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kobo-font-fix/kobofix.py

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#!/usr/bin/env python3
"""
Font processing utility for Kobo e-readers.
Processes TrueType fonts to improve compatibility with Kobo e-readers:
- Renaming fonts with a configurable prefix and updating internal metadata
(name table, CFF, post table, PS name)
- Validating and correcting PANOSE metadata based on font style
- Updating font weight metadata (OS/2 usWeightClass)
- Adjusting line spacing via font-line
- Kerning: extracting GPOS pairs (Format 1, Format 2, and Extension lookups)
into a legacy kern table, prioritized by Unicode range to fit within
format 0 size constraints
- Hinting: optionally stripping hints or applying ttfautohint
Supports --dry-run to preview what would change without modifying files.
Includes NV and KF presets for common workflows, or can be fully
configured via individual flags. Run with -h for usage details.
Requirements:
- fontTools (pip install fonttools)
- font-line (pip install font-line)
- ttfautohint (optional, for --hint additive/overwrite)
"""
import sys
import os
import shutil
import subprocess
import argparse
import logging
from pathlib import Path
from collections import defaultdict
from dataclasses import dataclass
from typing import Dict, Tuple, Optional, List
from fontTools.ttLib import TTFont, newTable
from fontTools.ttLib.tables._k_e_r_n import KernTable_format_0
# -------------
# PRESETS
# -------------
#
PRESETS = {
"nv": {
"prefix": "NV",
"line_percent": 20,
"kern": "skip",
"hint": "skip",
},
"kf": {
"prefix": "KF",
"line_percent": 0,
"kern": "add-legacy-kern",
"hint": "skip",
"remove_prefix": "NV",
},
}
# Known prefixes are automatically detected and stripped before applying
# the preset's prefix. This ensures idempotent processing.
KNOWN_PREFIXES = sorted(
{p["prefix"] for p in PRESETS.values() if "prefix" in p},
key=len, reverse=True # longest first to avoid partial matches
)
# -------------
# STYLE MAPPING
# -------------
# Style mapping for filenames and internal font data.
# If a particular style string is found in the font file name, it can be mapped.
# The values are a tuple of (human-readable_style_name, usWeightClass).
#
STYLE_MAP = {
"BoldItalic": ("Bold Italic", 700),
"Bold": ("Bold", 700),
"Italic": ("Italic", 400),
"Regular": ("Regular", 400),
}
# Configure logging for clear output
logging.basicConfig(level=logging.INFO, format='%(message)s')
logger = logging.getLogger(__name__)
@dataclass
class FontMetadata:
"""
A simple data class to hold consistent font naming and metadata.
"""
family_name: str
style_name: str
full_name: str
ps_name: str
class FontProcessor:
"""
Main font processing class.
"""
def __init__(self,
prefix: str,
line_percent: int,
):
"""
Initialize the font processor with configurable values.
If the user has not supplied custom arguments, the default values are used.
Args:
prefix: Prefix to add to font names
line_percent: Percentage for baseline adjustment
"""
self.prefix = prefix
self.line_percent = line_percent
# ============================================================
# Helper methods
# ============================================================
@staticmethod
def _get_style_from_filename(filename: str) -> Tuple[str, int]:
"""
Determine font style and weight from filename.
This function centralizes a critical piece of logic that is used in
multiple places to ensure consistency across the script.
Args:
filename: The font file name.
Returns:
A tuple of (style_name, usWeightClass).
"""
base_filename = os.path.basename(filename)
for key, (style_name, weight) in STYLE_MAP.items():
if key.lower() in base_filename.lower():
return style_name, weight
return "Regular", 400 # Default if no style found
@staticmethod
def _set_name_records(font: TTFont, name_id: int, new_name: str) -> None:
"""
Update a font's name table record for all relevant platforms,
encodings, and languages.
This method has been updated to iterate through all existing records
for the given name_id and update them, ensuring consistent naming
across different platforms like Windows and Macintosh.
"""
name_table = font["name"]
# Find all existing records for the given nameID
names_to_update = [
n for n in name_table.names if n.nameID == name_id
]
# If no records exist, add new ones for standard platforms.
if not names_to_update:
logger.debug(f" Name ID {name_id} not found; adding new records.")
try:
name_table.setName(new_name, name_id, 3, 1, 0x0409) # Windows record
name_table.setName(new_name, name_id, 1, 0, 0) # Macintosh record
logger.debug(f" Name ID {name_id} added as '{new_name}'.")
except Exception as e:
logger.warning(f" Failed to add new name ID {name_id}: {e}")
return
updated_count = 0
for name_record in names_to_update:
try:
# Determine the appropriate encoding for the platform
if name_record.platformID == 1: # Macintosh
encoded_name = new_name.encode('mac-roman', 'ignore')
if name_record.string != encoded_name:
name_record.string = encoded_name
updated_count += 1
elif name_record.platformID == 3: # Windows
encoded_name = new_name.encode('utf-16-be', 'ignore')
if name_record.string != encoded_name:
name_record.string = encoded_name
updated_count += 1
else:
# Fallback for other platforms to ensure consistency
encoded_name = new_name.encode('utf-8', 'ignore')
if name_record.string != encoded_name:
name_record.string = encoded_name
updated_count += 1
except Exception as e:
logger.warning(f" Failed to update record for Name ID {name_id} "
f"(Platform {name_record.platformID}, "
f"Encoding {name_record.platEncID}): {e}")
if updated_count > 0:
logger.debug(f" Name ID {name_id} updated for {updated_count} record(s).")
else:
logger.debug(f" Name ID {name_id} is already correct across all records.")
