如何让Ghostscript 10仅加载一次字体，恢复Ghostscript 9的高效性能？

问题现象 #

在Debian 11/Bullseye系统中，用Ghostscript 9.53.3处理example.pdf时，字体仅加载一次，性能正常：

bullseye$ gs -sOutputFile=page-%04d.png -dNOPAUSE -dBATCH -sDEVICE=png16m -r108 example.pdf   
GPL Ghostscript 9.53.3 (2020-10-01)
Copyright (C) 2020 Artifex Software, Inc.  All rights reserved.
This software is supplied under the GNU AGPLv3 and comes with NO WARRANTY:
see the file COPYING for details.
Processing pages 1 through 8154.
Page 1
Loading NimbusSans-Bold font from /usr/share/ghostscript/9.53.3/Resource/Font/NimbusSans-Bold... 4466348 2932264 35444440 32057018 4 done.
Page 2
Page 3
Page 4
Page 5
Page 6
Page 7
Page 8
...

但在Debian 12/Bookworm系统中，Ghostscript 10.0.0会反复加载字体，占用大量资源，性能远低于旧版本：

bookworm$ gs -sOutputFile=page-%04d.png -dNOPAUSE -dBATCH -sDEVICE=png16m -r108 example.pdf
GPL Ghostscript 10.0.0 (2022-09-21)
Copyright (C) 2022 Artifex Software, Inc.  All rights reserved.
This software is supplied under the GNU AGPLv3 and comes with NO WARRANTY:
see the file COPYING for details.
Processing pages 1 through 8154.
Page 1
Loading font Helvetica-Bold (or substitute) from /usr/share/ghostscript/10.00.0/Resource/Font/NimbusSans-Bold
Loading font Helvetica-Bold (or substitute) from /usr/share/ghostscript/10.00.0/Resource/Font/NimbusSans-Bold
Loading font Helvetica-Bold (or substitute) from /usr/share/ghostscript/10.00.0/Resource/Font/NimbusSans-Bold
Loading font Helvetica-Bold (or substitute) from /usr/share/ghostscript/10.00.0/Resource/Font/NimbusSans-Bold
Loading font Helvetica-Bold (or substitute) from /usr/share/ghostscript/10.00.0/Resource/Font/NimbusSans-Bold
Loading font Helvetica-Bold (or substitute) from /usr/share/ghostscript/10.00.0/Resource/Font/NimbusSans-Bold
Loading font Helvetica-Bold (or substitute) from /usr/share/ghostscript/10.00.0/Resource/Font/NimbusSans-Bold
Loading font Helvetica-Bold (or substitute) from /usr/share/ghostscript/10.00.0/Resource/Font/NimbusSans-Bold
Loading font Helvetica-Bold (or substitute) from /usr/share/ghostscript/10.00.0/Resource/Font/NimbusSans-Bold
Loading font Helvetica-Bold (or substitute) from /usr/share/ghostscript/10.00.0/Resource/Font/NimbusSans-Bold
Loading font Helvetica-Bold (or substitute) from /usr/share/ghostscript/10.00.0/Resource/Font/NimbusSans-Bold
Loading font Helvetica-Bold (or substitute) from /usr/share/ghostscript/10.00.0/Resource/Font/NimbusSans-Bold
Loading font Helvetica-Bold (or substitute) from /usr/share/ghostscript/10.00.0/Resource/Font/NimbusSans-Bold
Page 2
Loading font Helvetica-Bold (or substitute) from /usr/share/ghostscript/10.00.0/Resource/Font/NimbusSans-Bold
Loading font Helvetica-Bold (or substitute) from /usr/share/ghostscript/10.00.0/Resource/Font/NimbusSans-Bold
Loading font Helvetica-Bold (or substitute) from /usr/share/ghostscript/10.00.0/Resource/Font/NimbusSans-Bold
Loading font Helvetica-Bold (or substitute) from /usr/share/ghostscript/10.00.0/Resource/Font/NimbusSans-Bold
Loading font Helvetica-Bold (or substitute) from /usr/share/ghostscript/10.00.0/Resource/Font/NimbusSans-Bold
Loading font Helvetica-Bold (or substitute) from /usr/share/ghostscript/10.00.0/Resource/Font/NimbusSans-Bold
Loading font Helvetica-Bold (or substitute) from /usr/share/ghostscript/10.00.0/Resource/Font/NimbusSans-Bold
Loading font Helvetica-Bold (or substitute) from /usr/share/ghostscript/10.00.0/Resource/Font/NimbusSans-Bold
Loading font Helvetica-Bold (or substitute) from /usr/share/ghostscript/10.00.0/Resource/Font/NimbusSans-Bold
Loading font Helvetica-Bold (or substitute) from /usr/share/ghostscript/10.00.0/Resource/Font/NimbusSans-Bold
Loading font Helvetica-Bold (or substitute) from /usr/share/ghostscript/10.00.0/Resource/Font/NimbusSans-Bold
Loading font Helvetica-Bold (or substitute) from /usr/share/ghostscript/10.00.0/Resource/Font/NimbusSans-Bold
Loading font Helvetica-Bold (or substitute) from /usr/share/ghostscript/10.00.0/Resource/Font/NimbusSans-Bold
Page 3
Loading font Helvetica-Bold (or substitute) from /usr/share/ghostscript/10.00.0/Resource/Font/NimbusSans-Bold
Loading font Helvetica-Bold (or substitute) from /usr/share/ghostscript/10.00.0/Resource/Font/NimbusSans-Bold
Loading font Helvetica-Bold (or substitute) from /usr/share/ghostscript/10.00.0/Resource/Font/NimbusSans-Bold
Loading font Helvetica-Bold (or substitute) from /usr/share/ghostscript/10.00.0/Resource/Font/NimbusSans-Bold
Loading font Helvetica-Bold (or substitute) from /usr/share/ghostscript/10.00.0/Resource/Font/NimbusSans-Bold
Loading font Helvetica-Bold (or substitute) from /usr/share/ghostscript/10.00.0/Resource/Font/NimbusSans-Bold
Loading font Helvetica-Bold (or substitute) from /usr/share/ghostscript/10.00.0/Resource/Font/NimbusSans-Bold
Loading font Helvetica-Bold (or substitute) from /usr/share/ghostscript/10.00.0/Resource/Font/NimbusSans-Bold
Loading font Helvetica-Bold (or substitute) from /usr/share/ghostscript/10.00.0/Resource/Font/NimbusSans-Bold
Loading font Helvetica-Bold (or substitute) from /usr/share/ghostscript/10.00.0/Resource/Font/NimbusSans-Bold
Loading font Helvetica-Bold (or substitute) from /usr/share/ghostscript/10.00.0/Resource/Font/NimbusSans-Bold
Loading font Helvetica-Bold (or substitute) from /usr/share/ghostscript/10.00.0/Resource/Font/NimbusSans-Bold
Loading font Helvetica-Bold (or substitute) from /usr/share/ghostscript/10.00.0/Resource/Font/NimbusSans-Bold
...

