FreeType字形指标缓存多个字体大小 [英] FreeType Glyph Metrics Caching of multiple Font sizes

问题描述

我有一个项目，可以将产品信息呈现到给定的模板(自定义XML格式)上，然后以自定义二进制LCD格式进行呈现并将其转换(简化的步骤)

I have a project that renders product information onto a given template (custom XML format), then renders and converts it in a custom binary LCD format (steps simplified)

我们的客户现在需要自动调整文字容器. (客户提供了一个特定大小的框，并且各种字符串必须自动调整大小以适合该容器

Our customers now want auto-fitting text container. (customer gives a box of specific size and all kinds of strings have to get auto-resized to fit into that container

为此，我必须计算多种字体大小(例如100pt不适合，99pt不适合，98pt不适合...，...，65pt适合)的字符串宽度(自由类型:每个字符/字形)！ )

For that I have to calculate the width of the string (freetype: each char/glyph) for multiple font-sizes (e.g. 100pt doesnt fit, 99pt doesnt fit, 98pt doesnt..., ..., 65pt fits!)

问题在于，每个自动适配元素的freetype需要花费大量时间(〜20-30 ms)，而整个应用程序只能使用〜100ms的时间. (因此，当客户再添加5个自动调整元素时，已经保证超过100毫秒)

The Problem is that freetype takes a lot of time (~20-30 ms) for each auto-fit element and I have only ~100ms for my whole application to use. (so when customer adds 5 more autofit elements it's already guaranteed to exceed ~100 ms)

一个自制的字体缓存生成器，它获取字体文件并计算从1pt到100pt的字体大小的每个unicode字符的宽度.然后它从这样的数据中生成C源代码:

A selfmade font-cache-generator which takes a font-file and calculates the widths of each unicode-character for font-sizes from 1pt to 100pt. Then it generates C source code out of the data like this:

//
#define  COUNT_SIZES  100    // Font-Size 1-100
#define  COUNT_CHARS  65536  // Full Unicode Table
int char_sizes[COUNT_SIZES][COUNT_CHARS] = 
{
   {1,1,2,2,3,1,1,2,2,3,1,2,2,1,2,2,3,1,2,.......// 65536
   {2,2,3,3,4,2,1,3,3,4,2,3,3,2,3,3,4,2,3,.......// 65536
   {2,3,4,3,5,2,2,4,4,5,2,4,4,2,4,3,5,3,3,.......// 65536
   // ...
   // 100 font sizes
};

在动态库(.so)中编译的文件大小为25 MB，"dlload"大约需要50ms，"dlsym"大约需要10ms(WAAAAAAY太多！)

That compiled in a dynamic lib (.so) is 25 MB in size and takes ~50ms to "dlload" and ~10ms to "dlsym" (WAAAAAAY too much!)

以同样的方式，但是只有ASCII表(因此65536中只有128个)可以编译成58 KB的.so文件，"dlload"大约需要500µs，"dlsym"大约需要100µs(非常好！)

The same way but only ASCII table (so only 128 of 65536) compiles into a 58 KB .so file and takes ~500µs for "dlload" and ~100µs for "dlsym" (very nice!)

我的下一个尝试是将font-cache-generator集成到我的项目中，并且仅缓存特定客户所需的字形(欧洲的客户需要约500个字形，亚洲的一个(例如繁体中文)则需要2500个字形) (仅是示例，不确定，甚至可能还需要)

My next attempt would be to integrate the font-cache-generator into my project and cache only the glyphs I need for the specific customer (customer in europe needs ~500 glyphs, one in asia (e.g. traditional chinese) needs ~2500 (only examples, not exactly sure, maybe even more needed)

但是在我进行艰苦的旅程(:()之前，我想问你是否知道一种更好的方法?一个图书馆/项目可以做到这一点?

But before I take on that hard-work journey (:() I wanted to ask you if you know a better way of doing it? A library/project that does just that?

我不敢相信这是不可能的，否则浏览器如何显示lorem ipsum而不加载秒数? :D

I cannot believe that it's not possible, how should a browser show lorem ipsum without loading seconds otherwise? :D

关于如何解决此性能问题的任何想法?

Any idea on how to solve this performance issue?

关于数据缓存的任何信息性链接都可以极快地访问缓存(大约< 1ms)?

Any informative link on data caching with extremly fast access to cache (somewhat <1ms)?

• Unix (Ubuntu 16.04) 64位
• x86 AND arm 体系结构存在！

• Unix (Ubuntu 16.04) 64bit
• x86 AND arm architectures exist!

推荐答案

我发现了使用这些库的一种可能方法:

I found one possible way using these libraries:

• ICU (用于unicode)
• 自由类型(用于字形)
• Harfbuzz (用于布局)

• ICU (for unicode)
• Freetype (for the Glyphs)
• Harfbuzz (for layout)

Github项目: Harfbuzz-ICU-Freetype

Github Project: Harfbuzz-ICU-Freetype

宽松的构建说明:

• CMakeLists.txt option(WITH_XX "DESCRIPT." ON/OFF)
中的搜索选项
• 使用-D启用CMake选项:cmake -DWITH_ZLIB=ON -DWITH_Harfbuzz=ON ..
• mkdir build && cd build && cmake [option [option [...]]] ..
• make -j $count_of_cpu_cores && sudo make install

• Search options in CMakeLists.txt option(WITH_XX "DESCRIPT." ON/OFF)
• Enable CMake options with -D: cmake -DWITH_ZLIB=ON -DWITH_Harfbuzz=ON ..
• mkdir build && cd build && cmake [option [option [...]]] ..
• make -j $count_of_cpu_cores && sudo make install

Google上的一些 Harfbuzz布局教程/指南

Google for some Harfbuzz Layout tutorials / guides

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