python画球面投影_python – matplotlib：半球/楔形的自定义投影

我正在看matplotlib画廊中的custom projection示例 – 我正在尝试修改它以仅绘制南半球.我已将必要的[-pi / 2,pi / 2]限制调整为[-pi / 2,0].现在我一直在看：

def _gen_axes_patch(self):

"""

Override this method to define the shape that is used for the

background of the plot. It should be a subclass of Patch.

In this case, it is a Circle (that may be warped by the axes

transform into an ellipse). Any data and gridlines will be

clipped to this shape.

"""

#return Circle((0.5, 0.5), 0.5)

return Wedge((0.5,0.5), 0.5, 180, 360)

def _gen_axes_spines(self):

return {'custom_hammer':mspines.Spine.circular_spine(self,

(0.5, 0.5), 0.25)}

如您所见,我用Wedge替换了Circle补丁.这就是投影图目前的样子：

脊柱仍然遵循圆/椭圆 – 我如何指定我希望脊椎遵循楔形的边界？

我不确定如何最好地修改脊柱,所以任何帮助将非常感谢！

谢谢,

亚历克斯

解决方法:

只是为了记录,如果你还是python的新手,你肯定会直接进入游泳池的深处. (感谢你向前走！)

您正在做的事情需要对matplotlib的内部工作原理有相当详细的了解,matplotlib是一个相当复杂的库.

话虽如此,这是一个快速学习的好方法！

对于这样的事情,你需要了解事物结构的内部架构,而不仅仅是“公共”api.

对于大多数情况,你必须深入挖掘并“使用来源”.对于任何项目,内部工作的文档都是代码本身.

有人说,对于一个简单的案例,它非常简单.

import numpy as np

from matplotlib.projections.geo import HammerAxes

import matplotlib.projections as mprojections

from matplotlib.axes import Axes

from matplotlib.patches import Wedge

import matplotlib.spines as mspines

class LowerHammerAxes(HammerAxes):

name = 'lower_hammer'

def cla(self):

HammerAxes.cla(self)

Axes.set_xlim(self, -np.pi, np.pi)

Axes.set_ylim(self, -np.pi / 2.0, 0)

def _gen_axes_patch(self):

return Wedge((0.5, 0.5), 0.5, 180, 360)

def _gen_axes_spines(self):

path = Wedge((0, 0), 1.0, 180, 360).get_path()

spine = mspines.Spine(self, 'circle', path)

spine.set_patch_circle((0.5, 0.5), 0.5)

return {'wedge':spine}

mprojections.register_projection(LowerHammerAxes)

if __name__ == '__main__':

import matplotlib.pyplot as plt

fig = plt.figure()

ax = fig.add_subplot(111, projection='lower_hammer')

ax.grid(True)

plt.show()

让我们深入研究一下_get_axes_spines方法：

def _gen_axes_spines(self):

"""Return the spines for the axes."""

# Make the path for the spines

# We need the path, rather than the patch, thus the "get_path()"

# The path is expected to be centered at 0,0, with radius of 1

# It will be transformed by `Spine` when we initialize it

path = Wedge((0, 0), 1.0, 180, 360).get_path()

# We can fake a "wedge" spine without subclassing `Spine` by initializing

# it as a circular spine with the wedge path.

spine = mspines.Spine(self, 'circle', path)

# This sets some attributes of the patch object. In this particular

# case, what it sets happens to be approriate for our "wedge spine"

spine.set_patch_circle((0.5, 0.5), 0.5)

# Spines in matplotlib are handled in a dict (normally, you'd have top,

# left, right, and bottom, instead of just wedge). The name is arbitrary

return {'wedge':spine}

现在有一些问题：

>事物没有正确地在轴内居中

>轴补丁可以缩放一点,以适当占据轴内的空间.

>我们正在绘制整个地球的网格线,然后剪切它们.仅在我们的“较低”楔形内部绘制它们会更有效.

但是,当我们看看HammerAxes的结构时,你会注意到很多这些东西(特别是轴补丁的居中)被有效地硬编码到变换中. (正如他们在评论中提到的那样,它意味着是一个“玩具”的例子,并且假设你总是在处理整个地球,这使得转换中的数学变得更加简单.)

如果你想解决这些问题,你需要调整HammerAxes._set_lim_and_transforms中的几种变换.

但是,它的工作原理相当不错,所以我将把它作为练习留给读者. :)(请注意,这部分有点难,因为它需要详细了解matplotlib的转换.)

标签：projection,axes,python,matplotlib

来源： https://codeday.me/bug/20190902/1790401.html