Question

使用python3和cartopy，具有以下代码：

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()

我明白了：

问题： 为了在保加利亚（或我在country.attributes['SOVEREIGNT']中指的任何其他国家/地区）上方显示红色的“ A ”，我该怎么写？当前标签根本没有显示，我不确定如何更改标签的字体。因此，似乎以下内容仅更改颜色，而不添加标签：

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

Answer 1

您可以检索几何图形的质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'])

在关注“保加利亚”的情况下，它看起来像：

编辑：

要使“依赖性”分开，请考虑使用admin_0_map_units而不是admin_0_map_countries，请参阅Natural Earth documentation 。

要突出显示较小的国家/地区，您可以使用以下方法向几何图形添加缓冲区：

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'])

您可以使用类似的方法分割特定的国家/地区，它使用Shapely在几何图形的中间执行相交。最终，将绘图和空间分析（拆分等）分成更多不同的步骤可能更“干净”。像这样混合使用它可能会使在其他情况下更难以重用代码。

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'])

如何在带有Python Cartopy的国家/地区贴上标签？

1 个答案: