xref: /aosp_15_r20/external/fonttools/Snippets/compact_gpos.py (revision e1fe3e4ad2793916b15cccdc4a7da52a7e1dd0e9) 
1#! /usr/bin/env python3
2
3"""
4Sample script to use the otlLib.optimize.gpos functions to compact GPOS tables
5of existing fonts. This script takes one or more TTF files as arguments and
6will create compacted copies of the fonts using all available modes of the GPOS
7compaction algorithm. For each copy, it will measure the new size of the GPOS
8table and also the new size of the font in WOFF2 format. All results will be
9printed to stdout in CSV format, so the savings provided by the algorithm in
10each mode can be inspected.
11
12This was initially made to debug the algorithm but can also be used to choose
13a mode value for a specific font (trade-off between bytes saved in TTF format
14vs more bytes in WOFF2 format and more subtables).
15
16Run:
17
18python Snippets/compact_gpos.py MyFont.ttf > results.csv
19"""
20
21import argparse
22from collections import defaultdict
23import csv
24import time
25import sys
26from pathlib import Path
27from typing import Any, Iterable, List, Optional, Sequence, Tuple
28
29from fontTools.ttLib import TTFont
30from fontTools.otlLib.optimize import compact
31
32MODES = [str(c) for c in range(1, 10)]
33
34
35def main(args: Optional[List[str]] = None):
36    parser = argparse.ArgumentParser()
37    parser.add_argument("fonts", type=Path, nargs="+", help="Path to TTFs.")
38    parsed_args = parser.parse_args(args)
39
40    runtimes = defaultdict(list)
41    rows = []
42    font_path: Path
43    for font_path in parsed_args.fonts:
44        font = TTFont(font_path)
45        if "GPOS" not in font:
46            print(f"No GPOS in {font_path.name}, skipping.", file=sys.stderr)
47            continue
48        size_orig = len(font.getTableData("GPOS")) / 1024
49        print(f"Measuring {font_path.name}...", file=sys.stderr)
50
51        fonts = {}
52        font_paths = {}
53        sizes = {}
54        for mode in MODES:
55            print(f"    Running mode={mode}", file=sys.stderr)
56            fonts[mode] = TTFont(font_path)
57            before = time.perf_counter()
58            compact(fonts[mode], mode=str(mode))
59            runtimes[mode].append(time.perf_counter() - before)
60            font_paths[mode] = (
61                font_path.parent
62                / "compact"
63                / (font_path.stem + f"_{mode}" + font_path.suffix)
64            )
65            font_paths[mode].parent.mkdir(parents=True, exist_ok=True)
66            fonts[mode].save(font_paths[mode])
67            fonts[mode] = TTFont(font_paths[mode])
68            sizes[mode] = len(fonts[mode].getTableData("GPOS")) / 1024
69
70        print(f"    Runtimes:", file=sys.stderr)
71        for mode, times in runtimes.items():
72            print(
73                f"        {mode:10} {' '.join(f'{t:5.2f}' for t in times)}",
74                file=sys.stderr,
75            )
76
77        # Bonus: measure WOFF2 file sizes.
78        print(f"    Measuring WOFF2 sizes", file=sys.stderr)
79        size_woff_orig = woff_size(font, font_path) / 1024
80        sizes_woff = {
81            mode: woff_size(fonts[mode], font_paths[mode]) / 1024 for mode in MODES
82        }
83
84        rows.append(
85            (
86                font_path.name,
87                size_orig,
88                size_woff_orig,
89                *flatten(
90                    (
91                        sizes[mode],
92                        pct(sizes[mode], size_orig),
93                        sizes_woff[mode],
94                        pct(sizes_woff[mode], size_woff_orig),
95                    )
96                    for mode in MODES
97                ),
98            )
99        )
100
101    write_csv(rows)
102
103
104def woff_size(font: TTFont, path: Path) -> int:
105    font.flavor = "woff2"
106    woff_path = path.with_suffix(".woff2")
107    font.save(woff_path)
108    return woff_path.stat().st_size
109
110
111def write_csv(rows: List[Tuple[Any]]) -> None:
112    sys.stdout.reconfigure(encoding="utf-8")
113    sys.stdout.write("\uFEFF")
114    writer = csv.writer(sys.stdout, lineterminator="\n")
115    writer.writerow(
116        [
117            "File",
118            "Original GPOS Size",
119            "Original WOFF2 Size",
120            *flatten(
121                (
122                    f"mode={mode}",
123                    f"Change {mode}",
124                    f"mode={mode} WOFF2 Size",
125                    f"Change {mode} WOFF2 Size",
126                )
127                for mode in MODES
128            ),
129        ]
130    )
131    for row in rows:
132        writer.writerow(row)
133
134
135def pct(new: float, old: float) -> float:
136    return -(1 - (new / old))
137
138
139def flatten(seq_seq: Iterable[Iterable[Any]]) -> List[Any]:
140    return [thing for seq in seq_seq for thing in seq]
141
142
143if __name__ == "__main__":
144    main()
145