[With the dev list]

Hi,

As you can see, Inkscape is storing pies and arcs as Arcs because in fact there are small differences : one is open (arc, you can see this as a line, an open shape) and the other closed (pie, you can see it as a surface). This is an answer for sodipodi:open. The default value must be "false" and this why it's not used for the Pie. Having FALSE or TRUE is a way to know whether it's a pie or an Arc.

About CX and CY : the center of your ellipse (you can see a pie or an arc as a piece of an ellipse...).

About RX and RY : the radius, because this "ellipse" can be regular (a circle) or flatten (an... ellipse !).

Those values are used to render the arc/pie and
for User Interface purposes (to drag and drop control points for exemple).

In plain SVG, you may not have used of those values, so they are not stored and it's simply a Bezier curve whithout knowing it's a pie/an arc.


Romain de Bossoreille
Le 19/07/2012 20:31, mathog a écrit :
I'm back to working on EMF a bit more.  (Need to put libUEMF up on 
sourceforge, as that is what I am using now.
That now works on both big and little endian machines.

Anyway, EMF has Arc, Pie, and Chord types and these are not yet 
implemented for read in inkscape.  For write they
are currently exported as Beziers and not their native types (which is 
probably a good idea.)

I understand the geometry in the EMF file, but corresponding structures 
in Inkscape are a mystery to me.  Created a test figure
containing one quarter of a grey ellipse with a blue boundary all the 
way around ("Pie"), and one quarter of
a red circle ("Arc").  Inkscape did not seem to have any obvious single 
object "Chord".
When saved as plain svg these two objects (in the order listed above) 
are:

     <path
        d="m 172.85715,349.50504 a 75.714287,70 0 0 1 75.71428,69.99999 
l -75.71428,1e-5 z"
        transform="matrix(0.94495594,0,0,2.124136,11.598569,-473.66453)"
        id="path10"
        
style="fill:#7f7f7f;fill-opacity:1;stroke:#0000ff;stroke-width:1.41166961;stroke-miterlimit:5;stroke-dasharray:none;stroke-dashoffset:0" 
/>
     <path
        d="M 288.57143,712.36218 A 68.571426,68.571426 0 0 1 
220,780.93361"
        id="path817"
        
style="fill:none;stroke:#ff0000;stroke-width:10;stroke-miterlimit:5;stroke-opacity:1;stroke-dasharray:none;stroke-dashoffset:0" 
/>

whereas when saved in Inkscape SVG they are

     <path
        sodipodi:type="arc"
        
style="fill:#7f7f7f;stroke:#0000ff;stroke-width:1.41166958;stroke-miterlimit:5;stroke-dasharray:none;stroke-dashoffset:0;fill-opacity:1"
        id="path10"
        sodipodi:cx="172.85715"
        sodipodi:cy="419.50504"
        sodipodi:rx="75.714287"
        sodipodi:ry="70"
        d="m 172.85715,349.50504 a 75.714287,70 0 0 1 75.71428,69.99999 
l -75.71428,1e-5 z"
        sodipodi:start="4.712389"
        sodipodi:end="6.2831853"
        transform="matrix(0.94495594,0,0,2.124136,11.598569,-473.66453)" 
/>
     <path
        sodipodi:type="arc"
        
style="fill:none;fill-opacity:1;stroke:#ff0000;stroke-width:10;stroke-miterlimit:5;stroke-opacity:1;stroke-dasharray:none;stroke-dashoffset:0"
        id="path817"
        sodipodi:cx="220"
        sodipodi:cy="712.36218"
        sodipodi:rx="68.571426"
        sodipodi:ry="68.571426"
        d="M 288.57143,712.36218 A 68.571426,68.571426 0 0 1 
220,780.93361"
        sodipodi:start="0"
        sodipodi:end="1.5707963"
        sodipodi:open="true" />


Start/end are arc positions in radians.
d and transform are SVG objects and I can look up what they mean 
elsewhere.
style I understand.

What are cx,cy and rx,ry?
Why are sodipodi:open="true" amd sodipodi:type="arc" required when 
d="..." is the same in both forms?

Thank you,

David Mathog
mathog@caltech.edu
Manager, Sequence Analysis Facility, Biology Division, Caltech

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