Difference between revisions of "User:Regina/MYDrafts4"

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(Angles in Attribute draw:transform: (checkpoint save))
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Suggestion:
  
Example: The value <tt>scale(0.2 0.5) corresponds to the transformation matrix <math>\begin{bmatrix}0.2& 0&0\\\0&0.5&0 \end{bmatrix}</math>
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Example: The value <tt>scale(0.2 0.5)</tt> corresponds to the transformation matrix <math>\begin{bmatrix}0.2& 0&0\\0&0.5&0 \end{bmatrix}</math>
 
[[File:ScaleX0komma2Y0komma5.png|350px|thumb|left|result of <tt>scale(0.2 0.5)</tt>. Notice that the distance to the origin is scaled too.]]
 
[[File:ScaleX0komma2Y0komma5.png|350px|thumb|left|result of <tt>scale(0.2 0.5)</tt>. Notice that the distance to the origin is scaled too.]]
 
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Example: The value <tt>skewX(25)</tt> corresponds to <tt>matrix( 1 0 tan(25deg) 1 0 0)</tt> with a in degrees.
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Example: The value <tt>skewX(25)</tt> corresponds to the transformation matrix <math>\begin{bmatrix}1& \tan (25deg)&0\\0&1&0 \end{bmatrix}</math>
  
In addition a picture is useful. The term "skew" might be unknown, the term "shear mapping" is more common.
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[[File:SkewX25deg.png|250px|thumb|left|A rectangle transformed with <tt>skewX(25)</tt>. This transformation is also known as "shear mapping".]]
 
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| <tt>skewY(skew-angle)</tt>, specifies a skew transformation by <tt>rotate-angle</tt> degrees along the y-axis.
 
| <tt>skewY(skew-angle)</tt>, specifies a skew transformation by <tt>rotate-angle</tt> degrees along the y-axis.
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Example: The value <tt>skewY(25)</tt> is equivalent to the value <tt>matrix( 1 tan(25 deg) 0 1 0 0)</tt>.
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Example: The value <tt>skewY(15)</tt> corresponds to the transformation matrix <math>\begin{bmatrix}1& \0&0\\\tan(12"deg")&1&0 \end{bmatrix}</math>
  
 
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Revision as of 12:49, 9 August 2012

Problems With Angle Definitions in ODF1.2

Coordinate System

There are two common ways to orientate a Cartesian coordinate system

mathematical orientation
screen orientation

Only when the orientation is determined, terms like "clockwise" are unambigious. Such orientation rule is missing in ODF 1.2.

Suggestion:

If a rule refers to a two-dimensional coordinate system, a Cartesian coordinate system in screen orientation (see figure ##) is used. The directions "clockwise", "counter clockwise", and the edge descriptions "left", "top", "right" and "button" are accordingly defined as shown in figures [##] to [##].

clockwise rotation of the vector (5 2) to vector (2 5)
The rectangle has the "top-left" vertex (1│2) and the "bottom-right" vertex (6│5).

Angles in Attribute draw:transform

These suggestions are all about section 19.228. (Because of the Wiki markup I skipped the characters < and >).

I suggest to give for each single transformation value an example with reference to the corresponding transformation matrix and illustrate that example .

Original Problems and Suggestions
The whole original text is very near to SVG section 7, but a reference is missing.
matrix(a b c d e f), specifies a transformation in the form of a transformation matrix of six values. "The values describe... Typo: The quotation mark before 'The values' has to be removed.
rotate(rotate-angle), specifies a rotation by rotate-angle degrees about the origin of the shapes coordinate system. The orientation of the rotation is missing. I suggest not to use "clockwise" but to define it by an equivalent matrix.

Suggestion:

Example: The value rotate(30) corresponds to the transformation matrix

result of value rotate(30)
scale( sx [ sy ]), specifies a scale operation by sx and sy. It is not clear, that not only the object is scaled.

Suggestion:

Example: The value scale(0.2 0.5) corresponds to the transformation matrix

result of scale(0.2 0.5). Notice that the distance to the origin is scaled too.
skewX(skew-angle), specifies a skew transformation by rotate-angle degrees along the x-axis. Typo: "rotate-angle" should be "skew-angle".

Here is neither clear between which rays the angle is measured, nor what direction is used.

Suggestion:

Example: The value skewX(25) corresponds to the transformation matrix

A rectangle transformed with skewX(25). This transformation is also known as "shear mapping".
skewY(skew-angle), specifies a skew transformation by rotate-angle degrees along the y-axis. Same as skewX. Typo "rotate-angle" and unclear angle.

Suggestion:

Example: The value skewY(15) corresponds to the transformation matrix Failed to parse (lexing error):

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