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[Filter Effects][css3-transforms] Using MathML for formulas

From: Dirk Schulze <dschulze@adobe.com>
Date: Fri, 20 Apr 2012 23:48:57 -0700
To: "public-fx@w3.org" <public-fx@w3.org>
Message-ID: <0B15D764-423C-4326-9154-4E7B3E33C466@adobe.com>
Hi FX TF,

I just saw this comment on the Filter Effects 1.0 specification [1] from Erik: "ED: Consider making the following in mathml"

I heard a lot of comments about using MathML instead of text or image alternatives. The Filter Effects specification e.g uses pure text:

<pre>    0  20  40 235 235
  100 120 140 235 235
  200 220 240 235 235
  225 225 255 255 255
  225 225 255 255 255</pre>

<pre>| R' |     | a00 a01 a02 a03 a04 |   | R |
| G' |     | a10 a11 a12 a13 a14 |   | G |
| B' |  =  | a20 a21 a22 a23 a24 | * | B |
| A' |     | a30 a31 a32 a33 a34 |   | A |
| 1  |     |  0   0   0   0   1  |   | 1 |</pre>

or 

<p class="filterformula">Norm(A<sub>x</sub>,A<sub>y</sub>,A<sub>z</sub>) =
   sqrt(A<sub>x</sub>^2+A<sub>y</sub>^2+A<sub>z</sub>^2)</p>

The first two examples are clearly not accessible on screen readers that linearize the content. The second example is a already linearized formula.


In CSS3 Transforms[2] I use a different approach. I included an image of the formula but used TeX formula description to provide some kind of accessibility:

<img alt="\begin{bmatrix} 1 &amp; \tan(\alpha) &amp; 0 &amp; 0 \\ 0 &amp; 1 &amp; 0 &amp; 0 \\ 0 &amp; 0 &amp; 1 &amp; 0 \\ 0 &amp; 0 &amp; 0 &amp; 1 \end{bmatrix}" height="106" src="skewX.png" width="155">


MathML exists for 14 years. Therefore it should be the first choice on web specifications. On the other hand we have still browsers which lack MathML support. Namely MS Internet Explorer and Google Chrome. But even existing implementations in browsers are not consistent [3].

Even if viewers are not consistent, at least specifications should be. Ideally we use MathML and provide some fallback. Sadly I have no idea how it can be done without JS (which is not necessarily enabled and shouldn't be required to read a specification). That is the reason why I choose the image version with alternate text. Any preferences?

Greetings,
Dirk

[1] https://dvcs.w3.org/hg/FXTF/raw-file/tip/filters/index.html
[2] http://dev.w3.org/csswg/css3-transforms/#mathematical-description
[3] http://www.w3.org/Math/testsuite/build/main/overview.html
Received on Saturday, 21 April 2012 06:49:24 GMT

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