Windows 8 Font Issues?

[John Hudson]

This is what I'm not quite getting. Isn't that true of all anti-aliasing?

No, because in previous antialiasing glyphs have been positioned on full pixel widths, i.e. the 0,0 coordinate of each glyph's advance width has always been positioned on the leading edge of a pixel. This was also true of ClearType subpixel rendering in the GDI implementation. This accounts for sometimes uneven spacing in traditional greyscale and GDI ClearType.

In DirectWrite ClearType and Metro greyscale antialiasing, fractional sub-pixel positioning is used, i.e. the 0,0 coordinate of a glyph may occur anywhere within the pixel. What is means is that spacing is much more even, but that there is variation in the actual pixel pattern for the same glyph at different places in a line of text. In the Metro greyscale rendering, this variation displays as differences in the grey tint of pixels (in DWrite CT it displays as differences in the colour tinting, and is generally more prevelant and noticeable than in the Metro greyscale). This is why I classify the Metro greyscale antialiasing as 'sub-pixel', because the pixel tint is being affected by the position of the glyph according to fractional positioning.

[John Hudson]

Here's a pretty good illustration:

On the left is the Metro greyscale antialiasing (this screen capture was from the public beta of Win8; I don't know if the rendering was further tweaked for the release version); on the right is the same text string in GDI ClearType antialiasing. Zoom in to see the use of grey only in the Metro rendering and colour in the GDI CT. Note that stem weights are more consistent in the GDI CT rendering, but spacing is more consistent in the Metro rendering. Note particularly the above-line clash of the reph mark and following ikar in the GDI CT rendering, which has resulted from the full-pixel positioning bringing the latter too close; this is much better with the Metro fractional positioning (but would be better still with DWrite CT, which would have better stem weight consistency).

[aluminum]

"Metro greyscale antialiasing"

Ah! That makes sense, as antialiasing uses the entire pixel, it can truly be grayscale (or in this example, matched to the type color).

It gets confusing when when the term 'sub-pixel' and grayscale are used together...but the term 'fractional positioning' helps clear that up (my understanding is that Metro uses full-pixel anti-aliasing but allows the glyph borders to land in the middle (or some fraction thereof) a pixel).

[aluminum]

and that's likely a natural path to take. Sub-pixel font smoothing has a limited remaining shelf life given mobile (rotatable) screens and high-ppi screens. The Win8 method would seem to be applicable for those uses.

[Bendy]

Thank you for your patient explanation, John, I see the distinction. I presume one implication of the Metro sub-pixel positioning (and the DWrite CT) is that x-hinting instructions are ignored, since they're trying to align the stems to whole pixels so that glyphs have a consistent appearance when rasterised? Or do I need to learn more about hinting before that starts to make sense?

>In the context of Metro rendering, asymmetric refers to the difference in x- and y-direction supersampling (at text sizes). The rendering is 8x4 greyscale, meaning that the x-direction antialiasing has double the senstitivity of the y-direction antialiasing.

What's supersampling? I'm guessing it's the way the rasteriser is looking at glyph outlines and deciding how much black to put into each pixel. If that's right, then it seems that 8x4 greyscale means that each pixel is assessed by breaking it down and looking at how many of the 32 virtual sub pixels the outline covers, which results in the pixel being attributed one of 32 different levels of grey.

[hrant]

It's just a damn shame it looks worse than GDI. :-/

Why sacrifice the quality just because you can rotate a screen? So what if text looks slightly different depending on how you're holding a device?

hhp

[John Hudson]

What's supersampling?

Think of a glyph outline being stretched to a larger number of pixels than actually requested for the target display size/resolution, and then the mapping of the outline to those pixels being downsampled (like a scaled down JPEG) relative to the requested size. So in the case of an 8x4 asymmetric supersampling, each pixel in the requested ppem size is first represented by 8 horizontal pixels and 4 vertical pixels, and then scaled down to the requested size. Obviously at larger sizes more refinement of the relationship of outline to pixels is possible and hence more antialiasing precision (samples) is available. This captured information influences the rendering at the target size, where the relationships that were relative to pixel dimensions in the supersampling become relative to sub-pixel dimensions in the final rendering.

[John Hudson]

Rotating screens may be a factor, but I believe the issue for Win8 was lack of time to optimise the ClearType code to reduce performance hits in the heavily animated Metro UI. Simply put, the greyscale rendering is faster. If the ClearType code can be optimised to make it render quickly enough to meet the Metro developers' requirements, I hope it will be reinstated for Win9. The stroke density is much better.

[aluminum]

Performance certainly may have been a priority.

But it also seems like Microsoft really wants Win8 to succeed on the tablet. I think both the screen rotation and higher PPI of that screen would justify this method (IMHO).

"Why sacrifice the quality just because you can rotate a screen?"

Well, one argument would be consistency. Having type look better in one rotation than the other might not be the best user experience. (But I'm not even sure if that's really all that important anyways, as I *think* most of the handheld Win8 devices are using high PPI screens, so sub-pixel rendering is likely moot).