# ============================================================
# Metadata extraction
# ============================================================
def _get_font_metadata(
self,
font: TTFont,
font_path: str,
new_family_name: Optional[str]
) -> Optional[FontMetadata]:
"""
Extract or infer font metadata from the font and arguments.
This function acts as a single point of truth for font metadata,
ensuring consistency throughout the processing pipeline.
"""
if "name" in font:
# Determine family name from user input or best available name from font.
family_name = new_family_name if new_family_name else font["name"].getBestFamilyName()
else:
family_name = new_family_name
if not family_name:
logger.warning(" Could not determine font family name.")
return None
# Centralized logic: Determine style name from filename.
style_name, _ = self._get_style_from_filename(font_path)
# Construct the full name and PS name based on style name logic
full_name = f"{family_name}"
if style_name != "Regular":
full_name += f" {style_name}"
# If prefix is empty, don't add it to the PS name
if self.prefix:
ps_name = f"{self.prefix}_{family_name.replace(' ', '-')}"
else:
ps_name = family_name.replace(' ', '-')
if style_name != "Regular":
ps_name += f"-{style_name.replace(' ', '')}"
logger.debug(f" Constructed metadata: family='{family_name}', style='{style_name}', full='{full_name}', ps='{ps_name}'")
return FontMetadata(
family_name=family_name,
style_name=style_name,
full_name=full_name,
ps_name=ps_name
)
# ============================================================
# Kerning extraction methods
# ============================================================
@staticmethod
def _pair_value_to_kern(value1, value2) -> int:
"""
Compute a legacy kerning value from GPOS PairValue records.
This logic is specific to converting GPOS (OpenType) kerning to
the older 'kern' (TrueType) table format.
Note: Only XAdvance values are used, as they directly map to kern table semantics
(adjusting inter-character spacing). XPlacement values shift glyphs without
affecting spacing and cannot be represented in the legacy kern table. To avoid
potential issues, XPlacement values are now being ignored.
"""
kern_value = 0
if value1 is not None:
kern_value += getattr(value1, "XAdvance", 0) or 0
if value2 is not None:
kern_value += getattr(value2, "XAdvance", 0) or 0
return int(kern_value)
def _extract_format1_pairs(self, subtable) -> Dict[Tuple[str, str], int]:
"""Extract kerning pairs from PairPos Format 1 (per-glyph PairSets)."""
pairs = {}
coverage = getattr(subtable, "Coverage", None)
pair_sets = getattr(subtable, "PairSet", [])
if not coverage or not hasattr(coverage, "glyphs"):
return pairs
for idx, left_glyph in enumerate(coverage.glyphs):
if idx >= len(pair_sets):
break
for record in getattr(pair_sets[idx], "PairValueRecord", []):
right_glyph = record.SecondGlyph
kern_value = self._pair_value_to_kern(record.Value1, record.Value2)
if kern_value:
# Only set if not already present (first value wins)
key = (left_glyph, right_glyph)
if key not in pairs:
pairs[key] = kern_value
return pairs
def _extract_format2_pairs(self, subtable) -> Dict[Tuple[str, str], int]:
"""Extract kerning pairs from PairPos Format 2 (class-based)."""
pairs = {}
coverage = getattr(subtable, "Coverage", None)
class_def1 = getattr(subtable, "ClassDef1", None)
class_def2 = getattr(subtable, "ClassDef2", None)
class1_records = getattr(subtable, "Class1Record", [])
if not coverage or not hasattr(coverage, "glyphs"):
return pairs
class1_map = getattr(class_def1, "classDefs", {}) if class_def1 else {}
left_by_class = defaultdict(list)
for glyph in coverage.glyphs:
class_idx = class1_map.get(glyph, 0)
left_by_class[class_idx].append(glyph)
class2_map = getattr(class_def2, "classDefs", {}) if class_def2 else {}
right_by_class = defaultdict(list)
for glyph, class_idx in class2_map.items():
right_by_class[class_idx].append(glyph)
for class1_idx, class1_record in enumerate(class1_records):
left_glyphs = left_by_class.get(class1_idx, [])
if not left_glyphs:
continue
for class2_idx, class2_record in enumerate(class1_record.Class2Record):
right_glyphs = right_by_class.get(class2_idx, [])
if not right_glyphs:
continue
kern_value = self._pair_value_to_kern(class2_record.Value1, class2_record.Value2)
if not kern_value:
continue
for left in left_glyphs:
for right in right_glyphs:
# Only set if not already present (first value wins)
key = (left, right)
if key not in pairs:
pairs[key] = kern_value
return pairs
def extract_kern_pairs(self, font: TTFont) -> Dict[Tuple[str, str], int]:
"""
Extract kerning pairs from the font.
