Matplotlib 获取图例标记的坐标

Question

第一次在这里提问。所以如果有什么不妥请告诉我。

所以我正在尝试创建一个综合生成图表的数据集，以训练神经网络为图表的不同元素找到边界框 - 图例框、图表标题、轴标签等。这就是我的部分我已经做到了。

接下来我需要创建一个从不同的图例条目到它们对应的数据点的映射。我需要为围绕不同句柄和文本的边界框创建注释，如下所示：

我试过查看文档，但找不到任何相关功能。使用 matplotlib.artist.getp() 查看图例的属性也让我一无所获。

fig, ax = plt.subplots(figsize=(12, 4))
x_vals = np.linspace(0, 5, 5)
y_vals = np.random.uniform(size=(5,))

ax.plot(x_vals, y_vals, label='line1')
ax.plot(x_vals, y_vals + np.random.randn(), label='line2')
leg = ax.legend()
ax.set_label('Label via method')

matplotlib.artist.getp(leg)

Output:
    agg_filter = None
    alpha = None
    animated = False
    bbox_to_anchor = TransformedBbox(     Bbox(x0=0.125, y0=0.125, x1=0...
    children = [<matplotlib.offsetbox.VPacker object at 0x7f3582d...
    clip_box = None
    clip_on = True
    clip_path = None
    contains = None
    default_handler_map = {<class 'matplotlib.container.StemContainer'>: <ma...
    figure = Figure(864x288)
    frame = FancyBboxPatch(640.55,203.64;60.625x33)
    frame_on = True
    gid = None
    label = 
    legend_handler_map = {<class 'matplotlib.container.StemContainer'>: <ma...
    lines = [<matplotlib.lines.Line2D object at 0x7f35834f4400...
    patches = <a list of 0 Patch objects>
    path_effects = []
    picker = None
    rasterized = None
    sketch_params = None
    snap = None
    texts = <a list of 2 Text objects>
    title = Text(0,0,'None')
    transform = IdentityTransform()
    transformed_clip_path_and_affine = (None, None)
    url = None
    visible = True
    window_extent = Bbox(x0=640.5500000000001, y0=203.64, x1=701.17500...
    zorder = 5

如有任何帮助，我们将不胜感激。请告诉我是否需要任何说明。谢谢

Answer 1

我花了整整 30 分钟四处寻找答案。我相信有更简单的方法，但这是我想出的一些方法，希望对您有所帮助

import matplotlib.pyplot as plt; plt.ion()
from matplotlib.patches import Rectangle as rect

fig, ax = plt.subplots()
ax.plot([0,1],[4,6],label='test')
leg = ax.legend(edgecolor='w', loc='upper left')
leg.get_frame().set_alpha(0)
line = leg.get_lines()[0]
plt.draw()
plt.pause(0.001)

#all of this is based on pixel coordinates in the figure
(lx0, ly0, lx1, ly1) = (leg.get_window_extent().x0,
                       leg.get_window_extent().y0,
                       leg.get_window_extent().x1,
                       leg.get_window_extent().y1)
(mx0, my0, mx1, my1) = (line.get_window_extent(fig).x0,
                       line.get_window_extent(fig).y0,
                       line.get_window_extent(fig).x1,
                       line.get_window_extent(fig).y1)
(ax0, ay0, ax1, ay1) = (ax.get_window_extent().x0,
                       ax.get_window_extent().y0,
                       ax.get_window_extent().x1,
                       ax.get_window_extent().y1)
#convert pixel coords to graphical coords
x0, x1 = ax.get_xlim()
y0, y1 = ax.get_ylim()
ratex = (x1-x0) / (ax1-ax0)
ratey = (y1-y0) / (ay1-ay0)
newx0 = (mx0 - ax0) * ratex + x0
newx1 = (mx1 - ax0) * ratex + x0
newy0 = (my0 - ay0) * ratey + y0 - 0.05
newy1 = (my1 - ay0) * ratey + y0 + 0.05
#box around legend marker
ax.add_patch(rect((newx0, newy0), newy1-newy0, newx1-newx0, edgecolor='k', alpha=0.5, facecolor='w'))
#convert pixel coords to graphical coords
tx0 = mx1
tx1 = lx1
ty0 = ly0
ty1 = ly1
newx0 = (tx0 - ax0) * ratex + x0
newx1 = (tx1 - ax0) * ratex + x0
newy0 = (ty0 - ay0) * ratey + y0
newy1 = (ty1 - ay0) * ratey + y0
#box around legend txt
ax.add_patch(rect((newx0, newy0), newy1-newy0, newx1-newx0, edgecolor='k', alpha=0.5, facecolor='w'))

这会产生以下情节：

我不是 100% 确定为什么这些框关闭，但您可以修改它以使其以某种方式工作...您也可以使用它来获取图例条目的坐标，并从这些坐标绘制矢量到相应数据线上的坐标

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