feat: Hervorhebungen aus dem CSS des Buches übernehmen (P1)

Neues Modul epub2md/css.py: Es wertet die Stylesheets des Buches aus
(Typ-, Klassen- und ID-Selektoren, Nachfahre/Kind, Spezifität,
style-Attribute; @media und Pseudoklassen werden ignoriert). Daraus werden:
- fett/kursiv → **/*, unterstrichen → <u>, durchgestrichen → ~~,
  vertical-align super/sub → <sup>/<sub>
- Monospace-Einzelwörter → Inline-Code
- display:none → Element entfällt
Das gilt im Fließtext, für ganze Absätze und in HTML-Tabellen (dort als
HTML-Tags). Direkt aneinanderstoßende gleiche Hervorhebungen werden
zusammengefasst ('*x**y*' brach Markdown; Mathebuch: 305 → 249 Stellen).
Beispiele: C-Buch 799× kursiv und 648× fett, die vorher verloren gingen.
Abschaltbar mit --no-css-emphasis.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

BEDIENUNGSANLEITUNG.md

@@ -435,6 +435,7 @@ python3 epub2md_merge.py --help
 | `--code-language SPRACHE` | Sprache für Codeblöcke ohne erkannte Sprache |
 | `--keep-wrap-markers` | Druck-Umbruchzeichen `↪` im Code stehen lassen |
 | `--keep-invisible-chars` | unsichtbare Zeichen (Nullbreiten-Leerzeichen, weiche Trennstriche) behalten |
+| `--no-css-emphasis` | Hervorhebungen nur aus HTML-Tags übernehmen, nicht aus dem Stylesheet des Buches |
 | `--math auto/tex/mathml/image` | Formeldarstellung |
 | `--footnotes end-of-chapter/end-of-book/inline/keep-links` | Fußnoten-Platzierung |
 | `--format gfm/commonmark` | Markdown-Variante; `commonmark` für sehr strikte Programme |

README.md

@@ -97,6 +97,7 @@ python3 epub2md.py buch.epub output/buch --force --report berichte/buch.json
 | `--slug-language {de,en,none}` | `de` | Dateinamen: `de` ä→ae, ß→ss; `en` ä→a, ß→ss; `none` Unicode bleibt |
 | `--code-language SPRACHE` | – | Sprachlabel für Codeblöcke ohne erkannte Sprache (z. B. `python`, `c`; Aliase wie `py` erlaubt). Erkannte Labels haben Vorrang; im Bericht `detected_by: "option"` |
 | `--keep-wrap-markers` | aus | Druck-Umbruchzeichen `↪`/`➥` in Codeblöcken stehen lassen. Standard: Fortsetzungszeilen werden wieder zur ursprünglichen Codezeile zusammengefügt (Anzahl im Bericht: `wrap_lines_joined`) |
+| `--css-emphasis` / `--no-css-emphasis` | an | Fett, kursiv, unterstrichen, durchgestrichen, hoch-/tiefgestellt auch übernehmen, wenn das Buch sie nur per CSS-Klasse setzt (z. B. `span.italic`). Einzelwörter in Monospace-Schrift werden zu Inline-Code; per CSS ausgeblendete Elemente (`display:none`) entfallen. Statistik im Bericht unter `css` |
 | `--keep-invisible-chars` | aus | Nullbreiten-Zeichen und weiche Trennstriche im Fließtext behalten. Standard: entfernen, weil sie Suche und RAG stören (Anzahl im Bericht: `text_cleanup`). Code bleibt immer unverändert |
 | `--keep-html` | aus | Unbekannte/nicht sicher konvertierbare Elemente als bereinigtes HTML erhalten (sonst: Text übernommen + Eintrag in `diagnostics/unsupported-elements.md`) |
 | `--strict` | aus | Abbruch bei kritischen Fehlern (fehlende/unlesbare Spine-Dokumente, unsichere ZIP-Pfade, ungültige Spine-Verweise) |
@@ -238,6 +239,10 @@ weil CommonMark keine `[^…]`-Syntax kennt.
   (`#include`, `def …:`, Shebang, …). Ist sie unsicher, bleibt das Label leer. Bei einsprachigen
   Büchern kann `--code-language python` (o. Ä.) alle übrigen Blöcke kennzeichnen. Achtung: Das betrifft
   auch Programmausgaben und Shell-Befehle im Buch.
+- **CSS-Formatierung:** Viele Verlage setzen Hervorhebungen nur über Stylesheets. epub2md wertet die
+  CSS-Dateien des Buches aus: Klassen-, Element- und ID-Selektoren, Nachfahren- und Kind-Kombinatoren,
+  Spezifität und `style`-Attribute. `@media`-Blöcke und Selektoren mit Pseudoklassen werden ignoriert.
+  Direkt aneinanderstoßende gleiche Hervorhebungen werden zusammengefasst (`*x**y*` → `*xy*`).
 - **Gescannte Texte:** nur Bilder, kein Text (keine OCR).
 - **DRM:** wird erkannt und abgelehnt.
 - **Register:** Buchstabengruppen werden zu `##`-Überschriften, Untereinträge erhalten `– `. Interne

