译注:绘制地图时因为一些原因可能需要使用shapefile添加地图信息,比如很多软件中的关于中国的地图信息都不是很准确,当要明确标注中国边界信息时就会出问题。这次就介绍一下如何利用shp文件添加地图信息。
基本用法:
首先用一种最简单的方式绘制 shapefile
from mpl_toolkits.basemap import Basemap
import matplotlib.pyplot as plt
map = Basemap(llcrnrlon=-0.5,llcrnrlat=39.8,urcrnrlon=4.,urcrnrlat=43.,
resolution='i', projection='tmerc', lat_0 = 39.5, lon_0 = 1)
map.drawmapboundary(fill_color='aqua')
map.fillcontinents(color='#ddaa66',lake_color='aqua')
map.drawcoastlines()
map.readshapefile('../sample_files/comarques', 'comarques')
plt.show()
当然这些存在一些约束:
如图所示,结果仅是 polygons(polylines)的边界。如果要填充 polygons,可看后面的 填充 polygons 部分。
读取点数据
绘制点要复杂一些。首先,要读取 shapefile,然后使用 scatter, plot 或 matplotlib 函数进行绘制。
from mpl_toolkits.basemap import Basemap
import matplotlib.pyplot as plt
map = Basemap(llcrnrlon=-0.5,llcrnrlat=39.8,urcrnrlon=4.,urcrnrlat=43.,
resolution='i', projection='tmerc', lat_0 = 39.5, lon_0 = 1)
map.drawmapboundary(fill_color='aqua')
map.fillcontinents(color='#ddaa66',lake_color='aqua')
map.drawcoastlines()
map.readshapefile('../sample_files/comarques', 'comarques')
lightning_info = map.readshapefile('../sample_files/lightnings', 'lightnings')
print lightning_info
for info, lightning in zip(map.lightnings_info, map.lightnings):
if float(info['amplitude']) < 0:
marker = '_'
else:
marker = '+'
map.plot(lightning[0], lightning[1], marker=marker, color='m', markersize=8, markeredgewidth=2)
plt.show()
例子显示了一次雷暴过程中Catalonia 发生的闪电位置。
多边形信息
此例展示了如何使用 shapefile 属性选择一些 geometries
from mpl_toolkits.basemap import Basemap
import matplotlib.pyplot as plt
map = Basemap(llcrnrlon=-0.5,llcrnrlat=39.8,urcrnrlon=4.,urcrnrlat=43.,
resolution='i', projection='tmerc', lat_0 = 39.5, lon_0 = 1)
map.drawmapboundary(fill_color='aqua')
map.fillcontinents(color='#ddaa66',lake_color='aqua')
map.drawcoastlines()
map.readshapefile('../sample_files/comarques', 'comarques', drawbounds = False)
for info, shape in zip(map.comarques_info, map.comarques):
if info['nombre'] == 'Selva':
x, y = zip(*shape)
map.plot(x, y, marker=None,color='m')
plt.show()
填充多边形
基本的绘制并不会填充多边形,下面介绍以下如何绘制填充多边形:
from mpl_toolkits.basemap import Basemap
import matplotlib.pyplot as plt
from matplotlib.patches import Polygon
from matplotlib.collections import PatchCollection
from matplotlib.patches import PathPatch
import numpy as np
fig = plt.figure()
ax = fig.add_subplot(111)
map = Basemap(llcrnrlon=-0.5,llcrnrlat=39.8,urcrnrlon=4.,urcrnrlat=43.,
resolution='i', projection='tmerc', lat_0 = 39.5, lon_0 = 1)
map.drawmapboundary(fill_color='aqua')
map.fillcontinents(color='#ddaa66',lake_color='aqua')
map.drawcoastlines()
map.readshapefile('../sample_files/comarques', 'comarques', drawbounds = False)
patches = []
for info, shape in zip(map.comarques_info, map.comarques):
if info['nombre'] == 'Selva':
patches.append( Polygon(np.array(shape), True) )
ax.add_collection(PatchCollection(patches, facecolor= 'm', edgecolor='k', linewidths=1., zorder=2))
plt.show()
注1:http://shapelib.maptools.org/shp_api.html
http://stackoverflow.com/questions/15968762/shapefile-and-matplotlib-plot-polygon-collection-of-shapefile-coordinates