feat(transit): 支持Markdown图片转Word图片段落

- 新增 transit/images.py 模块处理图片解析和插入逻辑
- 实现 `<img>` 标签解析为独立图片段落
- 添加图片尺寸检测和自适应缩放功能（超出页面宽度时自动缩放）
- 支持图标题居中显示和图片居中对齐
- 优化 body_to_paragraphs 函数，添加图片处理逻辑
- 更新 README.md 使用说明，添加模板文件要求说明

BREAKING CHANGE: 图片处理方式变更，需要包含 sample.docx 模板文件

README.md

@@ -1,4 +1,5 @@
 使用方法
 ```shell
-py .\test.py .\毕业论文初稿.md
+# 需要 sample.docx 文件 且 该文件有 {{xxx}} 模板引擎的内容
+python .\test.py .\毕业论文初稿.md
 ```

transit/body.py

@@ -7,9 +7,12 @@ Markdown 正文 → Word 段落转换。
 
 import re
 from copy import deepcopy
+
 from docx import Document
 from docx.oxml.ns import qn
 
+from .images import make_image_paragraph, is_figure_caption, insert_image_paragraphs
+
 _PAT_HEADING = re.compile(r"^(#{1,6})\s+(.+)$", re.MULTILINE)
 
 
@@ -33,17 +36,28 @@ def body_to_paragraphs(
     paragraphs: list[dict] = []
     last_end = 0
 
+    def _add_block(block: str) -> None:
+        block = block.strip()
+        if not block:
+            return
+        # 图片段落
+        img = make_image_paragraph(block)
+        if img:
+            paragraphs.append(img)
+            return
+        # 跳过紧跟在图片后的重复图标题
+        if paragraphs and paragraphs[-1].get("type") == "image" and is_figure_caption(block):
+            return
+        # 普通正文段落
+        paragraphs.append({"text": block, "level": 0, "style": body_style})
+
     for m in _PAT_HEADING.finditer(md_text):
         # 标题前的普通文本
         if m.start() > last_end:
             pre = md_text[last_end : m.start()].strip()
             if pre:
                 for block in re.split(r"\n\s*\n", pre):
-                    block = block.strip()
-                    if block:
-                        paragraphs.append(
-                            {"text": block, "level": 0, "style": body_style}
-                        )
+                    _add_block(block)
 
         level = len(m.group(1)) + level_offset
         heading_text = m.group(2).strip()
@@ -56,11 +70,7 @@ def body_to_paragraphs(
     tail = md_text[last_end:].strip()
     if tail:
         for block in re.split(r"\n\s*\n", tail):
-            block = block.strip()
-            if block:
-                paragraphs.append(
-                    {"text": block, "level": 0, "style": body_style}
-                )
+            _add_block(block)
 
     return paragraphs
 
@@ -94,31 +104,36 @@ def replace_placeholder(
             parent.remove(para._element)
 
             for pd_data in reversed(paragraphs):
-                new_p = doc.add_paragraph(pd_data["text"])
-                style_name = pd_data["style"]
+                if pd_data.get("type") == "image":
+                    insert_image_paragraphs(
+                        doc, [pd_data], idx=idx, parent=parent
+                    )
+                else:
+                    new_p = doc.add_paragraph(pd_data["text"])
+                    style_name = pd_data["style"]
 
-                # 尝试应用样式，逐步降级
-                applied = _apply_style(new_p, doc, style_name)
-                if not applied and style_name.startswith("Heading"):
-                    new_p.style = doc.styles["Normal"]
-                elif not applied:
-                    if placeholder_style:
-                        _apply_style(new_p, doc, placeholder_style)
-                    if new_p.style.name == "Normal" and placeholder_style:
-                        new_p.style = doc.styles[placeholder_style]
+                    # 尝试应用样式，逐步降级
+                    applied = _apply_style(new_p, doc, style_name)
+                    if not applied and style_name.startswith("Heading"):
+                        new_p.style = doc.styles["Normal"]
+                    elif not applied:
+                        if placeholder_style:
+                            _apply_style(new_p, doc, placeholder_style)
+                        if new_p.style.name == "Normal" and placeholder_style:
+                            new_p.style = doc.styles[placeholder_style]
 
-                # 继承原段落的编号属性（自动编号）
-                if numPr is not None:
-                    new_pPr = new_p._element.find(qn("w:pPr"))
-                    if new_pPr is None:
-                        new_pPr = new_p._element.makeelement(qn("w:pPr"), {})
-                        new_p._element.insert(0, new_pPr)
-                    existing = new_pPr.find(qn("w:numPr"))
-                    if existing is not None:
-                        new_pPr.remove(existing)
-                    new_pPr.append(deepcopy(numPr))
+                    # 继承原段落的编号属性（自动编号）
+                    if numPr is not None:
+                        new_pPr = new_p._element.find(qn("w:pPr"))
+                        if new_pPr is None:
+                            new_pPr = new_p._element.makeelement(qn("w:pPr"), {})
+                            new_p._element.insert(0, new_pPr)
+                        existing = new_pPr.find(qn("w:numPr"))
+                        if existing is not None:
+                            new_pPr.remove(existing)
+                        new_pPr.append(deepcopy(numPr))
 
