft I hadn't realized existed: Microsoft Research. It looks like they are working on a lot of very interesting stuff. I was searching through their stuff I found that one of the things they were working with was IPv6 related networking, and you can download a web server called "Fnord!". I downloaded it, and checked out license.txt and it is the GPL! Apparently they used Fnord! written by someone else and used it as a basis for some research software, and you can download it, source and everything. Cool.

The relevant freeware

[konstant]

Here is the software of the guy who claims Apple figure all this out years ago. He has a demo written (idiosyncratically enough) in pure i386 assembly:

Free and Clear

However, his discussion doesn't seem nearly as complex as the one we have linked in this article. My feeling is that the idea of sub-pixel manipulation is one of those "floating revelations" that recur to more than one clever mind, but that MS Cleartype is the first practical application.

Oh, and here's the cleartype site at MS. Be sure to view it with an LCD screen - otherwise you won't get the benefit due to the triangular distribution of color spots on a CRT:
MS Reader

-konstant
Yes! We are all individuals! I'm not!

IBM Research Scientist's Comments on ClearType

[QBasic_Dude]

Former research IBM scientist Ron Feigenblatt has some interesting comments about Microsoft ClearType. Feigenblatt explains subpixel addressing, dynamic pixels, and color convergence problems on LCDs.

Another Microsoft "Innovation"

[GSearle]

This is another example of Microsoft taking someone else's idea, calling it their own innovation, and making a big fuss over it. Really this guy has been pushing this technology for quite a while before Microsoft picked it up.

The Apple II doesn't really do this. It uses the properties of the NTSC colorburst signal to create color from a synchronized high-resolution monochrome signal. The physical "subpixels" on the CRT can't be aligned to this signal, and the end result is fuzziness, not clarity. The R,G,B phosphors on the screen are not directly addressed.

CRT's and even analog LCD's don't gain anything from this, as this technology needs direct access to the R,G,B elements of the display to create antialiased text that is as sharp as possible. It even needs to know the order of the RGB elements. This done through wholly digital displays that directly address the color pixels on the display, such as an LCD on a laptop. The next step would be to make this independent of the display type, with tuning tools or profiles for individual display devices.

Television does this naturally, being a wholly analog system. Point a color camera at some text, and the edges of the text will fall on the color elements within the camera, irregardless of arbitrary pixel boundaries. If you magnify a still image on a TV set, you'll notice that any sharp edges are defined independantly of the positions of the color elements, and they are "smooth". In contrast, any computer-generated edges show a bias toward pixels, causing some jagginess in even the best anti-aliased graphic. Of course, if the source camera and the receiving TV set have different color element geometries, the result will be a little off.

Whatever you call it, this is antialiasing taken to the max. I'm glad that someone is taking it seriously, even if it's Microsoft. CG for television should take notice, too, to try to simulate the natural look of purely analog signals.