python - 如何创建 Basemap 实例并使用不同的 "overlays"重用它？

Question

我想创建一次 basemap 实例(因为它很昂贵)，然后将其与不同的contourf()叠加层一起重用。

澄清一下，我需要( basemap +轮廓1)和( basemap +轮廓2)，而不是( basemap +轮廓1+轮廓2)，这就是this question大约是。

有例子here和 here (来自同一作者的回复，相隔五年!)，但我无法让一个简单的可重用代码片段工作。

据此second example ，我的代码结构如下:

%matplotlib inline
import numpy as np
from mpl_toolkits.basemap import Basemap
import matplotlib.pyplot as plt


def get_basemap():
    fig = plt.figure('Background')
    fig.add_subplot(111)

    map_ = Basemap(resolution='c', projection='stere', width=12000000,
                   height=8000000, lat_ts=50, lat_0=50, lon_0=260.)
    map_.drawcoastlines()
    map_.drawmapboundary()
    map_.fillcontinents(zorder=-1)

    fig.canvas.draw()
    background = fig.canvas.copy_from_bbox(fig.bbox)

    return map_, background


def plot_thing1(map_, background, lats, lons, data):
    fig = plt.figure('Contourf', frameon=False)
    fig.add_subplot(111, frameon=False)

    fig.canvas.restore_region(background)    

    x, y = map_(*np.meshgrid(lons, lats))    
    map_.contourf(x, y, data, zorder=0)
    fig.show()


def plot_thing2(map_, background, lats, lons, ugrd, vgrd):
    fig = plt.figure('Quiver', frameon=False)
    fig.add_subplot(111, frameon=False)

    fig.canvas.restore_region(background)    

    x, y = map_(*np.meshgrid(lons, lats))    
    map_.quiver(x, y, ugrd, vgrd, zorder=0)
    fig.show()


min_lat, max_lat = 20, 70
min_lon, max_lon = 210, 310
lats = np.arange(min_lat, max_lat)
lons = np.arange(min_lon, max_lon)
shape = len(lats), len(lons)

# Run this once to get a reusable basemap
map_, background = get_basemap()

# Random data for thing1
data = np.random.rand(*shape)
plot_thing1(map_, background, lats, lons, data)

# Random data for thing2
ugrd, vgrd = np.random.rand(*shape), np.random.rand(*shape)
plot_thing2(map_, background, lats, lons, ugrd, vgrd)

但是 plot_thing1() 会生成两个“图”，一个具有 basemap 背景，另一个具有轮廓本身(而不是在一个图中将轮廓叠加在 basemap 上)。并且 plot_thing2() 只生成箭袋。

如何让它们出现在同一个地 block 上？ (并在 plot_thing1()、plot_thing2() 等中重用 basemap )这可能与附加到错误的事件图形/子图/轴的事物有关，但我无法理解 Basemap() 如何适应 matplotlib 层次结构。

Answer 1

下面保存了三张图像，单独的背景、带有等高线图的背景和带有箭袋的背景:

import numpy as np
from mpl_toolkits.basemap import Basemap
import matplotlib.pyplot as plt

def get_basemap():
    fig = plt.figure('Background')
    fig.add_subplot(111)
    map_ = Basemap(resolution='c', projection='stere', width=12000000,
                   height=8000000, lat_ts=50, lat_0=50, lon_0=260.)
    map_.drawcoastlines()
    map_.drawmapboundary()
    map_.fillcontinents(zorder=-1)
    return map_

def plot_thing1(map_, lats, lons, data):
    x, y = map_(*np.meshgrid(lons, lats))    
    c = map_.contourf(x, y, data, zorder=0)
    return c

def plot_thing2(map_, lats, lons, ugrd, vgrd):
    x, y = map_(*np.meshgrid(lons, lats))    
    q = map_.quiver(x, y, ugrd, vgrd, zorder=0)
    return q

min_lat, max_lat = 20, 70
min_lon, max_lon = 210, 310
lats = np.arange(min_lat, max_lat)
lons = np.arange(min_lon, max_lon)
shape = len(lats), len(lons)

# Run this once to get a reusable basemap
m  = get_basemap()
plt.savefig("background.png")
#Plot stuff on the axes
data = np.random.rand(*shape)
c = plot_thing1(m, lats, lons, data)
plt.savefig("thing1.png")
#remove the contourplot from the axes:
for member in c.collections:
    member.remove()
#Plot new stuff on the axes
ugrd, vgrd = np.random.rand(*shape), np.random.rand(*shape)
q = plot_thing2(m, lats, lons, ugrd, vgrd)
plt.savefig("thing2.png")
# to remove the quiver use
# q.remove()
plt.show()

作为解决方法，要直接在 jupyter 笔记本中显示保存的图像，您可以执行以下操作

from IPython.display import Image, display

listOfImageNames = ['background.png','thing1.png', 'thing2.png']

for fn in listOfImageNames:
    display(Image(filename=fn))