Font smoothing in Pages: It’s about text transparency

Posted by Pierre Igot in: Anti-Aliasing Hall of Shame, Pages
February 9th, 2006 • 10:18 am

I have written about font smoothing in Pages on a couple of occasions. In a nutshell, the problem is that, regardless of the font smoothing option that you’ve chosen in the “Appearance” preference pane in System Preferences, Pages uses standard “best for CRT” font smoothing.

Standard font smoothing does not use subpixel anti-aliasing (it only uses shades of grey, not coloured pixels) and, for most people, this type of font smoothing looks “skinny” and excessively blurry on a flat-panel display. Hence the other font smoothing options provided by Apple in System Preferences, including the “Medium – best for Flat Panel” option.

Both versions of Pages (1 and 2) fail to honour the user’s preference as selected in the “Appearance” preference pane. Regardless of the user’s preferences, Pages uses standard anti-aliasing with pixels only in shades of grey.

Other people have recently chimed in on the issue.

John Gruber says that I think it’s due to Apple’s “incompetence,” even though I never used that word myself in my posts on the subject. I did say that it was quite “unbelievable” that the problem was still not fixed, and I did speculate on the reasons for this. But like I said in a comment on Michael Tsai’s blog item on this topic, Apple’s apparent “refusal to fix [the problem] leaves the door open to speculation about its reasons/motives.

In any case, people who know more about the technology used for font smoothing than I do have provided more clues about the root of the problem. In particular, Michel Fortin states that it is “simply impossible to draw subpixel anti-aliasing on a transparent background” (his emphasis).

Since Pages is also a page layout tool and has to support transparency, it appears that this is the reason for Pages’s lack of support for other font smoothing styles. In other words, it appears that Apple engineers have decided that the lack of support for subpixel anti-aliasing in Pages is an acceptable trade-off.

The trouble with this is that it is not entirely convincing. First of all, Apple has made no attempt to communicate with Pages users on this subject and justify its decision. The lack of support for other font smoothing styles is not mentioned anywhere in the Pages documentation or on Apple’s web site, as far as I know. And the bug reports I have submitted on this issue have remained unanswered too.

This is not a small issue that will just go away by itself. Font smoothing is an essential dimension of the visual experience in Mac OS X, and the lack of support for subpixel anti-aliasing in Pages causes a significant amount of undesirable eye strain for Mac users with flat-panel displays. Given that Pages is not just a page layout application, but also a word processor, this is a rather fundamental issue.

Then there is the troubling fact that this is not an isolated incident, and that Apple also fails to honour the user’s font smoothing style preferences in other parts of Mac OS X, most notably in the right-hand side of the menu bar. What’s the excuse for not supporting subpixel anti-aliasing in menu extras, when subpixel anti-aliasing is fully supported in menu items on the left-hand side of the menu bar?

Finally, there is the fact that Pages’s main competitor and runaway leader of the word processor market, Microsoft Word, does support subpixel anti-aliasing and does honour the user’s font smoothing style preference as defined in the “Appearance” preference pane in System Preferences.

It should be noted that Microsoft Word also comes with its own set of page layout tools. They might be poor compared to Pages’s feature set, but they do exist, and, out of curiosity, I tried to see what would happen when drawing a block of colour behind some text in a word document. Here’s the result of my experiment:

Text over background in Word

I did this by simply typing some text and then drawing a rectangle with a solid colour background and moving the rectangle behind the text.

If you zoom in on the text, here’s what you see:

Text over background in Word - zoomed in

It still looks like subpixel anti-aliasing to me!

Now, I understand that the issue here is essentially the transparency of the text iself, not the transparency of the text’s background. Word does not support text transparency (as far as I know), whereas Pages does. (If you have a block of text in Pages, you can change its “opacity” to less than 100% in the Inspector window.)

But how often will the average Pages user use text transparency—compared to the frequency of situations where he’ll be typing and reading text with 100% opacity? Surely in light of this Apple could have come up with a scheme that fully supports subpixel anti-aliasing when the opacity is 100% and then switches to standard anti-aliasing when the opacity is less than 100%!

Once again it looks like Apple has chosen to favour theoretically “cool” features such as text transparency over interface consistency and user comfort in everyday computing activities. Which is more important?

So the bottom line for me as an end user is clear: Word respects the user’s font smoothing style preference, and Pages does not. Whether there are highly technical reasons for this is ultimately of little interest to me. It’s about eye strain and visual comfort, not about Quartz compositing and off-screen rendering. My eyes’ comfort is more important to me than some hypothetical advantage with text transparency that I never use.

(Note: Apple’s own style guide spells anti-aliasing with a hyphen. So that’s the spelling I am using here. The style guide doesn’t specify whether it should be subpixel or sub-pixel, though.)

4 Responses to “Font smoothing in Pages: It’s about text transparency”

  1. ssp says:

    Hm hm hm.

    Perhaps I’m misunderstanding things… but Apple’s very own Safari doesn’t seem to have problems with sub-pixel anti-aliased transparent text.


  2. Pierre Igot says:

    Now that is very interesting. So it does indeed look like Mac OS X is able to do subpixel anti-aliasing and text transparency over coloured backgrounds at the same time.

    Which brings us back to the question of why Pages does not support it. I wonder what Michel Fortin thinks about that.

  3. Pierre Igot says:

    Michel Fortin has now posted a clarification in the comments on his post. I guess what it boils down to is still the issue of whether whatever advantages transparency support brings are worth sacrificing text readability for LCD flat panel users. My view is clearly that they are not.

  4. Tom Gidden : Image resampling for LCD screens says:

    […] My browser of choice, Camino, has a small bug whereby the font smoother sometimes switches back to greyscale mode. The worst part is that it doesn’t always happen across the whole window, but when a rectangle is redrawn (eg. while scrolling). I think it mainly occurs when there’s DHTML magic going on, and I suspect I know why: when the text is part of a layer that may be composited on top of other content, the RGB font smoother is not really able to be used, unless the entire layer stack is prebuffered. This is due to the lack of sensible subpixel transparency when compositing. [Update: Pierre Igot describes a similar problem with Apple’s Pages, and Michael Fortin explains why, and it turns out I was probably right.] […]

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