图例框中文本和图标的对齐(matplotlib) [英] Alignment of text and the icon in the legend box (matplotlib)

问题描述

我想减小我的情节图例中文本的大小，以便 tikz 数字可以保持相对较大.问题是当我减小图例中字体的大小时，图例中的图标与文本之间的对齐会受到损害.我怎样才能再次配对它们?以下是测试:

I want to reduce the size of the text in the legend of my plot so that the tikz numbers could stay relatively large. The problem is when I reduce the size of the font in the legend, the alignment between the icon in the legend and the text get impaired. How can I pair them again? The following is a test:

import numpy as np
from  matplotlib import pyplot as plt
plt.rc('text', usetex = True)
font = {'family' : 'normal',
        'weight' : 'normal',
        'size'   : 25}
plt.rc('font', **font)
fig, ax = plt.subplots(1, 1)
a = np.arange(10)
b = np.random.randn(10)
ax.errorbar(a, b, yerr=0.5, fmt='o', color='g', ecolor='g', capthick=1, linestyle = '-', linewidth=2, elinewidth=1, label = "Test")
legend = plt.legend(bbox_to_anchor=(0., 1.02, 1., .102), loc=2, ncol=6, mode="expand", borderaxespad=0.2)
plt.setp(legend.get_texts(), fontsize='15') #legend 'list' fontsize
fig.set_size_inches(14.5, 10.5)
plt.savefig('/Users/Cupitor/Test.png')

如您在下图中所看到的，相对于左侧的绿色图形，图例中的文字不再处于中心位置:

As you can appreciate in the below picture the text in the legend is not any more central with respect to the green figure on its left:

推荐答案

我在Python 2.7和3.3，Ubuntu 15.04，matplotlib 1.4.2和使用Agg后端时遇到相同的问题.好像是通过plt.setp或者使用set_size方法直接设置了图例的文字艺术家的fontsize后，文字没有无论用于文本垂直对齐的选项('center'、'top'、'bottom'、'baseline')，都与其对应的句柄垂直居中对齐.

I am experiencing the same issue in Python 2.7 and 3.3, Ubuntu 15.04, matplotlib 1.4.2, and using the Agg backend. It seems that after setting directly the fontsize of the legend's text artists, either through plt.setp or using the set_size method, the text does not properly center-aligned vertically with its corresponding handle, no matter the option used for the vertical alignment of the text ('center', 'top', 'bottom', 'baseline').

我发现解决此问题的唯一方法是手动将文本的边框的高度与手柄的边框的高度对齐.根据您在 OP 中提供的代码，下面是一个示例，说明如何做到这一点:

The only way I've found to address this issue is to manually align the height of the bounding boxes of the text to the height of the bounding boxes of the handles. Based on the code you provided in your OP, below is an example that shows how this can be done:

import matplotlib as mpl
mpl.use('TkAgg')
import numpy as np
from  matplotlib import pyplot as plt

plt.close('all')

plt.rc('text', usetex = True)
font = {'family' : 'normal',
        'weight' : 'normal',
        'size'   : 25}
plt.rc('font', **font)

fig = plt.figure()
fig.set_size_inches(14.5, 10.5)
ax = fig.add_axes([0.1, 0.1, 0.85, 0.75])

#---- plot some data ----

ax.plot(np.arange(10), np.random.randn(10), 'rd', ms=15,
        label='The quick brown fox...')

ax.errorbar(np.arange(10), np.random.randn(10), yerr=0.5, fmt='o',
            color='g', ecolor='g', capthick=1,ls = '-', lw=2, elinewidth=1, 
            label = "... jumps over the lazy dog.")

#---- plot legend ----

legend = plt.legend(bbox_to_anchor=(0., 1.02, 1., 0.), handletextpad=0.3,
                    loc='lower left', ncol=6, mode="expand", borderaxespad=0,
                    numpoints=1, handlelength=0.5)

#---- adjust fontsize and va ----

plt.setp(legend.get_texts(), fontsize='15', va='bottom')

#---- set legend's label vert. pos. manually ----

h = legend.legendHandles
t = legend.texts
renderer = fig.canvas.get_renderer()

for i in range(len(h)):
    hbbox = h[i].get_window_extent(renderer) # bounding box of handle
    tbbox = t[i].get_window_extent(renderer) # bounding box of text

    x = tbbox.x0 # keep default horizontal position    
    y = (hbbox.height - tbbox.height) / 2. + hbbox.y0 # vertically center the
    # bbox of the text to the bbox of the handle.

    t[i].set_position((x, y)) # set new position of the text

plt.show(block=False)
plt.savefig('legend_text_va.png')

其结果是:

在 plt.setp 中设置 va='bottom' 似乎会产生更好的结果.我相信将垂直对齐方式设置为底部时，文本的bbox会更准确，但是我没有做进一步的研究来证实这一点.

Setting va='bottom' in plt.setp seems to yield better results. I believe that the bbox of the text is more accurate when the vertical alignment is set to bottom, but I haven't investigated further to confirm this.

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