Ghostscript 9与10的核心变化 #

• 9.x版本默认启用全局字体缓存，加载过的字体会一直保留在内存里，后续页面直接复用，不会重复加载
• 10.x版本为了降低默认内存占用，调整了缓存策略：对于使用替代字体（比如PDF里的Helvetica映射到NimbusSans）的场景，每次遇到字体请求都会触发加载检查，虽然实际可能没有重复读取磁盘，但日志输出和临时内存分配会导致性能下降，尤其是大文件
• 10.x的字体加载日志更详细，每一次字体请求都会打印加载信息，这也是日志里看起来反复加载的直接原因

恢复高效性能的方法 #

1. 用loadallfonts预加载字体 #

loadallfonts是Ghostscript的PostScript指令，能在处理PDF前把所有内置字体一次性加载到缓存，后续处理时直接调用，不会再触发加载流程。执行命令时要把指令放在PDF文件之前，格式如下：

gs -c "loadallfonts" -f -sOutputFile=page-%04d.png -dNOPAUSE -dBATCH -sDEVICE=png16m -r108 example.pdf

解释：-c用来执行PostScript代码，-f用来切换回处理输入文件的模式，必须放在PDF文件名前面。这个方法能彻底解决反复加载的问题，适合字体重复度高的大文件，但如果PDF用了很多特殊字体，预加载会占用更多内存，需要根据系统配置权衡。

2. 增大字体缓存上限 #

通过-dMaxFontCache参数设置更大的字体缓存，让Ghostscript保留已加载的字体，避免频繁释放和重新加载：

gs -dMaxFontCache=100000000 -sOutputFile=page-%04d.png -dNOPAUSE -dBATCH -sDEVICE=png16m -r108 example.pdf

数值单位是字节，这里设的是100MB，你可以根据系统内存调整大小，足够大的缓存能让Ghostscript把常用字体一直存在内存里。

3. 配置系统字体替代内置字体 #

如果PDF用的是标准字体（比如Helvetica、Times），可以让Ghostscript优先用系统安装的对应字体（比如Nimbus Sans、Liberation Fonts），减少替代字体的加载开销。编辑Ghostscript的配置文件（通常在/etc/ghostscript/10.00.0/fonts.conf），添加系统字体路径，或者直接指定字体映射规则。

关于loadallfonts的有效性 #

loadallfonts确实能解决你遇到的问题，它在初始化阶段就把所有Resource/Font目录下的字体加载到内存缓存，后续处理PDF时直接从缓存调用，不会再触发加载流程。唯一需要注意的是，如果你的PDF包含大量特殊字体，预加载会占用较多内存，需要根据自己的系统资源情况调整。

内容的提问来源于stack exchange，提问作者Lemming