feat: add pypdfium2 rasterization plugin for OCRmyPDF

Co-authored-by: aider (anthropic/claude-sonnet-4-20250514) <aider@aider.chat>

src/ocrmypdf/builtin_plugins/pypdfium.py

@@ -0,0 +1,127 @@
+# SPDX-FileCopyrightText: 2024 James R. Barlow
+# SPDX-License-Identifier: MPL-2.0
+"""Built-in plugin to implement PDF page rasterization using pypdfium2."""
+
+from __future__ import annotations
+
+import logging
+from pathlib import Path
+
+try:
+    import pypdfium2 as pdfium
+except ImportError:
+    pdfium = None
+
+from ocrmypdf import hookimpl
+from ocrmypdf.exceptions import MissingDependencyError
+from ocrmypdf.helpers import Resolution
+
+log = logging.getLogger(__name__)
+
+
+@hookimpl
+def check_options(options):
+    """Check that pypdfium2 is available."""
+    if pdfium is None:
+        raise MissingDependencyError(
+            "pypdfium2 is required for this plugin. Install it with: pip install pypdfium2"
+        )
+
+
+@hookimpl
+def rasterize_pdf_page(
+    input_file: Path,
+    output_file: Path,
+    raster_device: str,
+    raster_dpi: Resolution,
+    pageno: int,
+    page_dpi: Resolution | None,
+    rotation: int | None,
+    filter_vector: bool,
+    stop_on_soft_error: bool,
+) -> Path:
+    """Rasterize a single page of a PDF file using pypdfium2."""
+    if pdfium is None:
+        raise MissingDependencyError("pypdfium2 is not available")
+    
+    # Open the PDF document
+    pdf = pdfium.PdfDocument(input_file)
+    
+    try:
+        # Get the specific page (pypdfium2 uses 0-based indexing)
+        page = pdf.get_page(pageno - 1)
+        
+        try:
+            # Calculate the scale factor based on DPI
+            # pypdfium2 uses points (72 DPI) as base unit
+            scale = float(raster_dpi.x) / 72.0
+            
+            # Apply rotation if specified
+            if rotation:
+                # pypdfium2 rotation is in degrees, same as our input
+                page.set_rotation(rotation)
+            
+            # