How can I fix matplotlib detecting wrong font weights?

debugcn Published at Dev

physicsPyUser

I downloaded fonts from Google Fonts which I want to use for my thesis and all plots, namely the Alegreya font family. After installing the fonts to $HOME/.fonts I removed .cache/matplotlib/fontList.cache and created a plot with the new font.family = 'Alegreya Sans' in the rcParams. Unfortunately, matplotlib detects the Thin font of Alegreya Sans as the Regular one. The false detection is illustrated by the following minimal example:

import matplotlib.font_manager

weights = ['ultralight', 'light', 'normal', 'regular', 'book', 'medium', 
           'roman', 'semibold', 'demibold', 'demi', 'bold', 'heavy', 
           'extra bold', 'black']

print 'weight'+6*' ', 'file name', '\n'+70*'-'
for weight in weights:
    fprops = matplotlib.font_manager.FontProperties(family='Alegreya Sans', 
                                                    weight=weight)
    print weight+(12-len(weight))*' ', matplotlib.font_manager.findfont(fprops)

Output:

weight       file name 
----------------------------------------------------------------------
ultralight   /hmi/kme/.fonts/Alegreya_Sans/AlegreyaSans-Light.ttf
light        /hmi/kme/.fonts/Alegreya_Sans/AlegreyaSans-Light.ttf
normal       /hmi/kme/.fonts/Alegreya_Sans/AlegreyaSans-Thin.ttf
regular      /hmi/kme/.fonts/Alegreya_Sans/AlegreyaSans-Thin.ttf
book         /hmi/kme/.fonts/Alegreya_Sans/AlegreyaSans-Thin.ttf
medium       /hmi/kme/.fonts/Alegreya_Sans/AlegreyaSans-Medium.ttf
roman        /hmi/kme/.fonts/Alegreya_Sans/AlegreyaSans-Medium.ttf
semibold     /hmi/kme/.fonts/Alegreya_Sans/AlegreyaSans-ExtraBold.ttf
demibold     /hmi/kme/.fonts/Alegreya_Sans/AlegreyaSans-ExtraBold.ttf
demi         /hmi/kme/.fonts/Alegreya_Sans/AlegreyaSans-ExtraBold.ttf
bold         /hmi/kme/.fonts/Alegreya_Sans/AlegreyaSans-ExtraBold.ttf
heavy        /hmi/kme/.fonts/Alegreya_Sans/AlegreyaSans-ExtraBold.ttf
extra bold   /hmi/kme/.fonts/Alegreya_Sans/AlegreyaSans-ExtraBold.ttf
black        /hmi/kme/.fonts/Alegreya_Sans/AlegreyaSans-Black.ttf

How can this be fixed and why does it happen? Thanks in advance!

Edit:

Of course, there are more files in the folder /hmi/kme/.fonts/Alegreya_Sans/

A complete list:

AlegreyaSans-BlackItalic.ttf
AlegreyaSans-BoldItalic.ttf
AlegreyaSans-ExtraBoldItalic.ttf
AlegreyaSans-Italic.ttf
AlegreyaSans-Light.ttf
AlegreyaSans-Medium.ttf
AlegreyaSans-ThinItalic.ttf
AlegreyaSans-Black.ttf
AlegreyaSans-Bold.ttf
AlegreyaSans-ExtraBold.ttf
AlegreyaSans-LightItalic.ttf
AlegreyaSans-MediumItalic.ttf
AlegreyaSans-Regular.ttf
AlegreyaSans-Thin.ttf

My System

OpenSuse 13.1
python 2.7
matplotlib version 1.4.3

physicsPyUser

I fixed the problem manually with a work-around. Anyhow this seems to be a bug. As tom mentioned, I copied all fonts to $HOME/.fonts without subdirectories. This changed the output from the script I gave in the question. To find out what's wrong I tried to print all combinations of weight and style of Alegreya and Alegreya Sans in the following way:

import matplotlib
matplotlib.use('Qt4Agg')
print matplotlib.get_backend()
import matplotlib.pyplot as plt

alignment = {'horizontalalignment':'center', 'verticalalignment':'baseline'}
alegreya_weights = { 'Alegreya': ['regular', 'bold', 'black'],
                     'Alegreya Sans': ['ultralight', 'light', 'regular', 
                                       'medium', 'bold', 'extra bold', 
                                       'black'] }
styles = ['normal', 'italic']

combinations = []
for family in alegreya_weights.keys():
    for style in styles:
        for weight in alegreya_weights[family]:
            combinations.append((family, weight, style))
N = len(combinations)

def textPlot(ax, i, N, family, weight, style):
    y = 1.-(1./float(N)) -float(i)/(float(N)+1)
    ax.text(0.5, y, family+' '+weight+' '+style, 
            family=family, weight=weight, style = style, 
            fontsize = 30, **alignment)

fig = plt.figure(figsize=(8, .7*N), frameon=False)
ax = plt.gca()
ax.axis('off')
plt.xlim((0.,1.))
plt.ylim((0.,1.))

for i,c in enumerate(combinations):
    textPlot(ax, i, N, c[0], c[1], c[2])

plt.show()

It turned out that only AlegreyaSans-Regular.ttf was replaced by AlegreyaSans-Thin.ttf. I couldn't find out if this is due to the word "Thin", which is referred to as "ultralight" in matplotlib-syntax. I replaced "AlegreyaSans-Thin.ttf" by "AlegreyaSans-Regular.ttf" in $HOME/.cache/matplotlib/fontList.cache to solved the problem.

Now the following image results from the script above. Thin (ultralight) is not detected.

Thanks to tom for any help.

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edited at2021-07-11

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