[JamesM]

> But it also seems like Microsoft really wants Win8 to succeed on the tablet.

Yep, tablet sales are growing rapidly while PC sales are stagnating. Many analysts are predicting that tablet sales will exceed laptop sales within a few years.

[John Hudson]

I really don't think the whole rotation question played a role in the switch to the Windows 8 greyscale rendering. Remember, the alternative -- already implemented through most of the development cycle -- was DWrite ClearType, so there was already bidrectional antialiasing (unlike GDI). If tablet and phone rotation had been a concern for text rendering, I would expect this to have been something addressed quite early in the new operating system development cycle. The Metro greyscale rendering was implemented at the last minute, after initial beta versions of Win8 had shipped with ClearType, in response to performance complaints.

[dberlowgone]

Did you specify grey, or is it time to change the ribbon? "On the left..." is both specified and set in black type, off windows. :)

[John Hudson]

Yes, the illustration text -- taken from a website viewed in different versions of IE with different renderings -- was spec'd grey. For illustrating the differences between the rendering models, it could have been pink, orange, purple or, indeed, black. It just happened that the example I had to hand was grey, but I should have mentioned that in case anyone thought it was intended to be black.

[hrant]

I might have been suspicious too but recently saw another comparison (in black) and concluded that GDI was better.

hhp

[dberlowgone]

This one too? (from your link above).

[dberlowgone]

"For illustrating the differences between the rendering models, it could have been pink, orange, purple or, indeed, black"

Really. I think, when comparing rendering or any kind, but especially one that involves color subpixelation vs one that doesn't, an appropriate comparison cannot be done without black.

[hrant]

David, what are you getting at?

hhp

[John Hudson]

David, if the purpose is to compare for particular purpose, I fully agree, especially if that purpose is reading text. I just wanted to illustrate different characteristics of the two rendering systems, for which purpose I considered the screenshot that I had on hand to be sufficient: you can see the difference in spacing and the difference in stroke weight regularity and density.

[Renaissance Man]

"If I upgrade to Windows 8, ..."

Don't upgrade. Buy a new computer. Read the following:

Walter Mossberg (WSJ) on upgrading: www.j.mp/w8noup

Thomas De Maesschalck: Two months with Windows 8 www.j.mp/win666

[hrant]

Thanks for the tips. Actually I was never planning on upgrading my Rex; the plan is to get a new machine. And I've decided to go for Win7 Ultimate with XP support.

hhp

[Renaissance Man]

Win7 the New XP SP3?
If you’re still running Windows XP, take the time to review your options. Microsoft ends support for XP in 15 months, on April 14, 2014—the last official day the OS will get security updates. With the verdict still out on Windows 8, now might be a good time to give yourself the present of a new Windows 7 machine. Think of Win7 as the “new XP SP3.” It might be the next long-lasting, long-supported Windows operating system that Microsoft will need to pry our fingers from.
—Susan Bradley, WindowsSecrets.com, Dec. 6, 2012

[Richard Fink]

Sorry for my tardy return....

hrant: For font production, I think you made the right decision. And yes, I just migrated my entire setup from WinXP to XP running in XP Mode. I suppose if I had really had the time to spend, I could have gotten everything going OK in Win7 64 bit, but what for? A waste of time. Everything I use was built during the XP era. I don't have the patience for tweaking a Windows configuration anymore. Sucker broke my command line scripts and that was it - back to XP in XP Mode.

5star: I run my Latitude and ANY laptop I own on a cooling pad so I'm not sure if it's getting too hot or not.
As for running 32 bit apps - see my response to hrant above.

BTW - Nice to see MSFT finally enter the tablet/touchscreen fray after watching, watching, watching endlessly it seemed. But "creative imitation" has always been their strategy and it requires watching the other players for awhile before entering the market.

I think it will work yet again and we'll see a major rebound. And I like how they took their myopic fixation with developing a stylus-on-screen interface and found a way to turn it into a plus.

[Richard Fink]

@Renaissance Man:

I don't believe MSFT will discontinue security updates by that date -April 14, 2014.
That might be what they are announcing but I'll believe it when I see it.

And...... since I'm not running Office apps or anything sensitive within the XP Virtual Machine, I really don't care if they freeze security support or not.

[oldnick]

Richard,

“Creative imitation” may be a misnomer in this case. From what I can gather, Windows 8 Metro interface is considered to be the wave of the future—less is more, if you will. The whole Apple thrust—higher res, more glitz—turns the interface into a bandwidth hog, which is great for the IPSs, but it totally lousy for the people who have to pay for that bandwidth. If I were a person given to conspiracy theories (which, I am, but I don't want to advertise it), I would aver that Apple's ultra-high-res approach to tabs/mobile/etc. has been developed in cahoots with carriers to ensure that that maximum amount of data transfer occurs (billable units) at any time. Win 7 Pro 64-bit rules. Totally. Indubitably. My story and I’m sticking to it…

[JamesM]

> Windows 8 Metro interface is considered to be the wave of the future

Maybe, but Win 8 PCs and tablets are selling poorly so far. Google for numerous news articles about disappointing sales.