epub2md/cli.py

@@ -85,6 +85,9 @@ def build_parser() -> argparse.ArgumentParser:
     p.add_argument("--keep-wrap-markers", action="store_true",
                    help="Druck-Umbruchzeichen (↪/➥) in Codeblöcken nicht entfernen; Standard: fortgesetzte "
                         "Zeilen werden wieder zur ursprünglichen Codezeile zusammengefügt")
+    p.add_argument("--css-emphasis", action=argparse.BooleanOptionalAction, default=True,
+                   help="Fett/kursiv/unterstrichen/hoch-/tiefgestellt auch übernehmen, wenn das Buch sie nur per CSS "
+                        "setzt; per CSS ausgeblendete Elemente weglassen (Standard: an)")
     p.add_argument("--keep-invisible-chars", action="store_true",
                    help="Nullbreiten-Zeichen und weiche Trennstriche (U+00AD) im Fließtext behalten; Standard: entfernen "
                         "(stören Suche und Weiterverarbeitung). Code bleibt immer unverändert")
@@ -123,6 +126,7 @@ def main(argv: list[str] | None = None) -> int:
         code_language=args.code_language or "",
         keep_wrap_markers=args.keep_wrap_markers,
         keep_invisible_chars=args.keep_invisible_chars,
+        css_emphasis=args.css_emphasis,
         strict=args.strict,
         verbose=args.verbose,
         dry_run=args.dry_run,

