fix: 修复社区暂存主题并为函数图例添加数学排版

backend/app/export/assets.py

@@ -114,6 +114,7 @@ def plot_png(plot):
     """按 SVG/PDF 共用的裁剪几何，以二倍分辨率生成 DOCX 图像。"""
     from app.plot.render import compute_geometry, _sx, _sy, _fmt_num
     from PIL import ImageDraw, ImageFont
+    from app.plot.math_label import expression_latex, render_math_mask
     geo = compute_geometry(plot)
     image = Image.new('RGB', (geo.width * 2, (geo.height + ((len(plot.expressions)+1)//2)*24) * 2), 'white')
     draw = ImageDraw.Draw(image)
@@ -140,6 +141,13 @@ def plot_png(plot):
         # 纵轴标题横排在左上边距，避免 CJK 文本在 Word 中旋转后不可读。
         draw.text((24, 24), geo.ylabel, fill='#1f2328', font=font)
     for index, expression in enumerate(plot.expressions):
-        draw.text((48+(index%2)*620,geo.height*2+index//2*48),expression.label or 'y = '+expression.expression,fill=geo.colors[index],font=font)
+        position = (48 + (index % 2) * 620, geo.height * 2 + 8 + (index // 2) * 48)
+        if expression.label:
+            draw.text(position, expression.label, fill=geo.colors[index], font=font)
+        else:
+            mask_width, mask_height, mask_bytes = render_math_mask(expression_latex(expression.expression))
+            mask = Image.frombytes('L', (mask_width, mask_height), mask_bytes)
+            ink = Image.new('RGB', mask.size, geo.colors[index])
+            image.paste(ink, position, mask)
     out=BytesIO(); image.save(out,'PNG')
     return out.getvalue(), geo.warnings

