fix：提升图片像素到适应手机3x

app.py

@@ -18,6 +18,7 @@ app = FastAPI(
 async def convert_excel(
     file: UploadFile = File(..., description="The Excel file to convert"),
     sheet_name: str = Form(None, description="Name of the sheet to convert (optional, defaults to active sheet)"),
+    scale: int = Form(3, description="Scaling factor for high-DPI rendering (default 3, best for mobile/retina screens)"),
 ):
     """
     Convert an uploaded Excel file to a PNG image.
@@ -35,7 +36,8 @@ async def convert_excel(
         renderer = ExcelRenderer(contents)
         
         # Render
-        image_bytes = renderer.render_to_bytes(sheet_name=sheet_name)
+        # Use scale parameter
+        image_bytes = renderer.render_to_bytes(sheet_name=sheet_name, scale=scale)
         
         # Return as streaming response
         # Handle Chinese filenames in Content-Disposition

core/renderer.py

@@ -51,18 +51,19 @@ class ExcelRenderer:
         self.font_cache[key] = font
         return font
 
-    def render_to_bytes(self, sheet_name: Optional[str] = None, dpi: int = 200, padding: int = 20) -> bytes:
+    def render_to_bytes(self, sheet_name: Optional[str] = None, dpi: int = 300, padding: int = 20, scale: int = 2) -> bytes:
         """
         Render the specified sheet to a PNG image and return bytes.
+        :param scale: Internal scaling factor for high-DPI rendering (default 2x).
         """
-        img = self._render_image(sheet_name, padding)
+        img = self._render_image(sheet_name, padding, scale)
         
         output = io.BytesIO()
         img.save(output, format='PNG', dpi=(dpi, dpi))
         output.seek(0)
         return output.getvalue()
 
-    def _render_image(self, sheet_name: Optional[str], padding: int) -> Image.Image:
+    def _render_image(self, sheet_name: Optional[str], padding: int, scale: int) -> Image.Image:
         """
         Internal method to draw the Excel sheet onto a PIL Image.
         """
@@ -76,10 +77,11 @@ class ExcelRenderer:
             else:
                 raise ValueError(f"Sheet '{sheet_name}' not found. Available sheets: {wb.sheetnames}")
 
-        return self._draw_sheet(sheet, padding)
+        return self._draw_sheet(sheet, padding, scale)
 
-    def _draw_sheet(self, sheet: Worksheet, padding: int) -> Image.Image:
-        cell_height = 40  # Default cell height
+    def _draw_sheet(self, sheet: Worksheet, padding: int, scale: int) -> Image.Image:
+        cell_height = 40 * scale # Scaled cell height
+        padding = padding * scale # Scaled padding
         
         max_row = sheet.max_row
         max_col = sheet.max_column
@@ -95,7 +97,8 @@ class ExcelRenderer:
             col_width_excel = col_dim.width if col_dim.width else 10
             
             # Excel width to pixels (approximate factor ~7 + padding)
-            width_px = int(col_width_excel * 7) + 5
+            # Apply scale factor
+            width_px = int((col_width_excel * 7 + 5) * scale)
             col_widths_pixels.append(width_px)
             img_width += width_px
 
@@ -134,7 +137,7 @@ class ExcelRenderer:
                     # Use the max_row of the merged range to determine y2
                     y2 = padding + max_r * cell_height
                     
-                    self._draw_cell(draw, cell, x1, y1, x2, y2)
+                    self._draw_cell(draw, cell, x1, y1, x2, y2, scale)
                     
                 # Skip if it is a merged cell but NOT the top-left (already handled above or by MergedCell check)
                 elif isinstance(cell, MergedCell):
@@ -147,11 +150,11 @@ class ExcelRenderer:
                     x2 = col_x_positions[col]
                     y2 = y1 + cell_height
 
-                    self._draw_cell(draw, cell, x1, y1, x2, y2)
+                    self._draw_cell(draw, cell, x1, y1, x2, y2, scale)
 
         return img
 
-    def _draw_cell(self, draw: ImageDraw.ImageDraw, cell, x1, y1, x2, y2):
+    def _draw_cell(self, draw: ImageDraw.ImageDraw, cell, x1, y1, x2, y2, scale: int):
         # Skip MergedCells that are not the top-left cell
         if isinstance(cell, MergedCell):
             return
@@ -176,7 +179,9 @@ class ExcelRenderer:
         is_bold = cell.font and cell.font.bold
         # Excel font size is in points. 12 is default.
         font_size = int(cell.font.sz) if (cell.font and cell.font.sz) else 12
-        current_font = self._get_font(is_bold, font_size)
+        # Scale the font size
+        scaled_font_size = int(font_size * scale)
+        current_font = self._get_font(is_bold, scaled_font_size)
         
         # Font color
         # Excel's Color object can be complex. We pass the whole object to _parse_color.
@@ -188,7 +193,7 @@ class ExcelRenderer:
         v_align = cell.alignment.vertical if (cell.alignment and cell.alignment.vertical) else 'center'
 
         # Text rendering with simple truncation
-        self._draw_text(draw, text, x1, y1, x2, y2, current_font, text_color, h_align, v_align, font_size)
+        self._draw_text(draw, text, x1, y1, x2, y2, current_font, text_color, h_align, v_align, scaled_font_size)
 
     def _parse_color(self, color_obj, default=(0, 0, 0)) -> Tuple[int, int, int]:
         """

tests/test_high_dpi.py

@@ -0,0 +1,31 @@
+import pytest
+import io
+import os
+from core.renderer import ExcelRenderer
+from PIL import Image
+
+TEST_FILE_PATH = "tests/kshj_gt1767081783800.xlsx"
+
+@pytest.mark.skipif(not os.path.exists(TEST_FILE_PATH), reason="Test file not found")
+def test_high_dpi_rendering():
+    """
+    Test rendering with higher scale factor.
+    """
+    with open(TEST_FILE_PATH, "rb") as f:
+        content = f.read()
+    
+    renderer = ExcelRenderer(content)
+    
+    # Render with scale=3 (High Quality)
+    img_bytes = renderer.render_to_bytes(scale=3, dpi=300)
+    
+    assert isinstance(img_bytes, bytes)
+    assert len(img_bytes) > 0
+    
+    img = Image.open(io.BytesIO(img_bytes))
+    
+    # Save for visual inspection
+    output_path = "tests/test_output_high_dpi.png"
+    img.save(output_path)
+    print(f"Generated high DPI test image at: {os.path.abspath(output_path)}")
+    print(f"Image Size: {img.size}")