epub2md/css.py

@@ -0,0 +1,194 @@
+"""Minimal CSS evaluation for formatting that publishers express only through stylesheets.
+
+Supports type/class/id selectors, descendant (` `) and child (`>`) combinators, specificity and source
+order, and `style` attributes. Selectors with pseudo-classes, attribute selectors or sibling combinators
+are ignored (conservative: an unknown rule never adds formatting). @-blocks (@media, @font-face, @page …)
+are skipped.
+"""
+
+from __future__ import annotations
+
+import re
+from dataclasses import dataclass
+from typing import Any
+
+from .utils import classes, local
+
+COMPOUND = re.compile(r"^(\*|[a-zA-Z][\w-]*)?((?:[.#][\w-]+)*)$")
+MONOSPACE = re.compile(r"monospace|courier|consolas|menlo|monaco|lucida console|source code|dejavu sans mono|"
+                       r"liberation mono|fira mono|fira code|inconsolata|andale mono|\bmono\b", re.I)
+
+
+@dataclass
+class _Compound:
+    tag: str | None
+    classes: frozenset[str]
+    ids: frozenset[str]
+
+    def matches(self, el: Any) -> bool:
+        if self.tag and self.tag != "*" and local(el.tag) != self.tag:
+            return False
+        if self.ids and (el.get("id") or "").lower() not in self.ids:
+            return False
+        return not self.classes or self.classes <= set(classes(el))
+
+
+@dataclass
+class _Rule:
+    parts: list[tuple[str, _Compound]]  # (combinator to the previous part, compound); first combinator is ""
+    specificity: tuple[int, int, int]
+    order: int
+    decls: dict[str, str]
+
+    def matches(self, el: Any) -> bool:
+        if not self.parts[-1][1].matches(el):
+            return False
+        node = el
+        for i in range(len(self.parts) - 1, 0, -1):
+            comb = self.parts[i][0]
+            compound = self.parts[i - 1][1]
+            node = node.getparent()
+            if comb == ">":
+                if node is None or not compound.matches(node):
+                    return False
+            else:  # descendant
+                while node is not None and not compound.matches(node):
+                    node = node.getparent()
+                if node is None:
+                    return False
+        return True
+
+
+def _parse_declarations(text: str) -> dict[str, str]:
+    decls: dict[str, str] = {}
+    for part in text.split(";"):
+        if ":" not in part:
+            continue
+        prop, value = part.split(":", 1)
+        prop = prop.strip().lower()
+        value = re.sub(r"\s*!important\s*$", "", value.strip(), flags=re.I).strip()
+        if prop and value:
+            decls[prop] = value
+    return decls
+
+
+def _parse_selector(sel: str) -> list[tuple[str, _Compound]] | None:
+    sel = sel.strip().lower()
+    if not sel or re.search(r"[:\[\]+~]", sel):
+        return None
+    tokens = re.split(r"\s*(>)\s*|\s+", sel)
+    parts: list[tuple[str, _Compound]] = []
+    comb = ""
+    for tok in tokens:
+        if tok is None or tok == "":
+            continue
+        if tok == ">":
+            comb = ">"
+            continue
+        m = COMPOUND.match(tok)
+        if not m:
+            return None
+        rest = m.group(2) or ""
+        parts.append((comb if parts else "", _Compound(
+            tag=m.group(1),
+            classes=frozenset(re.findall(r"\.([\w-]+)", rest)),
+            ids=frozenset(re.findall(r"#([\w-]+)", rest)),
+        )))
+        comb = " "
+    return parts or None
+
+
+def _strip_at_blocks(css: str) -> str:
+    """Remove @-rules including nested blocks (@media, @font-face, @supports, @page …)."""
+    out: list[str] = []
+    i = 0
+    while i < len(css):
+        if css[i] == "@":
+            brace = css.find("{", i)
+            semi = css.find(";", i)
+            if semi != -1 and (brace == -1 or semi < brace):  # @import/@charset …;
+                i = semi + 1
+                continue
+            if brace == -1:
+                break
+            depth, j = 0, brace
+            while j < len(css):
+                if css[j] == "{":
+                    depth += 1
+                elif css[j] == "}":
+                    depth -= 1
+                    if depth == 0:
+                        break
+                j += 1
+            i = j + 1
+            continue
+        out.append(css[i])
+        i += 1
+    return "".join(out)
+
+
+class StyleSheet:
+    def __init__(self, css_texts: list[str]) -> None:
+        self.rules: list[_Rule] = []
+        self._index: dict[str, list[_Rule]] = {}
+        self._cache: dict[Any, dict[str, str]] = {}
+        order = 0
+        for css in css_texts:
+            css = re.sub(r"/\*.*?\*/", "", css, flags=re.S)
+            css = _strip_at_blocks(css)
+            for selectors, body in re.findall(r"([^{}]+)\{([^{}]*)\}", css):
+                decls = _parse_declarations(body)
+                if not decls:
+                    continue
+                for sel in selectors.split(","):
+                    parts = _parse_selector(sel)
+                    if not parts:
+                        continue
+                    spec = (sum(len(c.ids) for _, c in parts), sum(len(c.classes) for _, c in parts),
+                            sum(1 for _, c in parts if c.tag and c.tag != "*"))
+                    rule = _Rule(parts, spec, order, decls)
+                    order += 1
+                    self.rules.append(rule)
+                    last = parts[-1][1]
+                    keys = [f".{c}" for c in last.classes] or ([last.tag] if last.tag and last.tag != "*" else ["*"])
+                    for key in keys[:1]:  # one index entry suffices: every key must match anyway
+                        self._index.setdefault(key, []).append(rule)
+
+    def computed(self, el: Any) -> dict[str, str]:
+        """Declared properties for ``el`` (no inheritance), including its ``style`` attribute."""
+        cached = self._cache.get(el)
+        if cached is not None:
+            return cached
+        candidates: list[_Rule] = []
+        for key in [f".{c}" for c in classes(el)] + [local(el.tag), "*"]:
+            candidates.extend(self._index.get(key, ()))
+        result: dict[str, str] = {}
+        for rule in sorted({id(r): r for r in candidates}.values(), key=lambda r: (r.specificity, r.order)):
+            if rule.matches(el):
+                result.update(rule.decls)
+        if el.get("style"):
+            result.update(_parse_declarations(el.get("style")))
+        self._cache[el] = result
+        return result
+
+
+def inline_style(el: Any) -> dict[str, str]:
+    """Only the ``style`` attribute (used when no stylesheet is available)."""
+    return _parse_declarations(el.get("style") or "")
+
+
+def emphasis(style: dict[str, str]) -> dict[str, bool]:
+    """Semantic formatting expressed by a computed style."""
+    weight = style.get("font-weight", "").lower()
+    deco = (style.get("text-decoration-line", "") + " " + style.get("text-decoration", "")).lower()
+    valign = style.get("vertical-align", "").lower()
+    return {
+        "bold": weight in ("bold", "bolder") or (weight.isdigit() and int(weight) >= 600),
+        "italic": style.get("font-style", "").lower() in ("italic", "oblique"),
+        "underline": "underline" in deco,
+        "strike": "line-through" in deco,
+        "sup": valign == "super",
+        "sub": valign == "sub",
+        "mono": bool(MONOSPACE.search(style.get("font-family", ""))),
+        "hidden": style.get("display", "").lower() == "none",
+    }

