使用Pillow无法调用Futura粗体字体？求解决方案

问题场景 #

在macOS Monterey系统上，使用Pillow 9.4.0 + Python 3.11开发时，尝试为图片添加Futura字体的粗体文本，Font Book和Preview显示该字体存在粗体变体，但执行以下代码触发OSError，提示该字体不是可变字体：

title_font = ImageFont.truetype("Supplemental/Futura.ttc")
title_font.set_variation_by_name("bold")

报错堆栈 #

../helper/ThumbnailCreator.py:38: in add_text
    title_font.set_variation_by_name("bold")
../../venv311/lib/python3.11/site-packages/PIL/ImageFont.py:834: in set_variation_by_name
    names = self.get_variation_names()
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 

self = <PIL.ImageFont.FreeTypeFont object at 0x106c08dd0>

    def get_variation_names(self):
        """
        :returns: A list of the named styles in a variation font.
        :exception OSError: If the font is not a variation font.
        """
        try:
>           names = self.font.getvarnames()
E           OSError: invalid argument

../../venv311/lib/python3.11/site-packages/PIL/ImageFont.py:823: OSError

Pillow环境检测信息 #

python -m PIL
--------------------------------------------------------------------
Pillow 9.4.0
Python 3.11.0rc1 (v3.11.0rc1:41cb07120b, Aug  5 2022, 11:44:46) [Clang 13.0.0 (clang-1300.0.29.30)]
--------------------------------------------------------------------
Python modules loaded from /Users/jb/PycharmProjects/blog_content_creatronix/venv311/lib/python3.11/site-packages/PIL
Binary modules loaded from /Users/jb/PycharmProjects/blog_content_creatronix/venv311/lib/python3.11/site-packages/PIL
--------------------------------------------------------------------
--- PIL CORE support ok, compiled for 9.4.0
--- TKINTER support ok, loaded 8.6
--- FREETYPE2 support ok, loaded 2.12.1
--- LITTLECMS2 support ok, loaded 2.14
--- WEBP support ok, loaded 1.3.0
--- WEBP Transparency support ok
--- WEBPMUX support ok
--- WEBP Animation support ok
--- JPEG support ok, compiled for libjpeg-turbo 2.1.4
--- OPENJPEG (JPEG2000) support ok, loaded 2.5.0
--- ZLIB (PNG/ZIP) support ok, loaded 1.2.13
--- LIBTIFF support ok, loaded 4.5.0
*** RAQM (Bidirectional Text) support not installed
*** LIBIMAGEQUANT (Quantization method) support not installed
--- XCB (X protocol) support ok
--------------------------------------------------------------------
BLP
Extensions: .blp
Features: open, save, encode
--------------------------------------------------------------------
BMP image/bmp
Extensions: .bmp
Features: open, save
--------------------------------------------------------------------
BUFR
Extensions: .bufr
Features: open, save
--------------------------------------------------------------------
CUR
Extensions: .cur
Features: open
--------------------------------------------------------------------
DCX
Extensions: .dcx
Features: open
--------------------------------------------------------------------
DDS
Extensions: .dds
Features: open, save
--------------------------------------------------------------------
DIB image/bmp
Extensions: .dib
Features: open, save
--------------------------------------------------------------------
EPS application/postscript
Extensions: .eps, .ps
Features: open, save
--------------------------------------------------------------------
FITS
Extensions: .fit, .fits
Features: open, save
--------------------------------------------------------------------
FLI
Extensions: .flc, .fli
Features: open
--------------------------------------------------------------------
FTEX
Extensions: .ftc, .ftu
Features: open
--------------------------------------------------------------------
GBR
Extensions: .gbr
Features: open
--------------------------------------------------------------------
GIF image/gif
Extensions: .gif
Features: open, save, save_all
--------------------------------------------------------------------
GRIB
Extensions: .grib
Features: open, save
--------------------------------------------------------------------
HDF5
Extensions: .h5, .hdf
