如何使用Python cartopy在地图上给国家标注？

Question

如何使用Python cartopy在地图上给国家标注？

10

使用Python3和Cartopy，有以下代码：

import matplotlib.pyplot as plt
import cartopy
import cartopy.io.shapereader as shpreader
import cartopy.crs as ccrs

ax = plt.axes(projection=ccrs.PlateCarree())
ax.add_feature(cartopy.feature.LAND)
ax.add_feature(cartopy.feature.OCEAN)
ax.add_feature(cartopy.feature.COASTLINE)
ax.add_feature(cartopy.feature.BORDERS, linestyle='-', alpha=.5)
ax.add_feature(cartopy.feature.LAKES, alpha=0.95)
ax.add_feature(cartopy.feature.RIVERS)

ax.set_extent([-150, 60, -25, 60])

shpfilename = shpreader.natural_earth(resolution='110m',
                                      category='cultural',
                                      name='admin_0_countries')

reader = shpreader.Reader(shpfilename)
countries = reader.records()

for country in countries:
    if country.attributes['SOVEREIGNT'] == "Bulgaria":
        ax.add_geometries(country.geometry, ccrs.PlateCarree(), facecolor=(0, 1, 0), label = "A")
    else:
        ax.add_geometries(country.geometry, ccrs.PlateCarree(), facecolor=(1, 1, 1), label = country.attributes['SOVEREIGNT'])
plt.rcParams["figure.figsize"] = (50,50)
plt.show()

我遇到了这个问题：

问题： 为了在保加利亚（或其他你在 country.attributes['SOVEREIGNT'] 中提到的国家）上方显示一个红色的"A"，我应该写什么？目前标签根本没有显示出来，我不确定如何更改标签的字体。因此，似乎以下代码只改变了颜色，而没有添加标签：

ax.add_geometries(country.geometry, ccrs.PlateCarree(), facecolor=(0, 1, 0), label = "A")

- Vityata

1个回答

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原文链接

- Rutger Kassies · Accepted Answer

您可以获取几何图形的重心并在该位置绘制文本：

import matplotlib.patheffects as PathEffects

for country in countries:

    if country.attributes['SOVEREIGNT'] == "Bulgaria":
        g = ax.add_geometries(country.geometry, ccrs.PlateCarree(), facecolor=(0, 1, 0), label="A")

        x = country.geometry.centroid.x        
        y = country.geometry.centroid.y

        ax.text(x, y, 'A', color='red', size=15, ha='center', va='center', transform=ccrs.PlateCarree(), 
                path_effects=[PathEffects.withStroke(linewidth=5, foreground="k", alpha=.8)])

    else:
        ax.add_geometries(country.geometry, ccrs.PlateCarree(), facecolor=(1, 1, 1), label = country.attributes['SOVEREIGNT'])

针对"保加利亚"所关注的地区，它看起来像是这样：

编辑：

如果要将"依赖项"分开，请考虑使用admin_0_map_units而非admin_0_map_countries，请参阅Natural Earth文档。

为了突出小国家/地区，您可以使用类似以下内容的几何缓冲区：

highlight = ['Singapore', 'Liechtenstein']

for country in countries:

    if country.attributes['NAME'] in highlight:

        if country.geometry.area < 2:
            geom = [country.geometry.buffer(2)]
        else:
            geom = [country.geometry]

        g = ax.add_geometries(geom, ccrs.PlateCarree(), facecolor=(0, 0.5, 0, 0.6), label="A", zorder=99)

        x = country.geometry.centroid.x        
        y = country.geometry.centroid.y

        ax.text(x, y+5, country.attributes['NAME'], color='red', size=14, ha='center', va='center', transform=ccrs.PlateCarree(), 
                path_effects=[PathEffects.withStroke(linewidth=3, foreground="k", alpha=.8)])

    else:
        ax.add_geometries(country.geometry, ccrs.PlateCarree(), facecolor=(1, 1, 1), label=country.attributes['NAME'])

您可以使用以下代码将特定国家进行分割，它使用Shapely在几何图形的中心执行交集。最终将绘图和空间分析（拆分等）分为更明确的步骤可能会更好。像这样混合可能会使代码更难被用于其他情况。

from shapely.geometry import LineString, MultiLineString

for country in countries:

    if country.attributes['NAME'] in 'China':

        # line at the centroid y-coord of the country
        l = LineString([(-180, country.geometry.centroid.y), 
                        (180, country.geometry.centroid.y)])

        north_poly = MultiLineString([l, north_line]).convex_hull
        south_poly = MultiLineString([l, south_line]).convex_hull

        g = ax.add_geometries([country.geometry.intersection(north_poly)], ccrs.PlateCarree(), facecolor=(0.8, 0.0, 0.0, 0.4), zorder=99)
        g = ax.add_geometries([country.geometry.intersection(south_poly)], ccrs.PlateCarree(), facecolor=(0.0, 0.0, 0.8, 0.4), zorder=99)

        x = country.geometry.centroid.x        
        y = country.geometry.centroid.y

        ax.text(x, y, country.attributes['NAME'], color='k', size=16, ha='center', va='center', transform=ccrs.PlateCarree(), 
                path_effects=[PathEffects.withStroke(linewidth=5, foreground="w", alpha=1)], zorder=100)

    else:
        ax.add_geometries(country.geometry, ccrs.PlateCarree(), facecolor=(1, 1, 1), label=country.attributes['NAME'])