epub2md/html_converter.py

@@ -9,6 +9,7 @@ from __future__ import annotations
 
 import html
 import re
+from collections import Counter
 from collections.abc import Callable, Sequence
 from dataclasses import dataclass
 from typing import Any
@@ -17,6 +18,7 @@ from urllib.parse import unquote
 from lxml import etree
 
 from .chapters import IdCarrier, Marker, heading_level
+from .css import StyleSheet, emphasis, inline_style
 from .codeblocks import (
     code_text,
     detect_language,
@@ -95,6 +97,7 @@ class RenderOptions:
     code_language: str = ""  # --code-language: label for blocks without a detected language
     keep_wrap_markers: bool = False  # --keep-wrap-markers: do not join ↪-continued code lines
     keep_invisible_chars: bool = False  # --keep-invisible-chars: keep zero-width chars and soft hyphens
+    css_emphasis: bool = True  # --no-css-emphasis: ignore bold/italic/… that only the stylesheet expresses
 
 
 def md_escape(text: str, table: bool = False) -> str:
@@ -126,9 +129,23 @@ def escape_line_starts(text: str) -> str:
     return "\n".join(out)
 
 
+EMPH_SEP = "\x1f"  # separates open marker, content and close marker inside an ("e", …) piece
+
+
 def join_inline(pieces: list[Piece], hard_break: str = "\\\n") -> str:
     out = ""
+    last_e: tuple[int, str, str, str, int] | None = None  # (start, open, core, close, end) of the last emphasis
     for kind, s in pieces:
+        if kind == "e":
+            open_, core, close = s.split(EMPH_SEP)
+            if last_e and last_e[4] == len(out) and last_e[1] == open_ and last_e[3] == close:
+                # directly adjacent identical emphasis (<em>x</em><em>y</em>): merge, "*x**y*" would break
+                out = out[: last_e[0]]
+                core = last_e[2] + core
+            start = len(out)
+            out += open_ + core + close
+            last_e = (start, open_, core, close, len(out))
+            continue
         if kind == "t":
             s = WS.sub(" ", s)
             if not out or out.endswith((" ", "\n")):
@@ -178,6 +195,17 @@ def _collapse_blank_lines(text: str) -> str:
     return "\n".join(out)
 
