Re: [Matplotlib-users] removing paths inside polygon

[Andrew D. <da...@at...>]

I tried this and although it sort-of works, it doesn't really do what I
need. I tried using this:

import matplotlib.pyplot as plt
import matplotlib.path as mpath
import numpy as np
import copy

# create figure and axes
fig = plt.figure(figsize=(6, 6))
ax = fig.add_axes([.1, .1, .8, .8])
ax.set_xlim([-3, 3])
ax.set_ylim([-3, 3])

# a circle at the origin with radius 1
circle = plt.Circle((0, 0), 1, transform=ax.transData,
                    edgecolor='k', facecolor='none')

# from Phil's example
exterior = mpath.Path.unit_rectangle()
interior = circle.get_path()
exterior = mpath.Path(copy.deepcopy(exterior.vertices),
                      copy.deepcopy(exterior.codes[:]))
interior.vertices = interior.vertices[::-1]
exterior.vertices *= 6
exterior.vertices -= 3
clip_path = mpath.Path(vertices=np.concatenate([exterior.vertices,
interior.vertices]),
                       codes=np.concatenate([exterior.codes,
interior.codes]))

# lines from the origin dividing the axes into 8 sectors
end_coords = [(3, 0), (3, 3), (0, 3), (-3, 3),
              (-3, 0), (-3, -3), (0, -3), (3, -3)]
for x, y in end_coords:
    line, = ax.plot((x, 0), (y, 0), color='k')
    line.set_clip_path(clip_path, ax.transData)

ax.add_artist(circle)

plt.show()

and the result is the attached image with_clipping.png. You should see that
the circle is no longer circular, and also there are weird line width
issues. What I want it basically exactly like the attached
without_clipping.png but with paths inside the circle removed.

Thanks



On 12 March 2013 16:43, Phil Elson <pel...@gm...> wrote:

> You could just use paths which have holes in them, making the exterior so
> broad that you wouldn't notice the edge of the clipping. I've put together
> an example of doing just that:
>
> import matplotlib.pyplot as plt
> import matplotlib.path as mpath
> import matplotlib.collections as mcol
> import numpy as np
> import copy
>
>
> exterior = mpath.Path.unit_rectangle()
> exterior = mpath.Path(copy.deepcopy(exterior.vertices),
>                       copy.deepcopy(exterior.codes[:]))
> exterior.vertices *= 4
> exterior.vertices -= 2
> interior = mpath.Path.unit_circle()
> interior.vertices = interior.vertices[::-1]
> clip_path = mpath.Path(vertices=np.concatenate([exterior.vertices,
> interior.vertices]),
>                        codes=np.concatenate([exterior.codes,
> interior.codes]))
>
> star = mpath.Path.unit_regular_star(6)
> star.vertices *= 2.6
>
>
> ax = plt.subplot(321)
> col = mcol.PathCollection([clip_path], facecolor='yellow')
> ax.add_collection(col)
> ax.set_title('Clip path')
> ax.set_xlim([-3, 3])
> ax.set_ylim([-3, 3])
>
>
> ax = plt.subplot(322)
> col = mcol.PathCollection([star], facecolor='red')
> ax.add_collection(col)
> ax.set_title('Target polygon')
> ax.set_xlim([-3, 3])
> ax.set_ylim([-3, 3])
>
>
> ax = plt.subplot2grid((3, 2), (1, 0), colspan=2, rowspan=2)
> col = mcol.PathCollection([star])
> col.set_clip_path(clip_path, ax.transData)
> ax.add_collection(col)
>
> ax.set_title('Target polygon clipped by clip_path')
> ax.set_xlim([-3, 3])
> ax.set_ylim([-3, 3])
>
> plt.tight_layout()
>
> plt.show()
>
> [image: Inline images 1]
>
>
>
> There are other options if this doesn't cut the mustard.
>
> HTH,
>
>
>
>
>
>
>
> On 12 March 2013 15:37, Andrew Dawson <da...@at...> wrote:
>
>> Hi
>>
>> I'd like to be able to clip a line so that the portion of it lying
>> outside of a given polygon remains visible and the part that lies inside of
>> the polygon is not visible. What I want is basically the opposite of:
>>
>>     line.set_clip_path(polygon)
>>
>> which leaves only the part of the line inside the polygon visible. Is
>> this possible?
>>
>> I know I can just fill the polygon with the background color or something
>> but this gets messy when there are other lines on the plot that don't need
>> to be clipped.
>>
>> Thanks,
>> Andrew
>>
>>
>> ------------------------------------------------------------------------------
>> Symantec Endpoint Protection 12 positioned as A LEADER in The Forrester
>> Wave(TM): Endpoint Security, Q1 2013 and "remains a good choice" in the
>> endpoint security space. For insight on selecting the right partner to
>> tackle endpoint security challenges, access the full report.
>> http://p.sf.net/sfu/symantec-dev2dev
>> _______________________________________________
>> Matplotlib-users mailing list
>> Mat...@li...
>> https://lists.sourceforge.net/lists/listinfo/matplotlib-users
>>
>>
>


-- 
Dr Andrew Dawson
Atmospheric, Oceanic & Planetary Physics
Clarendon Laboratory
Parks Road
Oxford OX1 3PU, UK
Tel: +44 (0)1865 282438
Email: da...@at...
Web Site: http://www2.physics.ox.ac.uk/contacts/people/dawson