Hi.

Trying to learn Inkscape + Python scripting for Inkscape.

Have made a python program to make tangents between two circles.
So far I have got the routine to add the lines to a SVG file containing nothing but the two circles (arcs).

How do I get data from two selected circles (drawn by inkscape as arcs?!) to my python routine?
Any leads would be appreciated.

RGDS Ragnar

Hello
I don't want to mislead you, but:
- Do the following: Open inkscape and create a circle, or a ellipse, or an arc
- You press Shift+ Ctrl + X And you open the XML editor
- Now you observe that in fact the arc, or ellipse or circle is ... a path!!
--- So, it seems to me that is not an arc as you say, but a path

- Also you observe this attribs :
--- sodipodi:cx
--- sodipodi:cy
--- sodipodi:rx
--- sodipodi:ry
--- sodipody:type = arc

To get that last attributes you can use the python library lxml.

BEWARE:
[To put the things in a simple way in SVG (or XML), an ELEMENT is separated between "<" and "/>". Using the lxml lib you get the attribs of an ELEMENT as ELEMENT.get(key, default=None), where "key" is the name of the attribute,etc. ]

But we aware that if you, in inkscape move , or scale or rotate the circles/paths, you are doing a transformation. Inkscape saves this transformation as other attribute that may or may not appear in your circle/path element.

Mmm, right now i don't know what else to say . Hope you can resolve the problem

Hi.

Thanks, the XML editor is kind of neat, I can cut & paste the values for the circles to&from my python program.
I can also "read" the positions and radii for the circles from the SVG file and add the lines for the tangents without problem, but how do I "read" the values from two selected circles in a script? (in case there are more circles in the SVG file). Will have to study the scripts already in Inkscape a little closer in order to try to get an understanding of what's going on. I am also still a little bit confused by the use of a path to draw a circle - tagged as an arc!

Thanks again.
RGDS Ragnar

Hi,

Well , I don't know if I can explain better.
mmm ... look at the wiki of inkscape:

http://wiki.inkscape.org/wiki/index.php ... Extensions

You also have to learn something about parsing an XML document in python,
I 've used this sources of information:

http://lxml.de/tutorial.html
http://infohost.nmt.edu/tcc/help/pubs/p ... index.html

And I repeat:
[.... Using the lxml lib you get the attribs of an ELEMENT as ELEMENT.get(key, default=None), where "key" is the name of the attribute,etc. ]

And yes, you are right there: look how are implemented other extensions.

It also helps show your code.

- Yes it's complicated how inkscape manage drawing circles. I believe it's to emmm "facilitate"(?), drawing circles, ellipses and arcs.

- Other thing. the next inkscape version is implementating a tangent snapping to circles. but i don't know much about that

Greetings