 
+ITALIC_TAGS = {"em", "i", "cite", "dfn", "var"}
+BOLD_TAGS = {"strong", "b"}
+CSS_SKIP_TAGS = {"br", "wbr", "img", "svg", "image", "math", "code", "samp", "tt", "kbd", "pre"}
+
+
+def _wrap_text(text: str, marker: str) -> str:
+    """Wrap a finished paragraph in emphasis markers (whitespace stays outside)."""
+    core = text.strip()
+    return f"{marker}{core}{marker}" if core else text
+
+
 _BLOCK_SYNTAX = ("```", "~~~", "|", "<table", "- ", "> ", "#", "$$", "\\[", "* * *")
 
 
@@ -231,8 +259,12 @@ def serialize_mathml(math: Any) -> str:
 class Renderer:
     def __init__(self, options: RenderOptions, resolver: LinkResolver, media: MediaRegistry,
                  notes: NoteIndex, diag: Diagnostics, zip_names: set[str],
-                 entry_problem: Callable[[str], str | None] | None = None) -> None:
+                 entry_problem: Callable[[str], str | None] | None = None,
+                 stylesheet: StyleSheet | None = None) -> None:
         self.entry_problem = entry_problem or (lambda path: None)
+        self.css = stylesheet
+        self.css_applied: Counter[str] = Counter()
+        self.hidden_elements = 0
         self.invisible_removed = 0
         self.opt = options
         self.zip_names = zip_names
@@ -364,6 +396,8 @@ class Renderer:
 
     def block(self, el: Any) -> list[str]:
         name = local(el.tag)
+        if self._hidden(el):
+            return []
         ch = self.ch
         if ch is not None and el is ch.title_el and not heading_level(el):
             return self.heading(el, forced_level=1)
@@ -404,7 +438,24 @@ class Renderer:
             special = self._index_block(el, anchor)
             if special is not None:
                 return special
-        blocks = self.flow(el)
+        italic = bold = False
+        if self.opt.css_emphasis and local(el.tag) in ("p", "div") and not self.in_heading \
+                and not any(local(d.tag) in BLOCK_TAGS for d in iter_elements(el) if d is not el) \
+                and text_content(el).strip():
+            e = self._emphasis(el)
+            italic, bold = e["italic"] and not self.em, e["bold"] and not self.strong
+        self.em += italic
+        self.strong += bold
+        try:
+            blocks = self.flow(el)
+        finally:
+            self.em -= italic
+            self.strong -= bold
+        if (italic or bold) and len(blocks) == 1 and not _is_block_syntax(blocks[0]) and not blocks[0].startswith("<"):
+            for flag, marker, key in ((italic, "*", "italic"), (bold, "**", "bold")):
+                if flag:
+                    blocks[0] = _wrap_text(blocks[0], marker)
+                    self.css_applied[key] += 1
         if anchor:
             if blocks and not blocks[0].startswith(("#", "`", "|", "<table", "> ", "- ", "$$", "\\[", "* * *")) \
                     and not re.match(r"\d+\. ", blocks[0]):
@@ -766,7 +817,58 @@ class Renderer:
                 pieces.append(("t", self._text(child.tail)))
         return pieces
 