Features: open, save
--------------------------------------------------------------------
ICNS image/icns
Extensions: .icns
Features: open, save
--------------------------------------------------------------------
ICO image/x-icon
Extensions: .ico
Features: open, save
--------------------------------------------------------------------
IM
Extensions: .im
Features: open, save
--------------------------------------------------------------------
IMT
Features: open
--------------------------------------------------------------------
IPTC
Extensions: .iim
Features: open
--------------------------------------------------------------------
JPEG image/jpeg
Extensions: .jfif, .jpe, .jpeg, .jpg
Features: open, save
--------------------------------------------------------------------
JPEG2000 image/jp2
Extensions: .j2c, .j2k, .jp2, .jpc, .jpf, .jpx
Features: open, save
--------------------------------------------------------------------
MCIDAS
Features: open
--------------------------------------------------------------------
MPEG video/mpeg
Extensions: .mpeg, .mpg
Features: open
--------------------------------------------------------------------
MSP
Extensions: .msp
Features: open, save, decode
--------------------------------------------------------------------
PCD
Extensions: .pcd
Features: open
--------------------------------------------------------------------
PCX image/x-pcx
Extensions: .pcx
Features: open, save
--------------------------------------------------------------------
PIXAR
Extensions: .pxr
Features: open
--------------------------------------------------------------------
PNG image/png
Extensions: .apng, .png
Features: open, save, save_all
--------------------------------------------------------------------
PPM image/x-portable-anymap
Extensions: .pbm, .pgm, .pnm, .ppm
Features: open, save
--------------------------------------------------------------------
PSD image/vnd.adobe.photoshop
Extensions: .psd
Features: open
--------------------------------------------------------------------
SGI image/sgi
Extensions: .bw, .rgb, .rgba, .sgi
Features: open, save
--------------------------------------------------------------------
SPIDER
Features: open, save
--------------------------------------------------------------------
SUN
Extensions: .ras
Features: open
--------------------------------------------------------------------
TGA image/x-tga
Extensions: .icb, .tga, .vda, .vst
Features: open, save
--------------------------------------------------------------------
TIFF image/tiff
Extensions: .tif, .tiff
Features: open, save, save_all
--------------------------------------------------------------------
WEBP image/webp
Extensions: .webp
Features: open, save, save_all
--------------------------------------------------------------------
WMF
Extensions: .emf, .wmf
Features: open, save
--------------------------------------------------------------------
XBM image/xbm
Extensions: .xbm
Features: open, save
--------------------------------------------------------------------
XPM image/xpm
Extensions: .xpm
Features: open
--------------------------------------------------------------------
XVTHUMB
Features: open
--------------------------------------------------------------------

解决方法 #

原因说明 #

Futura.ttc是TrueType字体集合（TTC），而非可变字体。可变字体支持通过set_variation_by_name动态调整样式，但TTC是将多个独立字体打包在一个文件中，每个样式（如粗体）都是独立的字体实例，无法用可变字体的方式调用。

方案1：通过索引指定粗体字体 #

TTC文件中的每个字体都有对应的索引，直接指定索引加载粗体变体：

# 尝试index=1或其他数值，根据TTC内的字体顺序调整
title_font = ImageFont.truetype("Supplemental/Futura.ttc", index=1)

可通过fc-list命令（需先通过brew安装fontconfig：brew install fontconfig）查看TTC内的字体信息：

fc-list /Library/Fonts/Supplemental/Futura.ttc

方案2：直接调用粗体字体名称 #

如果知道Futura粗体的具体字体名，直接指定名称加载：

title_font = ImageFont.truetype("Futura Bold")

方案3：使用绝对路径加载 #

直接指定字体文件的绝对路径，避免路径解析问题：

title_font = ImageFont.truetype("/Library/Fonts/Supplemental/Futura.ttc", index=1)

内容的提问来源于stack exchange，提问作者Joern Boegeholz