python - 可拖动的 Matplotlib 散点图，带有使用 blitting 的动画图

Question

我最近问了一个关于创建可拖动散点图的问题，在某人的帮助下，我想出了一个可行的例子。请参阅'PathCollection' not iterable - 创建可拖动的散点图。

我现在正在尝试使用我创建的 DraggableScatter 类和使用 blitting 的动画情节。

我尝试在多个地方附加 DraggableScatter 类，例如，在初始化散点图之后，在 init 函数和更新函数中。在第一种情况下，DraggableScatter 的 scatter 是空的，这是有道理的，但显然不起作用。在另外两个中，点击似乎没有被捕获。

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()

这样做的正确方法是什么？

标签： pythonpython-3.xmatplotlib

Answer 1

这适用于 GTK3Cairo 后端。（它不适用于 TkAgg、Qt4Agg、Qt5Agg、GTK3Agg。）

创建DraggableScatter一次，然后用于ds.scatter.set_offsets更改update函数内部的散点数据：

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()