Prioritizes existing 'kern' table over GPOS data if present.
GPOS (Glyph Positioning) is the modern standard for kerning in OpenType fonts.
"""
pairs = {}
# If a kern table already exists, use it instead of GPOS
if "kern" in font:
kern_table = font["kern"]
for subtable in getattr(kern_table, "kernTables", []):
if hasattr(subtable, "kernTable"):
pairs.update(subtable.kernTable)
return pairs
# Otherwise, extract from GPOS
if "GPOS" in font:
gpos = font["GPOS"].table
lookup_list = getattr(gpos, "LookupList", None)
if lookup_list and lookup_list.Lookup:
for lookup in lookup_list.Lookup:
lookup_type = getattr(lookup, "LookupType", None)
subtables = getattr(lookup, "SubTable", [])
# Unwrap Extension lookups (type 9) to get the inner subtables
if lookup_type == 9:
unwrapped = []
for ext_subtable in subtables:
ext_type = getattr(ext_subtable, "ExtensionLookupType", None)
inner = getattr(ext_subtable, "ExtSubTable", None)
if ext_type == 2 and inner is not None:
unwrapped.append(inner)
subtables = unwrapped
lookup_type = 2 if unwrapped else None
if lookup_type != 2:
continue
for subtable in subtables:
fmt = getattr(subtable, "Format", None)
if fmt == 1:
extracted = self._extract_format1_pairs(subtable)
elif fmt == 2:
extracted = self._extract_format2_pairs(subtable)
else:
continue
for key, value in extracted.items():
if key not in pairs:
pairs[key] = value
return pairs
@staticmethod
def _glyph_priority(glyph_name: str, cmap_reverse: Dict[str, int]) -> int:
"""
Assign a priority to a glyph for kern pair sorting.
Lower values = higher priority. Pairs involving common glyphs
are prioritized so they fit within the subtable size limit.
"""
cp = cmap_reverse.get(glyph_name)
if cp is None:
return 4 # unmapped glyphs (ligatures, alternates, etc.)
if cp <= 0x007F:
return 0 # Basic Latin (A-Z, a-z, digits, punctuation)
if cp <= 0x00FF:
return 1 # Latin-1 Supplement (accented chars, common symbols)
if cp <= 0x024F:
return 2 # Latin Extended-A and B
return 3 # everything else
@staticmethod
def add_legacy_kern(font: TTFont, kern_pairs: Dict[Tuple[str, str], int]) -> int:
"""
Create or replace a legacy 'kern' table with the supplied pairs.
The legacy kern table format has strict size constraints:
- Most renderers (including Kobo's WebKit-based engine) only read the
first subtable, so we write exactly one.
- Format 0 subtables have a uint16 length field (max 65,535 bytes).
With a 14-byte header and 6 bytes per pair, this allows at most
(65,535 - 14) / 6 = 10,920 pairs before the length overflows.
When a font has more pairs than this (common with class-based GPOS
kerning, which can expand to 100k+ individual pairs), we prioritize
by Unicode range so the most commonly encountered pairs are kept:
- Basic Latin (U+0000-007F): English, digits, punctuation
- Latin-1 Supplement (U+0080-00FF): Western European accented chars
- Latin Extended-A/B (U+0100-024F): Central/Eastern European chars
- Everything else and unmapped glyphs (ligatures, alternates)
This means all English kerning is preserved, most Western European
kerning (French, German, Spanish, etc.) is preserved, and only less
common extended Latin pairings are dropped when truncation is needed.
"""
if not kern_pairs:
return 0
MAX_PAIRS = 10920
items = [(tuple(k), int(v)) for k, v in kern_pairs.items() if v]
if len(items) > MAX_PAIRS:
# Build reverse cmap (glyph name -> codepoint) for prioritization
cmap_reverse = {}
if "cmap" in font:
for table in font["cmap"].tables:
if hasattr(table, "cmap"):
for cp, glyph_name in table.cmap.items():
if glyph_name not in cmap_reverse:
cmap_reverse[glyph_name] = cp
# Sort by priority of both glyphs (lower = more common)
items.sort(key=lambda pair: (
FontProcessor._glyph_priority(pair[0][0], cmap_reverse) +
FontProcessor._glyph_priority(pair[0][1], cmap_reverse)
))
logger.warning(f" Kerning: {len(items)} pairs exceed the subtable limit of {MAX_PAIRS}. "
f"Keeping the {MAX_PAIRS} most common pairs.")
items = items[:MAX_PAIRS]
kern_table = newTable("kern")
kern_table.version = 0
kern_table.kernTables = []
subtable = KernTable_format_0()
subtable.version = 0
subtable.length = None
subtable.coverage = 1
subtable.kernTable = dict(items)
kern_table.kernTables.append(subtable)
# Additional subtables are not created because most renderers
# (including Kobo's WebKit-based engine) only read the first one.
font["kern"] = kern_table
return len(items)
# ============================================================
# Name table methods
# ============================================================
def rename_font(self, font: TTFont, metadata: FontMetadata) -> None:
"""
Update the font's name-related metadata.
