如何保存 matplotlib 动画的最后一张图片？

Question

我想知道如何FuncAnimation在 Python 3 中保存 a 的最后一张图像。这是一些代码：

import matplotlib.animation

from mpl_toolkits.mplot3d import Axes3D

ani = matplotlib.animation.FuncAnimation(fig, _update_2d_graph, frames=9, interval=600, repeat_delay=5000, blit=False)

ani.save(output_dir, writer="imagemagick")

其中_update_2d_graph是一个函数，根据帧数提供不同的点偏移量：

def _update_2d_graph(num):

    x_updated = np.hstack((pos_gt.x[:num].tolist(),pos_pred.x[:num].tolist()))

    y_updated = np.hstack((pos_gt.y[:num].tolist(),pos_pred.y[:num].tolist()))

    paths_gt = []

    paths_ped = []

    for i in range(num):

        marker_gt = mmarkers.MarkerStyle('o')

        marker_ped = mmarkers.MarkerStyle('x')

        path_gt = marker_gt.get_path().transformed(marker_gt.get_transform())

        path_ped = marker_ped.get_path().transformed(marker_ped.get_transform())

        paths_gt.append(path_gt)

        paths_ped.append(path_ped)

    graph._paths = np.concatenate([paths_gt, paths_ped])

    graph.set_facecolors(np.concatenate([colors[:num], colors[:num]]))

    graph.set_edgecolors(np.concatenate([colors[:num], colors[:num]]))

    graph.set_offsets(np.hstack((y_updated[:, np.newaxis], x_updated[:, np.newaxis])))

而不是保存整个动画（例如作为 .gif 文件），我想保存动画的最后一个时间步的 .png。 是否可以访问动画对象中的最后一帧？

我不想调用，_update_2d_graph(9)因为这个调用已经被动画对象执行了，我也不想通过另一个FuncAnimation调用重新迭代整个 9 帧。

Answer 1

实际上，我最初的测试表明，在运行动画后保存图形确实会保存最后一帧的状态。你能测试它以确认吗？ani = matplotlib.animation.FuncAnimation(fig, _update_2d_graph, frames=9, interval=600, repeat_delay=5000, blit=False)ani.save(output_dir, writer="imagemagick")fig.savefig('last_frame.png')我使用了动画 3D 随机游走示例中的代码：import numpy as npimport matplotlib.pyplot as pltimport mpl_toolkits.mplot3d.axes3d as p3import matplotlib.animation as animation# Fixing random state for reproducibilitynp.random.seed(19680801)def Gen_RandLine(length, dims=2):    """    Create a line using a random walk algorithm    length is the number of points for the line.    dims is the number of dimensions the line has.    """    lineData = np.empty((dims, length))    lineData[:, 0] = np.random.rand(dims)    for index in range(1, length):        # scaling the random numbers by 0.1 so        # movement is small compared to position.        # subtraction by 0.5 is to change the range to [-0.5, 0.5]        # to allow a line to move backwards.        step = ((np.random.rand(dims) - 0.5) * 0.1)        lineData[:, index] = lineData[:, index - 1] + step    return lineDatadef update_lines(num, dataLines, lines):    for line, data in zip(lines, dataLines):        # NOTE: there is no .set_data() for 3 dim data...        line.set_data(data[0:2, :num])        line.set_3d_properties(data[2, :num])    return lines# Attaching 3D axis to the figurefig = plt.figure()ax = p3.Axes3D(fig)# Fifty lines of random 3-D linesdata = [Gen_RandLine(25, 3) for index in range(50)]# Creating fifty line objects.# NOTE: Can't pass empty arrays into 3d version of plot()lines = [ax.plot(dat[0, 0:1], dat[1, 0:1], dat[2, 0:1])[0] for dat in data]# Setting the axes propertiesax.set_xlim3d([0.0, 1.0])ax.set_xlabel('X')ax.set_ylim3d([0.0, 1.0])ax.set_ylabel('Y')ax.set_zlim3d([0.0, 1.0])ax.set_zlabel('Z')ax.set_title('3D Test')# Creating the Animation objectline_ani = animation.FuncAnimation(fig, update_lines, 25, fargs=(data, lines),                                   interval=50, blit=False, repeat=True)### HERE ARE THE ONLY LINES I ADDED ####line_ani.save('./test.gif', writer='imagemagick')fig.savefig('./test.png') 文件 test.gif文件 test.png