importnumpyasnpfrommatplotlib.artistimportArtistfrommatplotlib.linesimportLine2Ddefdist_point_to_segment(p,s0,s1):"""    Get the distance from the point *p* to the segment (*s0*, *s1*), where    *p*, *s0*, *s1* are ``[x, y]`` arrays.    """s01=s1-s0s0p=p-s0if(s01==0).all():returnnp.hypot(*s0p)# Project onto segment, without going past segment ends.p1=s0+np.clip((s0p@s01)/(s01@s01),0,1)*s01returnnp.hypot(*(p-p1))classPolygonInteractor:"""    A polygon editor.    Key-bindings      't' toggle vertex markers on and off.  When vertex markers are on,          you can move them, delete them      'd' delete the vertex under point      'i' insert a vertex at point.  You must be within epsilon of the          line connecting two existing vertices    """showverts=Trueepsilon=5# max pixel distance to count as a vertex hitdef__init__(self,ax,poly):ifpoly.figureisNone:raiseRuntimeError('You must first add the polygon to a figure ''or canvas before defining the interactor')self.ax=axcanvas=poly.figure.canvasself.poly=polyx,y=zip(*self.poly.xy)self.line=Line2D(x,y,marker='o',markerfacecolor='r',animated=True)self.ax.add_line(self.line)self.cid=self.poly.add_callback(self.poly_changed)self._ind=None# the active vertcanvas.mpl_connect('draw_event',self.on_draw)canvas.mpl_connect('button_press_event',self.on_button_press)canvas.mpl_connect('key_press_event',self.on_key_press)canvas.mpl_connect('button_release_event',self.on_button_release)canvas.mpl_connect('motion_notify_event',self.on_mouse_move)self.canvas=canvasdefon_draw(self,event):self.background=self.canvas.copy_from_bbox(self.ax.bbox)self.ax.draw_artist(self.poly)self.ax.draw_artist(self.line)# do not need to blit here, this will fire before the screen is# updateddefpoly_changed(self,poly):"""This method is called whenever the pathpatch object is called."""# only copy the artist props to the line (except visibility)vis=self.line.get_visible()Artist.update_from(self.line,poly)self.line.set_visible(vis)# don't use the poly visibility statedefget_ind_under_point(self,event):"""        Return the index of the point closest to the event position or *None*        if no point is within ``self.epsilon`` to the event position.        """# display coordsxy=np.asarray(self.poly.xy)xyt=self.poly.get_transform().transform(xy)xt,yt=xyt[:,0],xyt[:,1]d=np.hypot(xt-event.x,yt-event.y)indseq,=np.nonzero(d==d.min())ind=indseq[0]ifd[ind]>=self.epsilon:ind=Nonereturninddefon_button_press(self,event):"""Callback for mouse button presses."""ifnotself.showverts:returnifevent.inaxesisNone:returnifevent.button!=1:returnself._ind=self.get_ind_under_point(event)defon_button_release(self,event):"""Callback for mouse button releases."""ifnotself.showverts:returnifevent.button!=1:returnself._ind=Nonedefon_key_press(self,event):"""Callback for key presses."""ifnotevent.inaxes:returnifevent.key=='t':self.showverts=notself.showvertsself.line.set_visible(self.showverts)ifnotself.showverts:self._ind=Noneelifevent.key=='d':ind=self.get_ind_under_point(event)ifindisnotNone:self.poly.xy=np.delete(self.poly.xy,ind,axis=0)self.line.set_data(zip(*self.poly.xy))elifevent.key=='i':xys=self.poly.get_transform().transform(self.poly.xy)p=event.x,event.y# display coordsforiinrange(len(xys)-1):s0=xys[i]s1=xys[i+1]d=dist_point_to_segment(p,s0,s1)ifd<=self.epsilon:self.poly.xy=np.insert(self.poly.xy,i+1,[event.xdata,event.ydata],axis=0)self.line.set_data(zip(*self.poly.xy))breakifself.line.stale:self.canvas.draw_idle()defon_mouse_move(self,event):"""Callback for mouse movements."""ifnotself.showverts:returnifself._indisNone:returnifevent.inaxesisNone:returnifevent.button!=1:returnx,y=event.xdata,event.ydataself.poly.xy[self._ind]=x,yifself._ind==0:self.poly.xy[-1]=x,yelifself._ind==len(self.poly.xy)-1:self.poly.xy[0]=x,yself.line.set_data(zip(*self.poly.xy))self.canvas.restore_region(self.background)self.ax.draw_artist(self.poly)self.ax.draw_artist(self.line)self.canvas.blit(self.ax.bbox)if__name__=='__main__':importmatplotlib.pyplotaspltfrommatplotlib.patchesimportPolygontheta=np.arange(0,2*np.pi,0.1)r=1.5xs=r*np.cos(theta)ys=r*np.sin(theta)poly=Polygon(np.column_stack([xs,ys]),animated=True)fig,ax=plt.subplots()ax.add_patch(poly)p=PolygonInteractor(ax,poly)ax.set_title('Click and drag a point to move it')ax.set_xlim(-2,2)ax.set_ylim(-2,2)plt.show()

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