This method uses the centralized `_set_name_records` helper to update
all relevant name fields.
"""
if "name" not in font:
logger.warning(" No 'name' table found; skipping all name changes")
return
if self.prefix:
logger.info(" Renaming the font to: " + f"{self.prefix} {metadata.full_name}")
adjusted_family_name = f"{self.prefix} {metadata.family_name}"
adjusted_full_name = f"{self.prefix} {metadata.full_name}"
else:
logger.info(" Updating font metadata (no prefix)")
adjusted_family_name = metadata.family_name
adjusted_full_name = metadata.full_name
# Update Family Name
self._set_name_records(font, 1, adjusted_family_name)
# Update Subfamily
self._set_name_records(font, 2, metadata.style_name)
# Update Full Name
self._set_name_records(font, 4, adjusted_full_name)
# Update Typographic Family
self._set_name_records(font, 16, adjusted_family_name)
# Update Preferred Subfamily
self._set_name_records(font, 17, metadata.style_name)
# Update Preferred Family
self._set_name_records(font, 18, adjusted_family_name)
# Update Unique ID (ID 3)
try:
current_unique = font["name"].getName(3, 3, 1).toUnicode()
parts = current_unique.split("Version")
version_info = f"Version{parts[1]}" if len(parts) == 2 else "Version 1.000"
if self.prefix:
new_unique_id = f"{self.prefix} {metadata.family_name.strip()}:{version_info}"
else:
new_unique_id = f"{metadata.family_name.strip()}:{version_info}"
if current_unique != new_unique_id:
self._set_name_records(font, 3, new_unique_id)
except Exception as e:
logger.warning(f" Failed to update Unique ID: {e}")
# Update PostScript Name (ID 6)
new_ps_name = metadata.ps_name
self._set_name_records(font, 6, new_ps_name)
# Update PostScript data in CFF (if applicable)
if "CFF " in font:
cff = font["CFF "].cff
cff_topdict = cff.topDictIndex[0]
if self.prefix:
cff_full_name = f"{self.prefix} {metadata.full_name}"
cff_family_name = f"{self.prefix} {metadata.family_name.replace(' ', '_')}"
else:
cff_full_name = metadata.full_name
cff_family_name = metadata.family_name.replace(' ', '_')
name_mapping = {
"FullName": cff_full_name,
"FamilyName": cff_family_name
}
for key, new_value in name_mapping.items():
if key in cff_topdict.rawDict:
current_value = cff_topdict.rawDict[key]
if current_value != new_value:
cff_topdict.rawDict[key] = new_value
logger.debug(f" CFF table '{key}' updated to '{new_value}'.")
else:
logger.debug(f" CFF table '{key}' is already correct.")
logger.warning(" CFF table found. The original font name may persist as part of an indexed `Name INDEX`. (This cannot be easily fixed with this script. If you are encountering issues, I recommend using FontForge.)")
else:
logger.debug(" No 'CFF' table in this font.")
# Update PostScript data if relevant
if "post" in font:
if hasattr(font["post"], "fontName"):
new_ps_name = metadata.ps_name
if font["post"].fontName != new_ps_name:
font["post"].fontName = new_ps_name
logger.debug(f" 'post' table updated with new fontName '{new_ps_name}'.")
else:
logger.debug(" 'post' table fontName is already correct.")
else:
logger.debug(" No 'post' table in this font.")
# ============================================================
# Weight metadata methods
# ============================================================
def update_weight_metadata(self, font: TTFont, filename: str) -> None:
"""
Update font weight metadata based on filename suffix.
This function uses the centralized style lookup, which simplifies
the logic significantly.
"""
style_name, os2_weight = self._get_style_from_filename(filename)
ps_weight = style_name.replace(" ", "")
if "OS/2" in font and hasattr(font["OS/2"], "usWeightClass"):
if font["OS/2"].usWeightClass != os2_weight:
font["OS/2"].usWeightClass = os2_weight
logger.debug(f" OS/2 usWeightClass updated to {os2_weight}.")
else:
logger.debug(" OS/2 usWeightClass is already correct.")
if "CFF " in font and hasattr(font["CFF "].cff.topDictIndex[0], "Weight"):
if getattr(font["CFF "].cff.topDictIndex[0], "Weight", "") != ps_weight:
font["CFF "].cff.topDictIndex[0].Weight = ps_weight
logger.debug(f" PostScript CFF weight updated to '{ps_weight}'.")
elif "post" in font and hasattr(font["post"], "Weight"):
if getattr(font["post"], "Weight", "") != ps_weight:
font["post"].Weight = ps_weight
logger.debug(f" PostScript 'post' weight updated to '{ps_weight}'.")
# ============================================================
# PANOSE methods
# ============================================================
def check_and_fix_panose(self, font: TTFont, filename: str) -> None:
"""
Check and adjust PANOSE values based on filename suffix.
