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Re: Clarification of Parameters to Relative Cubic Bezier Spline / Bug

From: Dean Jackson <dean@w3.org>
Date: Wed, 4 Jun 2003 13:38:34 +1000
To: Andy Bailey <ambailey@usb.edu.co>
Cc: www-svg@w3.org
Message-ID: <20030604033834.GF10057@grorg.org>

Hi Andy,

On Mon, 12 May 2003, Andy Bailey wrote:

> In the specification of  Relative Cubic Bezier Spline (svg 1.1)
> c (x1 y1 x2 y2 x y)+
> it does not what the parameters are relative to ...
> 
> I assumed that the x1 and y1 were relative to the current point
> that x2 and y2 were relative to the final point of the curve (x, y)
> and that x y were relative to the current point.
> 
> This seems to me to be logical

Except that everything else assumes the current point is updated
after the path segment command. Also, other relative points are
offsets from the current point.

It may not be obvious, but it is consistent. Seeing as most
people will be generating paths programmatically, I guess it isn't
so much of a problem (I hope).

> However I am using cocoon with batik to do the rendering and I 
> discovered that the x2 y2 is relative to the
> current point, this doesnt seem to be logical. If one drew the diagram 
> you would draw it as in the diagram cubic01.png in the same page of the 
> svg 1.1 specifications. (that I am attaching)
> 
> Is this a bug in batik or is this the intended form of svg, in either 
> case I think the parameters need to be clarified.

It is the intended form. Maybe we should add something
to 8.3.6 that describes the reference point?

> To everyone involved in svg - thank you for all your hard work.

On behalf of the many people invovled, including the people on this list,
you're welcome.

Dean
Received on Tuesday, 3 June 2003 23:38:40 GMT

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