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How to plot a polygon with distinct colors for border and interior ?

asked 2014-10-23 10:37:12 -0500

FrédéricC gravatar image

updated 2015-01-13 13:38:39 -0500

I would like to have a green polygon with black border. I can achieve this by superposing two polygons:

sage: polygon([[0,0],[0,1],[2,1],[1,0]],color='limegreen',fill=True)+polygon([[0,0],[0,1],[2,1],[1,0]],color='black',fill=False)

Is it possible to do that with one polygon ?

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Comments

This is now http://trac.sagemath.org/ticket/17209. Needs review.

FrédéricC gravatar imageFrédéricC ( 2014-10-24 02:42:36 -0500 )edit

2 answers

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answered 2014-10-23 14:41:49 -0500

kcrisman gravatar image

Matplotlib polygons do have edgecolor as a keyword. Currently the way Sage wraps these you might have to do a little work to get that to work out right. In principle the following should work, but it doesn't seem to:

sage: P = polygon([[0,0],[0,1],[2,1],[1,0]],color='limegreen', thickness=2)
sage: p = P.matplotlib()
sage: p.set_edgecolor('black')
sage: from matplotlib.backends.backend_agg import FigureCanvasAgg
sage: p.set_canvas(FigureCanvasAgg(p))
sage: p.savefig('test.png')

as can be seen by trying

sage: !open test.png

Matplotlib has added a lot of functionality we haven't wrapped properly yet.

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answered 2014-10-23 13:06:29 -0500

ndomes gravatar image

You can use your own python function:

def rim_polygon(V,border_color='black',**kwargs):
    G = polygon(V,**kwargs)
    d = kwargs.get('thickness',1)
    G += polygon(V,color=border_color,fill=False,thickness=d)
    return G

L = [(0,0),(0,1),(2,1),(1,0)]
rim_polygon(L,color='red',alpha=0.5,thickness=4,axes=False)
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Well, this is essentially still a sum of two polygons..

FrédéricC gravatar imageFrédéricC ( 2014-10-23 13:28:26 -0500 )edit

Indeed, but a polygon with distinct border is a sum of two graphic objects.

ndomes gravatar imagendomes ( 2014-10-23 17:45:40 -0500 )edit

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Asked: 2014-10-23 10:37:12 -0500

Seen: 1,027 times

Last updated: Oct 23 '14