backend/app/plot/math_label.py

@@ -0,0 +1,189 @@
+"""Safe AST-to-LaTeX conversion and vector math layout for plot labels."""
+
+from __future__ import annotations
+
+import ast
+import html
+import math
+import threading
+from dataclasses import dataclass
+from functools import lru_cache
+
+from matplotlib.font_manager import FontProperties
+from matplotlib.mathtext import MathTextParser
+from matplotlib.path import Path as MplPath
+
+from app.plot.parser import parse_expression
+
+_MATH_PARSER = MathTextParser("path")
+_RASTER_PARSER = MathTextParser("agg")
+_MATH_LOCK = threading.Lock()
+
+
+def _number(value: int | float) -> str:
+    text = repr(value)
+    if "e" not in text.lower():
+        return text
+    mantissa, exponent = text.lower().split("e", 1)
+    return rf"{mantissa}\times 10^{{{int(exponent)}}}"
+
+
+def _latex(node: ast.AST, parent_precedence: int = 0) -> str:
+    if isinstance(node, ast.Constant):
+        return _number(node.value)
+    if isinstance(node, ast.Name):
+        return r"\pi" if node.id == "pi" else node.id
+    if isinstance(node, ast.UnaryOp):
+        value = _latex(node.operand, 25)
+        result = ("-" if isinstance(node.op, ast.USub) else "+") + value
+        return rf"\left({result}\right)" if parent_precedence > 25 else result
+    if isinstance(node, ast.BinOp):
+        if isinstance(node.op, ast.Div):
+            return rf"\frac{{{_latex(node.left)}}}{{{_latex(node.right)}}}"
+        if isinstance(node.op, ast.Pow):
+            result = rf"{{{_latex(node.left, 30)}}}^{{{_latex(node.right)}}}"
+            return rf"\left({result}\right)" if parent_precedence > 30 else result
+        precedence = 20 if isinstance(node.op, ast.Mult) else 10
+        operator = r" \cdot " if isinstance(node.op, ast.Mult) else (" + " if isinstance(node.op, ast.Add) else " - ")
+        left = _latex(node.left, precedence)
+        right = _latex(node.right, precedence + (1 if isinstance(node.op, ast.Sub) else 0))
+        result = left + operator + right
+        return rf"\left({result}\right)" if parent_precedence > precedence else result
+    if isinstance(node, ast.Call) and isinstance(node.func, ast.Name):
+        argument = _latex(node.args[0])
+        name = node.func.id
+        if name == "sqrt":
+            return rf"\sqrt{{{argument}}}"
+        if name == "abs":
+            return rf"\left|{argument}\right|"
+        if name in {"log10", "log2"}:
+            return rf"\log_{{{name[3:]}}}\left({argument}\right)"
+        if name in {"asin", "acos", "atan"}:
+            return rf"\{name[1:]}^{{-1}}\left({argument}\right)"
+        command = "log" if name == "ln" else name
+        return rf"\{command}\left({argument}\right)"
+    raise ValueError(f"Unsupported validated expression node: {type(node).__name__}")
+
+
+def expression_latex(expression: str) -> str:
+    """Convert one already-supported function expression to MathText-compatible LaTeX."""
+    return "y = " + _latex(parse_expression(expression).body)
+
+
+@dataclass(frozen=True)
+class VectorPath:
+    commands: tuple[tuple[str, tuple[float, ...]], ...]
+
+
+@dataclass(frozen=True)
+class MathLayout:
+    width: float
+    height: float
+    depth: float
+    paths: tuple[VectorPath, ...]
+    rects: tuple[tuple[float, float, float, float], ...]
+
+
+def _offset(values: tuple[float, ...], x: float, y: float) -> tuple[float, ...]:
+    return tuple(value + (x if index % 2 == 0 else y) for index, value in enumerate(values))
+
+
+@lru_cache(maxsize=256)
+def math_layout(latex: str, size: float = 12.0) -> MathLayout:
+    """Lay out LaTeX as reusable vector paths; calls are cached and serialized for FT2Font."""
+    with _MATH_LOCK:
+        parsed = _MATH_PARSER.parse(f"${latex}$", dpi=72, prop=FontProperties(size=size))
+        paths: list[VectorPath] = []
+        for font, font_size, _character, glyph, offset_x, offset_y in parsed.glyphs:
+            font.set_size(font_size, 72)
+            font.load_glyph(glyph)
+            vertices, codes = font.get_path()
+            commands: list[tuple[str, tuple[float, ...]]] = []
+            for values, code in MplPath(vertices, codes).iter_segments(curves=True, simplify=False):
+                command = {
+                    MplPath.MOVETO: "M",
+                    MplPath.LINETO: "L",
+                    MplPath.CURVE3: "Q",
+                    MplPath.CURVE4: "C",
+                    MplPath.CLOSEPOLY: "Z",
+                }[code]
+                points = () if command == "Z" else _offset(tuple(float(value) for value in values), float(offset_x), float(offset_y))
+                commands.append((command, points))
+            paths.append(VectorPath(tuple(commands)))
+        rects = tuple(tuple(float(value) for value in rect) for rect in parsed.rects)
+        return MathLayout(float(parsed.width), float(parsed.height), float(parsed.depth), tuple(paths), rects)
+
+
+def _svg_number(value: float) -> str:
+    if math.isclose(value, round(value), abs_tol=1e-8):
+        return str(int(round(value)))
+    return f"{value:.4f}".rstrip("0").rstrip(".")
+
+
+def _svg_path(path: VectorPath) -> str:
+    return " ".join(command + (" " + " ".join(_svg_number(value) for value in values) if values else "") for command, values in path.commands)
+
+
+def render_math_svg(latex: str, *, x: float, top: float, class_name: str, color: str) -> str:
+    """Return a script-free SVG group containing MathText vector glyphs."""
+    layout = math_layout(latex)
+    baseline = top + layout.height - layout.depth
+    accessible = html.escape(latex, quote=True)
+    parts = [
+        f'<g class="{class_name} plot-math-label" fill="{color}" '
+        f'transform="translate({_svg_number(x)} {_svg_number(baseline)}) scale(1 -1)" '
+        f'aria-label="{accessible}" data-latex="{accessible}">'
+    ]
+    parts.extend(f'<path d="{_svg_path(path)}"/>' for path in layout.paths)
+    for rx, ry, width, height in layout.rects:
+        parts.append(
+            f'<path d="M {_svg_number(rx)} {_svg_number(ry)} h {_svg_number(width)} '
+            f'v {_svg_number(height)} h -{_svg_number(width)} Z"/>'
+        )
+    parts.append("</g>")
+    return "".join(parts)
+
+
+def render_math_reportlab(latex: str, *, x: float, visual_top: float, color: object):
+    """Return a reportlab Group containing the same LaTeX glyph geometry as the SVG."""
+    from reportlab.graphics.shapes import Group, Path, Rect
+
+    layout = math_layout(latex)
+    baseline = visual_top - (layout.height - layout.depth)
+    group = Group()
+    for vector in layout.paths:
+        path = Path(fillColor=color, strokeColor=None)
+        current = (0.0, 0.0)
+        start = current
+        for command, values in vector.commands:
+            if command == "M":
+                current = (values[0], values[1]); start = current
+                path.moveTo(*current)
+            elif command == "L":
+                current = (values[0], values[1]); path.lineTo(*current)
+            elif command == "Q":
+                control, end = (values[0], values[1]), (values[2], values[3])
+                first = (current[0] + 2 * (control[0] - current[0]) / 3,
+                         current[1] + 2 * (control[1] - current[1]) / 3)
+                second = (end[0] + 2 * (control[0] - end[0]) / 3,
+                          end[1] + 2 * (control[1] - end[1]) / 3)
+                path.curveTo(*first, *second, *end); current = end
+            elif command == "C":
+                path.curveTo(*values); current = (values[4], values[5])
+            else:
+                path.closePath(); current = start
+        group.add(path)
+    for rx, ry, width, height in layout.rects:
+        group.add(Rect(rx, ry, width, height, fillColor=color, strokeColor=None))
+    group.translate(x, baseline)
+    return group
+
+
+@lru_cache(maxsize=256)
+def render_math_mask(latex: str, size: float = 12.0, dpi: float = 144.0) -> tuple[int, int, bytes]:
+    """Rasterize LaTeX to an 8-bit alpha mask for DOCX/PNG export."""
+    with _MATH_LOCK:
+        parsed = _RASTER_PARSER.parse(f"${latex}$", dpi=dpi, prop=FontProperties(size=size))
+        image = parsed.image
+        height, width = image.shape
+        return int(width), int(height), image.tobytes()

