xyou
f1a2a110d7
Add the current OS source tree, build scripts, system image layout, and development notes covering DMA page allocation, e1000 bring-up, net API dispatch, and DHCP work in progress.
69 lines
1.9 KiB
Plaintext
69 lines
1.9 KiB
Plaintext
# Deshab Bitmap Font (.dbf)
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`CODE/font` 包含 Deshab 自研位图字体工具和规范。
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## 文件格式
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```text
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Offset Size Field
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0 4 magic "DBF\x10" (version 16)
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4 4 u32 glyph_count
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8 2 u16 default_width
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10 2 u16 default_height
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12 2 u16 bits_per_pixel (8=grayscale)
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14 N×12 index table (N entries)
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... ... glyph bitmap data
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```
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每条索引：
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```text
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[0..1] u16 codepoint (Unicode BMP)
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[2..3] u16 actual_width (pixels)
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[4..7] u32 data_offset
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[8..11] u32 data_size
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```
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索引按 codepoint 升序排列，可用二分查找。
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## 字体文件
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| 文件 | 大小 | 字形数 | 精度 |
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|------|------|--------|------|
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| [simhei_16.dbf](file:///d:/Code/Deshab/SYSTEM/system/font/simhei_16.dbf) | 1.8MB | 6858 | 16×16 8bpp |
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| [simhei_24.dbf](file:///d:/Code/Deshab/SYSTEM/system/font/simhei_24.dbf) | 3.9MB | 6858 | 24×24 8bpp |
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| [simhei_32.dbf](file:///d:/Code/Deshab/SYSTEM/system/font/simhei_32.dbf) | 6.9MB | 6858 | 32×32 8bpp |
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字形覆盖：GB2312 全部 6763 个简体汉字 + ASCII 32–126 可打印字符。
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## 生成工具
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```bash
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python CODE/font/mkfont.py <ttf_path> <pixel_size> <output.dbf>
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```
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依赖：Python 3 + Pillow (`pip install Pillow`)
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## C 头文件
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[dbf.h](file:///d:/Code/Deshab/CODE/font/dbf.h) 定义数据结构和二分查找函数：
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```c
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#include "dbf.h"
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const u8 *font = ...; // 加载 .dbf 到内存
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dbf_header *hdr = (dbf_header *)font;
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dbf_index_entry *idx = (dbf_index_entry *)(font + 14);
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int entry = dbf_lookup(idx, hdr->count, codepoint);
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if (entry >= 0) {
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u8 *glyph = font + idx[entry].offset;
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u16 w = idx[entry].width;
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u16 h = hdr->height;
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// 逐行渲染 8bpp 灰度位图
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}
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```
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## 使用方式
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1. 启动时将 `.dbf` 文件通过 boot module 或 FAT32 加载到内存
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2. GBK/GB2312 双字节序列转为 Unicode codepoint 后查表
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3. 8bpp 灰度可直接 alpha-blend 到 framebuffer
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