+    def _emphasis(self, el: Any) -> dict[str, bool]:
+        style = self.css.computed(el) if self.css is not None else inline_style(el)
+        return emphasis(style)
+
+    def _hidden(self, el: Any) -> bool:
+        """display:none in the book's CSS: readers do not show the element, so neither do we."""
+        if not self.opt.css_emphasis or not is_element(el) or not self._emphasis(el)["hidden"]:
+            return False
+        self.hidden_elements += 1
+        return True
+
     def inline(self, el: Any) -> list[Piece]:
+        """Inline rendering plus formatting that only the stylesheet expresses (P1)."""
+        name = local(el.tag)
+        if not self.opt.css_emphasis or name in CSS_SKIP_TAGS:
+            return self._inline_core(el)
+        if self._hidden(el):
+            return []
+        if self.in_heading or is_inline_code(el) or not text_content(el).strip():
+            return self._inline_core(el)
+        e = self._emphasis(el)
+        if e["mono"] and name != "a" and re.fullmatch(r"\S+", norm_ws(text_content(el))) \
+                and not any(local(d.tag) in ("img", "svg", "math", "a") for d in iter_elements(el) if d is not el):
+            self.css_applied["code"] += 1
+            anchor = self.anchors_of(el)
+            return ([("r", anchor)] if anchor else []) + [("r", inline_code(norm_ws(text_content(el))))]
+        has_link = name == "a" or any(local(d.tag) == "a" for d in iter_elements(el))
+        italic = e["italic"] and name not in ITALIC_TAGS and not self.em
+        bold = e["bold"] and name not in BOLD_TAGS and not self.strong
+        strike_marker = ("~~", "~~") if self.opt.format == "gfm" else ("<del>", "</del>")
+        wrappers = [
+            (e["sup"] and name != "sup", "<sup>", "</sup>", "sup"),
+            (e["sub"] and name != "sub", "<sub>", "</sub>", "sub"),
+            (e["underline"] and name not in ("u", "ins") and not has_link, "<u>", "</u>", "underline"),
+            (e["strike"] and name not in ("del", "s", "strike"), strike_marker[0], strike_marker[1], "strike"),
+            (italic, "*", "*", "italic"),
+            (bold, "**", "**", "bold"),
+        ]
+        self.em += italic
+        self.strong += bold
+        try:
+            pieces = self._inline_core(el)
+        finally:
+            self.em -= italic
+            self.strong -= bold
+        for flag, open_, close, key in wrappers:
+            if flag:
+                pieces = self._wrap(pieces, open_, close)
+                self.css_applied[key] += 1
+        return pieces
+
+    def _inline_core(self, el: Any) -> list[Piece]:
         name = local(el.tag)
         anchor = self.anchors_of(el) if name not in ("a",) else ""
         pre: list[Piece] = [("r", anchor)] if anchor and not self.in_heading else []
@@ -844,7 +946,7 @@ class Renderer:
             core = core[: -len(hard)].rstrip()
         if not core:
             return [("t", lead or trail)] if (lead or trail) else []
-        return [("t", lead), ("r", f"{open_}{core}{close}"), ("t", trail)]
+        return [("t", lead), ("e", f"{open_}{EMPH_SEP}{core}{EMPH_SEP}{close}"), ("t", trail)]
 
     # ------------------------------------------------------------------ links
 
@@ -1236,6 +1338,17 @@ class Renderer:
             return f"<{name}{(' ' + ' '.join(safe)) if safe else ''}>{content}</{name}>"
         if name not in HTML_KEEP_TAGS or name == "span":
             anchor = self.anchors_of(el)
+            if self.opt.css_emphasis and content.strip():
+                e = self._emphasis(el)
+                if e["hidden"]:
+                    self.hidden_elements += 1
+                    return ""
+                for flag, tag, key in ((e["italic"], "em", "italic"), (e["bold"], "strong", "bold"),
+                                       (e["underline"] and "<a " not in content, "u", "underline"),
+                                       (e["strike"], "del", "strike"), (e["sup"], "sup", "sup"), (e["sub"], "sub", "sub")):
+                    if flag:
+                        content = f"<{tag}>{content}</{tag}>"
+                        self.css_applied[key] += 1
             return anchor + content
         attrs = []
         for k, v in el.attrib.items():

epub2md/pipeline.py

@@ -16,7 +16,8 @@ from typing import Any
 from . import TOOL_NAME, __version__
 from .chapters import ChapterBuilder
 from .diagnostics import Diagnostics
-from .epub_reader import EpubReader, parse_xml
+from .css import StyleSheet
+from .epub_reader import EpubReader, decode_markup, parse_xml
 from .errors import ContainerError, InputError, StructureError
 from .footnotes import collect_notes
 from .html_converter import RenderOptions, Renderer
@@ -25,7 +26,7 @@ from .media import MediaRegistry
 from .models import Chapter
 from .normalize import Doc, book_uses_title_tables, is_html_toc_doc, make_doc, normalize_doc, remove_keep_tail
 from .references import LinkResolver
-from .utils import is_inside, iter_elements, sha256_file, slugify
+from .utils import is_inside, iter_elements, local, sha256_file, slugify, text_content
 from . import writer
 
