%pylab inline
from JSAnimation.IPython_display import display_animation 
#http://nbviewer.ipython.org/url/jakevdp.github.io/downloads/notebooks/MagicTriangle.ipynb
from matplotlib import animation

from scipy.spatial import Delaunay

def mark_triangulation_angles(ax,triangulation):
    points = triangulation.points

    def normang(a):
        while(a>180):
            a = a - 360
        while (a<-180):
            a = a + 360
        return a
    
    def at2(v):
        return normang( np.rad2deg( np.arctan2(*v[::-1]) ) )

    def center_ang(a1,a2):
        c = (a1+a2)/2.0
        
        if (a1-a2) > 180:
            c += 180
            
        return normang(c)
    def dist_ang(a1,a2):
        d = np.abs(a1 - a2)
        if d > 180:
            d = 360 - d
        return d
    
    for triangle in triangulation.vertices:        
        ang0s = at2( points[triangle[1]]-points[triangle[0]] )
        ang0e = at2( points[triangle[2]]-points[triangle[0]] )
        
        ang1s = at2( points[triangle[0]]-points[triangle[1]] )
        ang1e = at2( points[triangle[2]]-points[triangle[1]] )
        
        ang2s = at2( points[triangle[0]]-points[triangle[2]] )
        ang2e = at2( points[triangle[1]]-points[triangle[2]] )

        angs = [ (ang0s,ang0e),(ang1s,ang1e), (ang2s,ang2e)]
        for i in range(len(angs)):
            
            s = min(angs[i])
            e = max(angs[i])
            
            angs[i] = (s,e)
            
            if e-s > 180:
                angs[i] = (e,s)
                
        for i,ang in enumerate(angs):
            p = matplotlib.patches.Arc(xy=points[triangle[i]],width=.4,height=.4,angle=0,theta1=ang[0],theta2=ang[1] )
            center = np.deg2rad( center_ang(ang[0], ang[1]) )
            xy_offset = np.array([ np.cos(center),np.sin(center) ])
            xy_offset *= 48
            
            s = r'$%4.2f^{\circ}$'%(dist_ang(ang[0],ang[1]))
            
            ax.annotate(s, xy=points[triangle[i]], xytext=xy_offset, xycoords='data', textcoords='offset points', va="center", ha="center",)
            p.set_color(ax._get_lines.color_cycle.next())
            ax.add_patch(p)

    
def make_frame(ax,leftness):
    height = .75
    #leftness = 1.5
    points = np.array([ [0,0],[2,0],[leftness,height],[leftness,-height]])
    tri = Delaunay(points)

    ax.triplot(points[:,0], points[:,1], tri.vertices.copy())
    ax.plot(points[:,0], points[:,1], 'o')
    ax.set_xlim(-.1,2.1)
    ax.set_ylim(-.8,.8)
    ax.set_aspect('equal')
    
    mark_triangulation_angles(ax,tri)
    ax.plot()

#make_frame(plt.gca(),1.6) #static frame

fig = plt.gcf()
ax = plt.gca()

Nframes = 10
def animate(frame):
    ax.clear()
    leftness = 1.5 + .3 * float(frame)/Nframes
    make_frame(ax,leftness)
    
anim = animation.FuncAnimation(fig, animate, frames=Nframes, interval=100)
display_animation(anim, default_mode='reflect')

pre_pad = 3
post_pad = 3

#indirection of frames hold, forward, hold, reverse
iframe = [0]*pre_pad + range(Nframes) + [Nframes-1]*post_pad + range(Nframes-1,0,-1)

def animate_as_gif(nframe):
    return animate(iframe[nframe])

    
anim = animation.FuncAnimation(fig, animate_as_gif,
                               frames=len(iframe), interval=100)
anim.save('delaunay_not_minimum_edge_length.gif', writer='imagemagick')