PANOSE is an older classification system for fonts. Correcting these
values ensures better compatibility with legacy systems and font menus.
"""
style_name, _ = self._get_style_from_filename(filename)
# PANOSE expected values for each style
style_specs = {
"Bold Italic": {"weight": 8, "letterform": 3},
"Bold": {"weight": 8, "letterform": 2},
"Italic": {"weight": 5, "letterform": 3},
"Regular": {"weight": 5, "letterform": 2},
}
if "OS/2" not in font or not hasattr(font["OS/2"], "panose") or font["OS/2"].panose is None:
logger.warning(" No OS/2 table or PANOSE information found; skipping check.")
return
panose = font["OS/2"].panose
# bFamilyType 0 means "Any" — the font has no meaningful PANOSE data
if panose.bFamilyType == 0:
logger.info(" No PANOSE classification set (bFamilyType=0); skipping check.")
return
expected = style_specs.get(style_name)
if not expected:
logger.warning(f" No PANOSE specification for style '{style_name}'; skipping.")
return
changes = []
if panose.bWeight != expected["weight"]:
old_weight = panose.bWeight
panose.bWeight = expected["weight"]
changes.append(f"bWeight {old_weight}->{expected['weight']}")
if panose.bLetterForm != expected["letterform"]:
old_letterform = panose.bLetterForm
panose.bLetterForm = expected["letterform"]
changes.append(f"bLetterForm {old_letterform}->{expected['letterform']}")
if changes:
logger.info(f" PANOSE corrected: {', '.join(changes)}")
else:
logger.info(" PANOSE check passed, no modifications required.")
# ============================================================
# Hinting methods
# ============================================================
@staticmethod
def _font_has_hints(font: TTFont) -> bool:
"""Check whether a font contains TrueType hinting data."""
if "fpgm" in font or "prep" in font or "cvt " in font:
return True
if "glyf" in font:
for glyph_name in font.getGlyphOrder():
glyph = font["glyf"][glyph_name]
if hasattr(glyph, 'program') and glyph.program and glyph.program.getAssembly():
return True
return False
@staticmethod
def strip_hints(font: TTFont) -> None:
"""Remove all TrueType hints from the font."""
hints_removed = False
for table in ("fpgm", "prep", "cvt "):
if table in font:
del font[table]
hints_removed = True
if "glyf" in font:
for glyph_name in font.getGlyphOrder():
glyph = font["glyf"][glyph_name]
if hasattr(glyph, 'removeHinting'):
glyph.removeHinting()
hints_removed = True
if hints_removed:
logger.info(" Removed TrueType hints from the font.")
else:
logger.info(" No TrueType hints found to remove.")
def apply_ttfautohint(self, font_path: str) -> bool:
"""Run ttfautohint on a saved font file, replacing it in-place."""
try:
hinted_path = font_path + ".hinted"
subprocess.run(
["ttfautohint", font_path, hinted_path],
check=True, stdout=subprocess.DEVNULL, stderr=subprocess.PIPE
)
os.replace(hinted_path, font_path)
logger.info(" Applied ttfautohint.")
return True
except subprocess.CalledProcessError as e:
logger.warning(f" ttfautohint failed: {e}")
# Clean up temp file if it exists
hinted_path = font_path + ".hinted"
if os.path.exists(hinted_path):
os.remove(hinted_path)
return False
# ============================================================
# Line adjustment methods
# ============================================================
def apply_line_adjustment(self, font_path: str) -> bool:
"""
Apply font-line baseline adjustment to the font.
This external tool fixes an issue with line spacing on some e-readers.
The function handles the necessary file operations (renaming and cleanup)
after the external utility has run.
"""
try:
subprocess.run(["font-line", "percent", str(self.line_percent), font_path], check=True, stdout=subprocess.DEVNULL, stderr=subprocess.PIPE)
base, ext = os.path.splitext(font_path)
linegap_file = f"{base}-linegap{self.line_percent}{ext}"
if os.path.exists(linegap_file):
os.remove(font_path)
os.rename(linegap_file, font_path)
logger.info(f" Line spacing adjusted ({self.line_percent}% baseline shift).")
return True
else:
logger.warning(f" Expected font-line output '{linegap_file}' not found.")
return False
except subprocess.CalledProcessError as e:
logger.warning(f" font-line failed: {e}")
return False
except Exception as e:
logger.warning(f" Unexpected error during line adjustment: {e}")
return False
# ============================================================
# Main processing method
# ============================================================
def _resolve_family_name(self, font: TTFont, new_name: Optional[str], remove_prefix: Optional[str]) -> Optional[str]:
"""
Determine the effective family name for the font.
Strips known prefixes (from presets) automatically, then applies
--remove-prefix and --name overrides.