 MARKER_FILES = ("conversion-report.json", "manifest.json")
@@ -48,6 +49,7 @@ class Options:
     code_language: str = ""
     keep_wrap_markers: bool = False
     keep_invisible_chars: bool = False
+    css_emphasis: bool = True
     strict: bool = False
     verbose: bool = False
     dry_run: bool = False
@@ -134,9 +136,10 @@ def _convert(reader: EpubReader, input_path: Path, output_dir: Path, opts: Optio
     package = reader.load_package()
     diag.step(f"EPUB {package.version}: {package.metadata.title!r}, {len(package.spine)} Spine-Dokumente")
     docs = _load_docs(reader, package, diag)
+    stylesheet = _load_stylesheet(reader, package, docs, diag)  # before normalization drops <style>
     _prepare_docs(docs, package, diag)
     notes, chapters, resolver = _build_structure(docs, package, opts, diag)
-    rendered = _render(reader, package, chapters, resolver, notes, opts, diag)
+    rendered = _render(reader, package, chapters, resolver, notes, opts, diag, stylesheet)
     files, all_chapters, report = _assemble(input_path, output_dir, opts, diag, generated_at, sha, package, docs,
                                             notes, chapters, resolver, rendered)
     if opts.dry_run:
@@ -224,8 +227,22 @@ def _build_structure(docs: list[Doc], package: Any, opts: Options,
     return notes, chapters, resolver
 
 
+def _load_stylesheet(reader: EpubReader, package: Any, docs: list[Doc], diag: Diagnostics) -> StyleSheet:
+    """All CSS of the book: manifest stylesheets (manifest order) plus <style> elements of the documents."""
+    texts: list[str] = []
+    for item in package.manifest.values():
+        if item.media_type == "text/css" or item.path.lower().endswith(".css"):
+            try:
+                texts.append(decode_markup(reader.read(item.path), item.path, diag))
+            except (KeyError, ContainerError):
+                diag.warn("css-unreadable", f"Stylesheet {item.path} nicht lesbar; seine Formatierung entfällt.", item.path)
+    for doc in docs:
+        texts.extend(text_content(e) for e in iter_elements(doc.root) if local(e.tag) == "style")
+    return StyleSheet(texts)
+
+
 def _render(reader: EpubReader, package: Any, chapters: list[Chapter], resolver: LinkResolver, notes: Any,
-            opts: Options, diag: Diagnostics) -> _Rendered:
+            opts: Options, diag: Diagnostics, stylesheet: StyleSheet | None = None) -> _Rendered:
     """Render all chapters (and the end-of-book notes file) to Markdown and register media."""
     md = package.metadata
     media = MediaRegistry(package, opts.images, opts.slug_language)
@@ -237,8 +254,8 @@ def _render(reader: EpubReader, package: Any, chapters: list[Chapter], resolver:
         RenderOptions(format=opts.format, footnotes=opts.footnotes, math=opts.math,
                       extract_media=opts.extract_media, keep_html=opts.keep_html, language=language,
                       code_language=opts.code_language, keep_wrap_markers=opts.keep_wrap_markers,
-                      keep_invisible_chars=opts.keep_invisible_chars),
+                      keep_invisible_chars=opts.keep_invisible_chars, css_emphasis=opts.css_emphasis),
-        resolver, media, notes, diag, set(reader.names), reader.entry_problem,
+        resolver, media, notes, diag, set(reader.names), reader.entry_problem, stylesheet,
     )
     width = max(3, len(str(len(chapters) + 1)))
     notes_title = "Anmerkungen" if language.startswith("de") else "Notes"
@@ -498,6 +515,8 @@ def _report(input_path: Path, sha: str, generated_at: str, package: Any, opts: O
                       "rendered": len(renderer.book_notes)},
         "special_sections": special,
         "text_cleanup": {"invisible_chars_removed": renderer.invisible_removed},
+        "css": {"rules": len(renderer.css.rules) if renderer.css else 0, "applied": dict(renderer.css_applied),
+                "hidden_elements": renderer.hidden_elements},
         "warnings": warnings,
         "errors": errors,
         "infos": [d.as_dict() for d in diag.items if d.level == "info"],

