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Clarification of Path Data

From: Bernhard Herzog <herzog@online.de>
Date: 18 Aug 1999 11:59:33 +0200
To: www-svg@w3.org
Message-ID: <m3btc5pfy2.fsf@greebo.nodomain.de>

I've recently begun to implement SVG import/export filters for my
drawing program Sketch, and I think the current draft is a little
unclear about some aspects of the path data.

For example, what are relative coordinates relative to? I assume they're
relative to the current point, but that's never stated explicitly,
AFAICT. An alternative interpretation of relative coordinates would be
that each coordinate pair is relative to the preceding one. This would
make a huge difference for e.g. the curveto command.

If relative coordinates are relative to the current point, it seems to
me that these two statements are contradictory:

a) from section 10.3.1: "The command letter can be eliminated on
   subsequent commands if the same command is used multiple times in a

b) from section 10.3.4 (lineto command): "At the end of the command, the
   new current point is set to the final set of coordinates provided."

I think a) implies that the command letters can be dropped without
changing the meaning. If this is the case, then in an 'l' command
(relative linto) with more than one coordinate pair, each pair is
relative to the preceding one. b) on the other hand means that the
coordinates are relative to the last point before the 'l' because that's
the last time the current point changed. Which interpretation is right?


Bernhard Herzog	  | Sketch, a drawing program for Unix
herzog@online.de  | http://www.online.de/home/sketch/
Received on Wednesday, 18 August 1999 05:57:51 UTC

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