锚定艺术家对象
这个使用没有辅助类的锚定对象的示例在Matplotlib axes_grid1 Toolkit中找到。此版本的图与Simple Anchored Artists中的版本类似，但它仅使用matplotlib命名空间实现，没有其他工具包的帮助。
from matplotlib import pyplot as plt
from matplotlib.patches import Rectangle, Ellipse
from matplotlib.offsetbox import (
AnchoredOffsetbox, AuxTransformBox, DrawingArea, TextArea, VPacker)
class AnchoredText(AnchoredOffsetbox):
def __init__(self, s, loc, pad=0.4, borderpad=0.5,
prop=None, frameon=True):
self.txt = TextArea(s, minimumdescent=False)
super().__init__(loc, pad=pad, borderpad=borderpad,
child=self.txt, prop=prop, frameon=frameon)
def draw_text(ax):
"""
Draw a text-box anchored to the upper-left corner of the figure.
"""
at = AnchoredText("Figure 1a", loc='upper left', frameon=True)
at.patch.set_boxstyle("round,pad=0.,rounding_size=0.2")
ax.add_artist(at)
class AnchoredDrawingArea(AnchoredOffsetbox):
def __init__(self, width, height, xdescent, ydescent,
loc, pad=0.4, borderpad=0.5, prop=None, frameon=True):
self.da = DrawingArea(width, height, xdescent, ydescent)
super().__init__(loc, pad=pad, borderpad=borderpad,
child=self.da, prop=None, frameon=frameon)
def draw_circle(ax):
"""
Draw a circle in axis coordinates
"""
from matplotlib.patches import Circle
ada = AnchoredDrawingArea(20, 20, 0, 0,
loc='upper right', pad=0., frameon=False)
p = Circle((10, 10), 10)
ada.da.add_artist(p)
ax.add_artist(ada)
class AnchoredEllipse(AnchoredOffsetbox):
def __init__(self, transform, width, height, angle, loc,
pad=0.1, borderpad=0.1, prop=None, frameon=True):
"""
Draw an ellipse the size in data coordinate of the give axes.
pad, borderpad in fraction of the legend font size (or prop)
"""
self._box = AuxTransformBox(transform)
self.ellipse = Ellipse((0, 0), width, height, angle)
self._box.add_artist(self.ellipse)
super().__init__(loc, pad=pad, borderpad=borderpad,
child=self._box, prop=prop, frameon=frameon)
def draw_ellipse(ax):
"""
Draw an ellipse of width=0.1, height=0.15 in data coordinates
"""
ae = AnchoredEllipse(ax.transData, width=0.1, height=0.15, angle=0.,
loc='lower left', pad=0.5, borderpad=0.4,
frameon=True)
ax.add_artist(ae)
class AnchoredSizeBar(AnchoredOffsetbox):
def __init__(self, transform, size, label, loc,
pad=0.1, borderpad=0.1, sep=2, prop=None, frameon=True):
"""
Draw a horizontal bar with the size in data coordinate of the given
axes. A label will be drawn underneath (center-aligned).
pad, borderpad in fraction of the legend font size (or prop)
sep in points.
"""
self.size_bar = AuxTransformBox(transform)
self.size_bar.add_artist(Rectangle((0, 0), size, 0, ec="black", lw=1.0))
self.txt_label = TextArea(label, minimumdescent=False)
self._box = VPacker(children=[self.size_bar, self.txt_label],
align="center",
pad=0, sep=sep)
super().__init__(loc, pad=pad, borderpad=borderpad,
child=self._box, prop=prop, frameon=frameon)
def draw_sizebar(ax):
"""
Draw a horizontal bar with length of 0.1 in data coordinates,
with a fixed label underneath.
"""
asb = AnchoredSizeBar(ax.transData,
0.1,
r"1$^{\prime}$",
loc='lower center',
pad=0.1, borderpad=0.5, sep=5,
frameon=False)
ax.add_artist(asb)
ax = plt.gca()
ax.set_aspect(1.)
draw_text(ax)
draw_circle(ax)
draw_ellipse(ax)
draw_sizebar(ax)
plt.show()