Python 在等高线图中突出显示用户选择的区域

Question

在 contourf 图中突出显示区域的最佳解决方案是什么？我希望背景的不透明度为 0.5，用户选择的区域是正常的。我怎样才能做到这一点？

Answer 1

在 Jake Vanderplas shows a way to draw a rectangle with a rectangular hole. The code can be adapted for your situation. The following example starts from a tutorial example中，突出显示第三个轮廓：

import numpy as np
import matplotlib.pyplot as plt
from matplotlib.path import Path
from matplotlib.patches import PathPatch

def DoubleRect(xy1, width1, height1,
               xy2, width2, height2, **kwargs):
    base = np.array([(0, 0), (0, 1), (1, 1), (1, 0), (0, 0)])
    verts = np.vstack([xy1 + (width1, height1) * base,
                       xy2 + (width2, height2) * base[::-1],
                       xy1])
    codes = 2 * ([Path.MOVETO] + 4 * [Path.LINETO]) + [Path.CLOSEPOLY]
    return PathPatch(Path(verts, codes), **kwargs)

origin = 'lower'
delta = 0.025
x = y = np.arange(-3.0, 3.01, delta)
X, Y = np.meshgrid(x, y)
Z1 = np.exp(-X ** 2 - Y ** 2)
Z2 = np.exp(-(X - 1) ** 2 - (Y - 1) ** 2)
Z = (Z1 - Z2) * 2

fig, ax = plt.subplots()
contours = ax.contourf(X, Y, Z, 10, cmap=plt.cm.turbo, origin=origin)
# contours.collections[2].set_color('deepskyblue') # mark one contour

# calculate (or get) the coordinates of the hole
bbox = contours.collections[2].get_paths()[0].get_extents()
hole_xy, hole_width, hole_height = bbox.p0, bbox.width, bbox.height

# find the coordinates of the surrounding rectangle
xmin, xmax = ax.get_xlim()
ymin, ymax = ax.get_ylim()
full_rect = plt.Rectangle((xmin, ymin), xmax - xmin, ymax - ymin, color='black', alpha=0.5)
ax.add_patch(full_rect)

# create a rectangle with a hole to clip the surrounding rectangle
mask = DoubleRect((xmin, ymin), xmax - xmin, ymax - ymin,
                  hole_xy, hole_width, hole_height,
                  facecolor='none', edgecolor='none')
ax.add_patch(mask)
full_rect.set_clip_path(mask)

plt.show()

除了使外部区域变暗，还可以对其进行阴影处理（类似于链接的 post）。这会将蒙版的边缘颜色设置为 'black'，并创建带有阴影线的完整矩形。

full_rect = plt.Rectangle((xmin, ymin), xmax - xmin, ymax - ymin, facecolor='none', edgecolor='black', hatch='//')

Python 在等高线图中突出显示用户选择的区域

Python highlight user chosen area in contourf plot

python

matplotlib

contourf