如何更新 Matplotlib 上的形状？答案

【问题标题】：How to update a shape on Matplotlib?如何更新 Matplotlib 上的形状？
【发布时间】：2021-03-03 20:36:52
【问题描述】：

我有一个绘制在图像上的矩形。我想移动该形状，即更改其坐标，绘制新形状并删除旧形状（背景图像保持不变）

类似于此代码的内容。它显示了一个矩形三次，但我希望在绘制绿色形状时，删除红色的形状，蓝色的形状也是如此。当蓝色出现时去除绿色。

import matplotlib.pyplot as plt
import numpy as np

# Get an example image
image_file = r"image_splash.jpg"
img = plt.imread(image_file)

# Make some example data
x = np.array([475, 475, 675, 675, 475])
y = np.array([100, 200, 200, 100, 100])

# Create a figure
_dpi = 72
fig = plt.figure(1, figsize=(1000/_dpi, 1000/_dpi), dpi=_dpi)
ax = fig.add_subplot(1, 1, 1)
ax.set_aspect('equal')

# Show the image
ax.imshow(img)

# Now, loop through the offset array and update the shape 
# (This obviously doesnt work, it plots all three shapes)
rgb = ['r', 'g', 'b']
offset = [0, 150, 300]
plt.plot(x, y + offset[0], c=rgb[0]) # draw the red rect
plt.plot(x, y + offset[1], c=rgb[1]) # should remove the red and draw the green
plt.plot(x, y + offset[2], c=rgb[2]) # should remove the green and draw the blue

【问题讨论】：

标签： python matplotlib matplotlib-animation

【解决方案1】：

你可以试试matplotlib的动画api，如下图

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

fig, ax = plt.subplots()
xdata, ydata = [], []
(ln,) = plt.plot([], [], "r")

x = np.array([475, 475, 675, 675, 475])
y = np.array([100, 200, 200, 100, 100])
offset = [0, 150, 300]
colors = {
    0: "red",
    150: "green",
    300: "blue",
}


def init():
    ax.set_xlim(0, 1000)
    ax.set_ylim(0, 1000)
    return (ln,)


def update(_offset):
    ln.set_data(x, y + _offset)
    ln.set_color(colors[_offset])
    return (ln,)


def gety():
    for i in range(1000):
        yield offset[i % 3]


ani = FuncAnimation(fig, update, frames=gety(), init_func=init, blit=True)
plt.show()

【讨论】：