"""
if new_name is not None:
return new_name
current_family_name = font["name"].getBestFamilyName()
if not current_family_name:
return None
# Auto-strip known prefixes (NV, KF, etc.)
family_name = current_family_name
for known in KNOWN_PREFIXES:
if family_name.startswith(known + " "):
family_name = family_name[len(known + " "):]
break
# Also handle --remove-prefix for custom prefixes
if remove_prefix and current_family_name.startswith(remove_prefix + " "):
family_name = current_family_name[len(remove_prefix + " "):]
# Return None if nothing changed (let _get_font_metadata use the stripped name)
return family_name if family_name != current_family_name else None
def _analyze_changes(self,
font: TTFont,
font_path: str,
kern_mode: str,
hint_mode: str,
metadata: FontMetadata,
) -> List[str]:
"""
Analyze what changes would be made to the font.
Returns a list of human-readable change descriptions.
This is the single source of truth for both dry-run and processing.
"""
changes = []
# Check WWS names
if font["name"]:
has_wws = any(n.nameID in (21, 22) for n in font["name"].names)
if has_wws:
changes.append("Remove WWS Family/Subfamily names (ID 21, 22)")
# Check rename
if self.prefix:
target_full = f"{self.prefix} {metadata.full_name}"
else:
target_full = metadata.full_name
current_full = font["name"].getBestFullName() if "name" in font else None
if current_full != target_full:
changes.append(f"Rename font to '{target_full}'")
# Check PANOSE
style_name, _ = self._get_style_from_filename(font_path)
style_specs = {
"Bold Italic": {"weight": 8, "letterform": 3},
"Bold": {"weight": 8, "letterform": 2},
"Italic": {"weight": 5, "letterform": 3},
"Regular": {"weight": 5, "letterform": 2},
}
if "OS/2" in font and hasattr(font["OS/2"], "panose") and font["OS/2"].panose:
panose = font["OS/2"].panose
# Skip fonts with no meaningful PANOSE data (bFamilyType 0 = "Any")
if panose.bFamilyType != 0:
expected = style_specs.get(style_name, {})
if expected:
if panose.bWeight != expected["weight"]:
changes.append(f"Fix PANOSE bWeight: {panose.bWeight} -> {expected['weight']}")
if panose.bLetterForm != expected["letterform"]:
changes.append(f"Fix PANOSE bLetterForm: {panose.bLetterForm} -> {expected['letterform']}")
# Check weight metadata
_, os2_weight = self._get_style_from_filename(font_path)
if "OS/2" in font and hasattr(font["OS/2"], "usWeightClass"):
if font["OS/2"].usWeightClass != os2_weight:
changes.append(f"Update usWeightClass: {font['OS/2'].usWeightClass} -> {os2_weight}")
# Check kerning
# Note: As of firmware 4.45, Kobo reads GPOS kerning data correctly,
# but only when webkitTextRendering=optimizeLegibility is enabled.
# Since this setting is disabled by default, a legacy kern table is
# still needed for most users.
if kern_mode in ("add-legacy-kern", "legacy-kern-only"):
has_kern = "kern" in font
has_gpos = "GPOS" in font
new_pairs = self.extract_kern_pairs(font)
if new_pairs:
new_items = [(tuple(k), int(v)) for k, v in new_pairs.items() if v]
if len(new_items) > 10920:
cmap_reverse = {}
if "cmap" in font:
for table in font["cmap"].tables:
if hasattr(table, "cmap"):
for cp, glyph_name in table.cmap.items():
if glyph_name not in cmap_reverse:
cmap_reverse[glyph_name] = cp
new_items.sort(key=lambda pair: (
self._glyph_priority(pair[0][0], cmap_reverse) +
self._glyph_priority(pair[0][1], cmap_reverse)
))
total = len(new_items)
new_items = new_items[:10920]
else:
total = len(new_items)
new_table = dict(new_items)
if has_kern:
existing_pairs = {}
for st in font["kern"].kernTables:
if hasattr(st, "kernTable"):
existing_pairs.update(st.kernTable)
if existing_pairs != new_table:
changes.append(f"Update kern table ({len(new_table)} pairs)")
else:
changes.append(f"Create legacy kern table from GPOS ({len(new_table)} pairs)")
if total > 10920:
changes.append(f" Truncate from {total} to 10920 pairs (format 0 limit)")
else:
if not has_kern and has_gpos:
changes.append("GPOS table found but contained no kern pairs")
elif not has_kern:
changes.append("No kerning data found (no GPOS or kern table)")
if kern_mode == "legacy-kern-only" and has_gpos:
changes.append("Remove GPOS table")
# Check hinting
if hint_mode == "strip":
if self._font_has_hints(font):
changes.append("Strip TrueType hints")
elif hint_mode == "overwrite":
changes.append("Apply ttfautohint (overwrite)")
elif hint_mode == "additive":
if not self._font_has_hints(font):
changes.append("Apply ttfautohint (additive)")
# Check line adjustment
if self.line_percent != 0:
if "OS/2" in font and "head" in font:
upm = font["head"].unitsPerEm
asc = font["OS/2"].sTypoAscender
desc = font["OS/2"].sTypoDescender
gap = font["OS/2"].sTypoLineGap
current_pct = round(((asc - desc + gap) / upm - 1) * 100)
if current_pct != self.line_percent:
changes.append(f"Adjust line spacing ({self.line_percent}% baseline shift, currently {current_pct}%)")
else:
changes.append(f"Adjust line spacing ({self.line_percent}% baseline shift)")
# Check output path
output_path = self._generate_output_path(font_path, metadata)
if output_path != font_path:
changes.append(f"Save as: {output_path}")
return changes
def process_font(self,
kern_mode: str,
font_path: str,
new_name: Optional[str] = None,
remove_prefix: Optional[str] = None,
hint_mode: str = "skip",
dry_run: bool = False,
) -> bool:
"""
Process a single font file, or report what would change in dry-run mode.
