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[css3-2d-transforms] skew(<angle> [, <angle>])

From: Dr. Olaf Hoffmann <Dr.O.Hoffmann@gmx.de>
Date: Mon, 23 Mar 2009 14:10:07 +0100
To: www-style@w3.org
Message-Id: <200903231410.07664.Dr.O.Hoffmann@gmx.de>
Hello,

this comment applies to the related transformation function in
css3-3d-transforms as well.

http://www.w3.org/TR/2009/WD-css3-2d-transforms-20090320/#transform-functions
http://www.w3.org/TR/2009/WD-css3-3d-transforms-20090320/#transform-functions

I would like to know, which matrix is represented by 
skew(<angle> [, <angle>]).
Currently is is noted a reference to SVG SkewX, what is obviously not
applicable for two angles, respectively there is no difference to SkewX
and the second angle is redundant.

In general skewing or shearing is always related to one direction and
can be represented for example with a matrix 
a b
c d
with:
a+d = 2
ad-bc = 1 (the determinant)

Is it possible to provide a relation between the skewing angle and 
skewing direction and the matrix components and the two angles 
in the definition?
A useful interpretation could be, that the second angle describes the
angle between the x-axis and the skewing direction (0 degree is
the same as SkewX, 90 degree is SkewY and so on), but the
prose does not indicate such a relation. 


Best wishes

Olaf
Received on Monday, 23 March 2009 13:19:02 GMT

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