tests/test_styles.py

@@ -16,3 +16,53 @@ def test_p6_invisible_characters_removed_outside_code(convert):
     assert run.report["text_cleanup"]["invisible_chars_removed"] == 4
     kept = convert(Book(docs=[Doc("c.xhtml", body)]), "--keep-invisible-chars").chapter("001")
     assert f"Lese{SHY}rinnen" in kept
+
+
+CSS = b""".i { font-style: italic } .b { font-weight: bold } span.u { text-decoration: underline }
+.s { text-decoration: line-through } .hoch { vertical-align: super } .weg { display: none }
+li p.first > span.b { font-weight: normal; font-family: monospace } .schrift-c { font-family: "Courier New", monospace }
+p.zitat { font-style: italic } h2.t { font-weight: bold; font-style: italic } .url { text-decoration: underline }
+@media amzn-kf8 { .i { font-style: normal } }"""
+
+
+def styled(body: str, *args: str, convert=None):
+    return convert(Book(docs=[Doc("c.xhtml", body)], media={"style.css": CSS}), *args)
+
+
+def test_p1_css_classes_become_markdown_emphasis(convert):
+    body = ('<h1>K</h1><p>Ein <span class="i">kursives</span> und <span class="b">fettes</span> Wort, '
+            '<span class="u">unterstrichen</span>, <span class="s">gestrichen</span>, x<span class="hoch">2</span>, '
+            '<span class="weg">[»] </span>sichtbar, <span class="schrift-c">printf</span> und '
+            '<span class="schrift-c">zwei Wörter</span>, <span style="font-weight:700">inline</span>, '
+            '<span class="url"><a href="https://example.org">example.org</a></span>.</p>'
+            '<ul><li><p class="first"><span class="b">nicht fett im Listenkopf</span></p></li></ul>'
+            '<p class="zitat">Ein ganzer kursiver Absatz mit <em>Betonung</em>.</p>'
+            '<h2 class="t">Überschrift bleibt</h2><p><em class="i">nur einmal</em></p><pre><span class="b">code</span></pre>')
+    run = styled(body, convert=convert)
+    text = run.chapter("001")
+    assert "Ein *kursives* und **fettes** Wort, <u>unterstrichen</u>, ~~gestrichen~~, x<sup>2</sup>, sichtbar," in text
+    assert "`printf` und zwei Wörter, **inline**, [example.org](https://example.org)." in text
+    assert "[»]" not in text and "\\[»\\]" not in text
+    assert "- nicht fett im Listenkopf" in text
+    assert "*Ein ganzer kursiver Absatz mit Betonung.*" in text
+    assert "## Überschrift bleibt" in text and "*nur einmal*" in text and "**nur einmal**" not in text
+    assert "```\ncode\n```" in text
+    assert run.report["css"]["hidden_elements"] == 1
+    assert run.report["css"]["applied"]["italic"] >= 2
+    plain = styled(body, "--no-css-emphasis", convert=convert).chapter("001")
+    assert "Ein kursives und fettes Wort" in plain
+
+
+def test_p1_css_emphasis_inside_html_tables(convert):
+    body = ('<h1>T</h1><table><tr><td colspan="2"><span class="i">kursiv</span> und <span class="b">fett</span></td></tr>'
+            '<tr><td>a</td><td>b</td></tr></table>')
+    text = styled(body, convert=convert).chapter("001")
+    assert "<em>kursiv</em> und <strong>fett</strong>" in text
+
+
+def test_adjacent_emphasis_is_merged(convert):
+    body = ('<h1>K</h1><p>Fläche (A=r<sup>2</sup><span class="i">×</span><span class="i">π</span>) und '
+            '<em>x</em><em>y</em> sowie <strong>a</strong><strong>b</strong> und <em>c</em> <em>d</em>.</p>')
+    text = styled(body, convert=convert).chapter("001")
+    assert "<sup>2</sup>*×π*" in text
+    assert "*xy*" in text and "**ab**" in text and "*c* *d*" in text