"""
label = "Dry run" if dry_run else "Processing"
logger.info(f"\n{label}: {font_path}")
try:
font = TTFont(font_path)
except Exception as e:
logger.error(f" Failed to open font: {e}")
return False
effective_name = self._resolve_family_name(font, new_name, remove_prefix)
metadata = self._get_font_metadata(font, font_path, effective_name)
if not metadata:
return False
changes = self._analyze_changes(font, font_path, kern_mode, hint_mode, metadata)
if not changes:
logger.info(" No changes needed.")
return True
# Report changes
for change in changes:
logger.info(f" {change}")
if dry_run:
return True
# Apply changes
try:
# Remove WWS names
if font["name"]:
old_names_list = font["name"].names
new_names_list = [n for n in old_names_list if n.nameID not in (21, 22)]
font["name"].names = new_names_list
self.rename_font(font, metadata)
self.check_and_fix_panose(font, font_path)
self.update_weight_metadata(font, font_path)
if kern_mode in ("add-legacy-kern", "legacy-kern-only"):
kern_pairs = self.extract_kern_pairs(font)
if kern_pairs:
self.add_legacy_kern(font, kern_pairs)
if kern_mode == "legacy-kern-only" and "GPOS" in font:
del font["GPOS"]
if hint_mode == "strip":
self.strip_hints(font)
output_path = self._generate_output_path(font_path, metadata)
font.save(output_path)
logger.info(f" Saved: {output_path}")
if hint_mode == "overwrite":
self.apply_ttfautohint(output_path)
elif hint_mode == "additive" and not self._font_has_hints(font):
self.apply_ttfautohint(output_path)
if self.line_percent != 0:
# Check if line spacing already matches target
needs_adjustment = True
if "OS/2" in font and "head" in font:
upm = font["head"].unitsPerEm
asc = font["OS/2"].sTypoAscender
desc = font["OS/2"].sTypoDescender
gap = font["OS/2"].sTypoLineGap
current_pct = round(((asc - desc + gap) / upm - 1) * 100)
needs_adjustment = current_pct != self.line_percent
if needs_adjustment:
self.apply_line_adjustment(output_path)
return True
except Exception as e:
logger.error(f" Processing failed: {e}")
return False
def _generate_output_path(self, original_path: str, metadata: FontMetadata) -> str:
"""
Generate the output path for the processed font.
This function now uses the centralized `STYLE_MAP` to ensure filename
suffixes are consistent with the styles found in the font's internal metadata.
"""
dirname = os.path.dirname(original_path)
original_name, ext = os.path.splitext(os.path.basename(original_path))
style_suffix = ""
for key in STYLE_MAP:
if key.lower() in original_name.lower():
style_suffix = key
break
style_part = f"-{style_suffix}" if style_suffix else ""
if self.prefix:
base_name = f"{self.prefix}_{metadata.family_name.replace(' ', '_')}{style_part}"
else:
base_name = f"{metadata.family_name.replace(' ', '_')}{style_part}"
return os.path.join(dirname, f"{base_name}{ext.lower()}")
def check_dependencies(hint_mode: str, line_percent: int) -> None:
"""Check that all required external tools are available before processing."""
missing = []
if hint_mode in ("additive", "overwrite"):
if shutil.which("ttfautohint") is None:
missing.append("ttfautohint")
if line_percent != 0:
if shutil.which("font-line") is None:
missing.append("font-line")
if missing:
logger.error(f"Missing required dependencies: {', '.join(missing)}")
logger.error("Please install them before running this script.")
sys.exit(1)
def validate_font_files(font_paths: List[str]) -> Tuple[List[str], List[str]]:
"""Validate font files for processing."""
valid_files = []
invalid_files = []
for path in font_paths:
if not os.path.isfile(path):
logger.warning(f"File not found: {path}")
continue
if not path.lower().endswith(".ttf"):
logger.error(f"Unsupported file type: {path} (only .ttf files are supported)")
invalid_files.append(os.path.basename(path))
continue
has_valid_suffix = any(
key.lower() in os.path.basename(path).lower() for key in STYLE_MAP
)
if has_valid_suffix:
valid_files.append(path)
else:
invalid_files.append(os.path.basename(path))
return valid_files, invalid_files
def main():
"""Main entry point."""
preset_names = ", ".join(PRESETS.keys())
parser = argparse.ArgumentParser(
description="Process fonts for Kobo e-readers: add prefix, kern table, "
"PANOSE validation, and line adjustments.",
formatter_class=argparse.RawDescriptionHelpFormatter,
epilog=f"""
Presets:
nv Prepare fonts for the ebook-fonts repository. Applies NV prefix,
20%% line spacing. Does not modify kerning or hinting.
kf Prepare KF fonts from NV fonts. Applies KF prefix, replaces NV
prefix, adds legacy kern table. No line spacing changes.