backend/app/plot/render.py

@@ -16,6 +16,7 @@ import re
 from dataclasses import dataclass
 
 from app.plot.model import FunctionPlot, StaticRenderResult
+from app.plot.math_label import expression_latex, render_math_svg
 from app.plot.parser import PlotParseError, evaluate, parse_expression
 
 _WIDTH = 640
@@ -491,9 +492,13 @@ def render_svg(plot: FunctionPlot, theme_id: str = 'light', unlimited: bool = Fa
     parts.append(_labels_svg(geo))
     for index, expression in enumerate(plot.expressions):
         x = 24 + (index % 2) * 310
-        y = geo.height + 18 + (index // 2) * 24
-        label = html.escape(expression.label or ('y = ' + expression.expression))
-        parts.append(f'<text x="{x}" y="{y}" font-size="12" fill="{geo.colors[index]}" class="plot-legend-{index % 6}">{label}</text>')
+        top = geo.height + 4 + (index // 2) * 24
+        if expression.label:
+            label = html.escape(expression.label)
+            parts.append(f'<text x="{x}" y="{top + 14}" font-size="12" fill="{geo.colors[index]}" class="plot-legend-{index % 6}">{label}</text>')
+        else:
+            parts.append(render_math_svg(expression_latex(expression.expression), x=x, top=top,
+                                         class_name=f"plot-legend-{index % 6}", color=geo.colors[index]))
     parts.append("</svg>")
 
     return StaticRenderResult(

backend/app/plot/render_reportlab.py

@@ -15,6 +15,7 @@ from reportlab.pdfbase import pdfmetrics
 from reportlab.pdfbase.cidfonts import UnicodeCIDFont
 
 from app.plot.model import FunctionPlot
+from app.plot.math_label import expression_latex, render_math_reportlab
 from app.plot.render import PlotGeometry, _fmt_num, _sx, _sy, compute_geometry
 
 from app.export.fonts import FONT as _FONT
@@ -125,8 +126,14 @@ def render_drawing(plot: FunctionPlot, width: float | None = None, palette=None,
     legend_height = ((len(plot.expressions)+1)//2)*24
     drawing.height += legend_height
     for index, expression in enumerate(plot.expressions):
-        drawing.add(String(24+(index%2)*310,geo.height+legend_height-18-(index//2)*24,
-            expression.label or 'y = '+expression.expression,fontName=_FONT,fontSize=12,fillColor=HexColor(geo.colors[index])))
+        x = 24 + (index % 2) * 310
+        visual_top = drawing.height - 4 - (index // 2) * 24
+        if expression.label:
+            drawing.add(String(x, visual_top - 12, expression.label, fontName=_FONT, fontSize=12,
+                               fillColor=HexColor(geo.colors[index])))
+        else:
+            drawing.add(render_math_reportlab(expression_latex(expression.expression), x=x,
+                                               visual_top=visual_top, color=HexColor(geo.colors[index])))
     if width is not None and width > 0:
         drawing.renderScale = min(1.0, width / geo.width, max_height / drawing.height if max_height else 1.0)
     return drawing