python - Matplotlib 绘制数百个矩形轮廓

Question

我想使用 matplotlib 绘制一些矩形轮廓。问题是，我需要大量的矩形，所以绘制矩形的“正常”方式非常慢。我使用 How to speed up plot... 解决了这个问题。问题是，我无法再使用 fill=None 绘制矩形的边缘。或edgecolor=...和facecolor=None .

查看我的代码的玩具示例:

import numpy as np
import matplotlib.pyplot as plt
from matplotlib.collections import PatchCollection
from matplotlib.patches import Rectangle


def plot_rectangle_from_area(area, color):
    """Plot a rectangle for a given area with color"""
    return Rectangle(xy=(area["min_x"], area["min_y"]), width=area["max_x"] - area["min_x"],
                     height=area["max_y"] - area["min_y"],
                     fill=None)  #  linewidth=0, edgecolor=color, facecolor=None, zorder=100, alpha=0, 


sample_areas = [{"min_x": -1, "max_x": 0.4, "min_y": 0.7, "max_y": 1},
                {"min_x": 0.5, "max_x": 1, "min_y": 0.1, "max_y": 0.5}]
rectangles = []

fig, ax = plt.subplots()
# ... print some contour via meshgrid

if sample_areas:
    for area_i in sample_areas:
        rectangles.append(plot_rectangle_from_area(area_i, color="r"))
#   ... some more cases

# Append the rectangles all at once instead of on their own, see:
# https://stackoverflow.com/questions/33905305/how-to-speed-up-the-plot-of-a-large-number-of-rectangles-with-matplotlib
ax.add_collection(PatchCollection(rectangles))

# ... legend, save, grid, ...
plt.show()

首先，我为所有矩形创建一个数组，附加到它并使用 PatchCollection 来绘制它 1 。下面的示例执行完全相同的操作，只是没有 PatchCollection 并且工作正常。

import numpy as np
import matplotlib.pyplot as plt
from matplotlib.collections import PatchCollection
from matplotlib.patches import Rectangle


def plot_rectangle_from_area(area, color):
    """Plot a rectangle from given area"""
    return Rectangle(xy=(area["min_x"], area["min_y"]), width=area["max_x"] - area["min_x"],
                     height=area["max_y"] - area["min_y"],
                     fill=None)  #  linewidth=0, edgecolor=color, facecolor=None, zorder=100, alpha=0, 

sample_areas = [{"min_x": -1, "max_x": 0.4, "min_y": 0.7, "max_y": 1},
                {"min_x": 0.5, "max_x": 1, "min_y": 0.1, "max_y": 0.5}]

fig, ax = plt.subplots()

if sample_areas:
    for area_i in sample_areas:
        ax.add_patch(plot_rectangle_from_area(area_i, color="r"))
plt.show()

这是我用这两个代码创建的一些图。左边是使用慢速方法得到的期望结果，右边是我使用 PatchCollection 得到的结果:

我尝试了填充、边缘颜色、面部颜色的多种组合，甚至还尝试了 here 中 zorder 的建议。 .

是否可以使用“快速”方式创建矩形并仅显示边框？

Answer 1

是的 - 查看 PatchCollection 的文档，有一个名为 match_original 的参数，当 True 时，该参数将设置面片的属性以匹配原始矩形的属性。

所以只需更改

ax.add_collection(PatchCollection(rectangles))

到

ax.add_collection(PatchCollection(rectangles, match_original=True))