Examples:
Using a preset:
%(prog)s --preset nv *.ttf
%(prog)s --preset kf *.ttf
Custom processing:
%(prog)s --prefix KF --name="Fonty" --line-percent 20 --kern add-legacy-kern *.ttf
If no preset or flags are provided, you will be prompted to choose a preset.
"""
)
parser.add_argument("fonts", nargs="+",
help="Font files to process (*.ttf). You can use a wildcard (glob).")
parser.add_argument("--preset", type=str, choices=PRESETS.keys(),
help=f"Use a preset configuration ({preset_names}).")
parser.add_argument("--name", type=str,
help="Optional new family name for all fonts. Other font metadata like copyright info is unaffected.")
parser.add_argument("--prefix", type=str,
help="Prefix to add to font names. Set to empty string to omit prefix.")
parser.add_argument("--line-percent", type=int,
help="Line spacing adjustment percentage. Set to 0 to make no changes to line spacing.")
parser.add_argument("--kern", type=str,
choices=["add-legacy-kern", "legacy-kern-only", "skip"],
help="Kerning mode: 'add-legacy-kern' extracts GPOS pairs into a legacy kern table, "
"'legacy-kern-only' does the same but removes the GPOS table afterwards, "
"'skip' leaves kerning untouched.")
parser.add_argument("--dry-run", action="store_true",
help="Report what would change without modifying any files.")
parser.add_argument("--verbose", action="store_true",
help="Enable verbose output.")
parser.add_argument("--remove-prefix", type=str,
help="Remove a leading prefix from font names before applying the new prefix. Only works if `--name` is not used. (e.g., --remove-prefix=\"NV\")")
parser.add_argument("--hint", type=str,
choices=["skip", "additive", "overwrite", "strip"],
help="Hinting mode: 'skip' does nothing, 'additive' runs ttfautohint on fonts lacking hints, "
"'overwrite' runs ttfautohint on all fonts, 'strip' removes all TrueType hints.")
args = parser.parse_args()
if args.verbose:
logging.getLogger().setLevel(logging.DEBUG)
# Determine which flags were explicitly set by the user
manual_flags = {k for k in ("prefix", "line_percent", "kern", "hint", "remove_prefix", "name")
if getattr(args, k) is not None}
# If no preset and no manual flags, prompt the user to choose a preset
if args.preset is None and not manual_flags:
logger.info("No preset or flags specified. Available presets:")
for name, values in PRESETS.items():
logger.info(f" {name}")
choice = input("\nChoose a preset: ").strip().lower()
if choice not in PRESETS:
logger.error(f"Unknown preset '{choice}'. Available: {preset_names}")
sys.exit(1)
args.preset = choice
# Apply preset values as defaults, then let explicit flags override
if args.preset:
preset = PRESETS[args.preset]
for key, value in preset.items():
if key not in manual_flags:
setattr(args, key, value)
# Fill in remaining defaults for any unset flags
if args.prefix is None:
parser.error("--prefix is required when not using a preset.")
if args.line_percent is None:
parser.error("--line-percent is required when not using a preset.")
if args.kern is None:
args.kern = "skip"
if args.hint is None:
args.hint = "skip"
if args.name and args.remove_prefix:
parser.error("--name and --remove-prefix cannot be used together. Use --name to set the font name directly, or --remove-prefix to strip an existing prefix.")
if not args.dry_run:
check_dependencies(args.hint, args.line_percent)
valid_files, invalid_files = validate_font_files(args.fonts)
if invalid_files:
logger.error("\nERROR: The following fonts have invalid filenames:")
logger.error(f"(Must contain one of the following: {', '.join(STYLE_MAP.keys())})")
for filename in invalid_files:
logger.error(f" {filename}")
if not valid_files:
sys.exit(1)
response = input("\nContinue with valid files only? [y/N]: ")
if response.lower() != 'y':
sys.exit(1)
if not valid_files:
logger.error("No valid font files to process.")
sys.exit(1)
processor = FontProcessor(
prefix=args.prefix,
line_percent=args.line_percent,
)
success_count = 0
for font_path in valid_files:
if processor.process_font(
args.kern,
font_path,
args.name,
args.remove_prefix,
args.hint,
args.dry_run,
):
success_count += 1
logger.info(f"\n{'='*50}")
if args.dry_run:
logger.info(f"Checked {success_count}/{len(valid_files)} fonts.")
else:
logger.info(f"Processed {success_count}/{len(valid_files)} fonts successfully.")
if success_count < len(valid_files):
sys.exit(1)
if __name__ == "__main__":
main()
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