可拖动的Matplotlib散点图使用blitting进行动画绘制

Question

I recently asked a question about creating a draggable scatter and with the help of someone I was able to come up with a working example. See 'PathCollection' not iterable - creating a draggable scatter plot .

I'm now trying to use the DraggableScatter class I created with an animated plot using blitting.

I've tried to attach the DraggableScatter class in multiple places, eg, after initializing the scatter, in the init function and in the update function. In the first cases, the DraggableScatter's scatter is empty, which makes sense but obviously doesn't work. In the other two, the clicks seem not to be captured.

import matplotlib.pyplot as plt
from matplotlib.animation import FuncAnimation
import numpy as np

class DraggableScatter():

    epsilon = 5

    def __init__(self, scatter):
        self.scatter = scatter
        self._ind = None
        self.ax = scatter.axes
        self.canvas = self.ax.figure.canvas
        self.canvas.mpl_connect('button_press_event', self.button_press_callback)
        self.canvas.mpl_connect('button_release_event', self.button_release_callback)
        self.canvas.mpl_connect('motion_notify_event', self.motion_notify_callback)


    def get_ind_under_point(self, event):   
        xy = np.asarray(self.scatter.get_offsets())
        xyt = self.ax.transData.transform(xy)
        xt, yt = xyt[:, 0], xyt[:, 1]

        d = np.sqrt((xt - event.x)**2 + (yt - event.y)**2)
        ind = d.argmin()

        if d[ind] >= self.epsilon:
            ind = None

        return ind

    def button_press_callback(self, event):
        if event.inaxes is None:
            return
        if event.button != 1:
            return
        self._ind = self.get_ind_under_point(event)

    def button_release_callback(self, event):
        if event.button != 1:
            return
        self._ind = None

    def motion_notify_callback(self, event):
        if self._ind is None:
            return
        if event.inaxes is None:
            return
        if event.button != 1:
            return
        x, y = event.xdata, event.ydata
        xy = np.asarray(self.scatter.get_offsets())
        xy[self._ind] = np.array([x, y])        
        self.scatter.set_offsets(xy)
        self.canvas.draw_idle()


fig, ax = plt.subplots(1, 1)
scatter = ax.scatter([],[])


def init():
    ax.set_xlim(0, 1)
    ax.set_ylim(0, 1)

    return scatter,

def update(frame):
    scatter = ax.scatter(np.random.rand(10), np.random.rand(10), marker ='o')
    ds = DraggableScatter(scatter)
    return scatter,

ani = FuncAnimation(fig=fig, func=update, init_func=init, blit=True, interval=5000)
plt.show()

What is the right way to do this?

Answer 1

This works with the GTK3Cairo backend. (It does not work using TkAgg, Qt4Agg, Qt5Agg, GTK3Agg.)

Create the DraggableScatter once, then use ds.scatter.set_offsets to change the scatter point data inside the update function:

import matplotlib.pyplot as plt
from matplotlib.animation import FuncAnimation
import numpy as np

class DraggableScatter():

    epsilon = 5

    def __init__(self, scatter):
        self.scatter = scatter
        self._ind = None
        self.ax = scatter.axes
        self.canvas = self.ax.figure.canvas
        self.canvas.mpl_connect('button_press_event', self.button_press_callback)
        self.canvas.mpl_connect('button_release_event', self.button_release_callback)
        self.canvas.mpl_connect('motion_notify_event', self.motion_notify_callback)


    def get_ind_under_point(self, event):   
        xy = np.asarray(self.scatter.get_offsets())
        xyt = self.ax.transData.transform(xy)
        xt, yt = xyt[:, 0], xyt[:, 1]

        d = np.sqrt((xt - event.x)**2 + (yt - event.y)**2)
        ind = d.argmin()

        if d[ind] >= self.epsilon:
            ind = None

        return ind

    def button_press_callback(self, event):
        if event.inaxes is None:
            return
        if event.button != 1:
            return
        self._ind = self.get_ind_under_point(event)

    def button_release_callback(self, event):
        if event.button != 1:
            return
        self._ind = None

    def motion_notify_callback(self, event):
        if self._ind is None:
            return
        if event.inaxes is None:
            return
        if event.button != 1:
            return
        x, y = event.xdata, event.ydata
        xy = np.asarray(self.scatter.get_offsets())
        xy[self._ind] = np.array([x, y])        
        self.scatter.set_offsets(xy)
        self.canvas.draw_idle()


fig, ax = plt.subplots(1, 1)
scatter = ax.scatter(np.random.rand(10), np.random.rand(10), marker ='o')
ds = DraggableScatter(scatter)

def init():
    ax.set_xlim(0, 1)
    ax.set_ylim(0, 1)
    return ds.scatter,

def update(frame, ds):
    x, y = np.random.rand(10), np.random.rand(10)
    ds.scatter.set_offsets(np.column_stack([x, y]))
    return ds.scatter,

ani = FuncAnimation(fig=fig, func=update, init_func=init, fargs=[ds], blit=True, 
                    interval=5000)
plt.show()