如何在Python中设置Basemap的偏移量？

Question

下面是一个Basemap示例：

fig = plt.figure(figsize=(10,6))

ax = fig.add_subplot(121)
ax.set_title('Default')

# miller projection
map = Basemap(projection='mill',lon_0=180)
# plot coastlines, draw label meridians and parallels.
map.drawcoastlines()
map.drawparallels(np.arange(-90,90,30),labels=[1,0,0,0])
map.drawmeridians(np.arange(map.lonmin,map.lonmax+30,60),labels=[0,0,0,1])

ax = fig.add_subplot(122)
ax.set_title('Add offset')

# miller projection
map = Basemap(projection='mill',lon_0=180)
# plot coastlines, draw label meridians and parallels.
map.drawcoastlines()
map.drawparallels(np.arange(-90,90,30),labels=[1,0,0,0],xoffset=100,yoffset=100)
map.drawmeridians(np.arange(map.lonmin,map.lonmax+30,60),labels=[0,0,0,1],xoffset=100,yoffset=100)

我想在xlabel/ylabel和axis之间添加更多空间。 但是，添加xoffset和yoffset时，空间更小。在

Answer 1

basemap不再积极开发，但维护仍将持续一段时间。这意味着，由于其他包中的更改而中断的内容仍将被修复，但不会添加新功能。不管怎么说，修复部分可能需要一些时间，我猜平行线和子午线的xoffset特性正是受此影响。但是，查看basemap文档，xoffset和{}的功能描述如下

xoffset: label offset from edge of map in x-direction (default is 0.01 times width of map in map projection coordinates).

yoffset: label offset from edge of map in y-direction (default is 0.01 times height of map in map projection coordinates).

通过操作drawparallels()和drawmeridians()生成的Text对象很容易进行仿真。这些函数的结果存储在一个dict中，其中包含每个绘制的平行/子午线的一个元组列表，其中第二个包含文本标签。一个Text对象有一个get_position()和一个set_position()方法，结合轴限制和上述定义，可用于计算偏移量：

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

fig = plt.figure(figsize=(10,6))

ax = fig.add_subplot(121)
ax.set_title('Default')

# miller projection
map = Basemap(projection='mill',lon_0=180)
# plot coastlines, draw label meridians and parallels.
map.drawcoastlines()
map.drawparallels(np.arange(-90,90,30),labels=[1,0,0,0])
map.drawmeridians(np.arange(map.lonmin,map.lonmax+30,60),labels=[0,0,0,1])

ax = fig.add_subplot(122)
ax.set_title('Add offset')

# miller projection
map = Basemap(projection='mill',lon_0=180)
# plot coastlines, draw label meridians and parallels.
map.drawcoastlines()

##getting axes dimensions
x0,x1 = ax.get_xlim()
w = x1-x0
y0,y1 = ax.get_ylim()
h = y1-y0

xoffset = 0.05
yoffset = 0.05

result = map.drawparallels(np.arange(-90,90,30),labels=[1,0,0,0])
##
for key, (lines,texts) in result.items():
    for text in texts:
        x,y = text.get_position()
        text.set_position((x0-xoffset*w,y))


result = map.drawmeridians(np.arange(map.lonmin,map.lonmax+30,60),labels=[0,0,0,1])
for key, (lines,texts) in result.items():
    for text in texts:
        x,y = text.get_position()
        text.set_position((x,y0-yoffset*h))



plt.show()

结果图如下：