-                parent.insert(idx, new_p._element)
+                    parent.insert(idx, new_p._element)
             break
 
     if not placeholder_found:

transit/images.py

@@ -0,0 +1,151 @@
+"""
+图片处理模块。
+
+将 Markdown 中的 ``<img>`` 标签解析为独立段落，
+并在 Word 文档中插入图片及居中图标题。
+"""
+
+import struct
+import re
+
+from docx import Document
+from docx.enum.text import WD_ALIGN_PARAGRAPH
+
+# 匹配 <img src="..." alt="...">
+_IMG_TAG = re.compile(
+    r'<img\s+([^>]*?)src=["\']([^"\']+)["\']([^>]*?)>', re.IGNORECASE
+)
+
+# 从标签属性块中提取名值对
+_ATTR = re.compile(r'(\w+)\s*=\s*["\']([^"\']*)["\']')
+
+# 匹配 **图X ...** 重复图标题（注入时跳过）
+_FIG_CAPTION = re.compile(
+    r'^\*\*(?:图|Table|Figure|Fig\.?)\s*\d+.*\*\*$', re.IGNORECASE
+)
+
+
+def make_image_paragraph(block: str) -> dict | None:
+    """若 *block* 包含 ``<img>`` 标签，返回图片段落字典；否则返回 ``None``。"""
+    m = _IMG_TAG.search(block)
+    if not m:
+        return None
+    attrs = dict(_ATTR.findall(block))
+    return {
+        "type": "image",
+        "src": attrs.get("src", m.group(2)),
+        "alt": attrs.get("alt", ""),
+    }
+
+
+def is_figure_caption(block: str) -> bool:
+    """检查 *block* 是否为 ``**图X ...**`` 格式的重复图标题。"""
+    return bool(_FIG_CAPTION.match(block.strip()))
+
+
+def _get_image_dimensions(image_path: str) -> tuple[int, int] | None:
+    """读取图片文件头返回 ``(width_px, height_px)``，不支持格式返回 ``None``。
+
+    仅读取文件头，不依赖第三方库。支持 PNG / JPEG / GIF / BMP。
+    """
+    try:
+        with open(image_path, "rb") as f:
+            header = f.read(32)
+    except Exception:
+        return None
+
+    # PNG: 8-byte signature, then IHDR chunk
+    if header[:8] == b"\x89PNG\r\n\x1a\n":
+        w, h = struct.unpack_from(">II", header, 16)
+        return w, h
+
+    # JPEG: starts with FF D8, scan for SOF marker
+    if header[:2] == b"\xff\xd8":
+        pos = 2
+        while pos < len(header):
+            if header[pos] != 0xFF:
+                return None
+            marker = header[pos + 1]
+            if marker in (0xC0, 0xC1, 0xC2):
+                h, w = struct.unpack_from(">HH", header, pos + 5)
+                return w, h
+            seg_len = struct.unpack_from(">H", header, pos + 2)[0]
+            pos += 2 + seg_len
+        return None
+
+    # GIF: "GIF87a" or "GIF89a"
+    if header[:6] in (b"GIF87a", b"GIF89a"):
+        w, h = struct.unpack_from("<HH", header, 6)
+        return w, h
+
+    # BMP: "BM" signature
+    if header[:2] == b"BM":
+        w, h = struct.unpack_from("<ii", header, 18)
+        return w, abs(h)
+
+    return None
+
+
+def _get_native_emu(image_path: str) -> int | None:
+    """读取图片的原生宽度（EMU），失败返回 ``None``。
+
+    Word 默认以 72 DPI 渲染图片，1 px = 914400 / 72 = 12700 EMU。
+    """
+    dims = _get_image_dimensions(image_path)
+    if dims is None:
+        return None
+    w_px, _ = dims
+    return w_px * 12700
+
+
+def _constrain_width(image_path: str, page_text_width: int) -> int | None:
+    """返回图片宽度（EMU），超出页宽时缩至页宽。
+
+    Parameters
+    ----------
+    image_path : str
+        图片路径。
+    page_text_width : int
+        页面正文区宽度（EMU），来自 ``section.page_width - margins``。
+    """
+    native = _get_native_emu(image_path)
+    if native is None:
+        return None
+    return min(native, page_text_width)
+
+
+def insert_image_paragraphs(
+    doc: Document,
+    paragraphs: list[dict],
+    *,
+    idx: int,
+    parent,
+):
+    """在 *doc* 的指定位置插入图片段落序列。
+
+    每条图片段落生成两个 Word 段落：
+    1. 居中图片（超出页宽时自动缩放至页宽，否则保持原尺寸）
+    2. 居中图标题（从 ``alt`` 提取）
+
+    插入顺序保持 ``paragraphs`` 的原有顺序。
+    """
+    section = doc.sections[0]
+    page_text_width = section.page_width - section.left_margin - section.right_margin
+
+    for pd_data in reversed(paragraphs):
+        # 图标题（在 reversed 中先插入，最终位于图片下方）
+        cap_p = doc.add_paragraph(pd_data.get("alt", ""))
+        cap_p.alignment = WD_ALIGN_PARAGRAPH.CENTER
+        parent.insert(idx, cap_p._element)
+
+        # 图片段落（max-width 行为：超出页宽时压缩，否则原尺寸）
+        img_p = doc.add_paragraph()
+        img_p.alignment = WD_ALIGN_PARAGRAPH.CENTER
+        img_run = img_p.add_run()
+        try:
+            img_width = _constrain_width(pd_data["src"], page_text_width)
+            img_run.add_picture(pd_data["src"], width=img_width)
+        except Exception as exc:
+            print(f"警告：图片加载失败 {pd_data['src']} — {exc}")
+            img_run.add_text(f"[图片加载失败: {pd_data['src']}]")
+        parent.insert(idx, img_p._element)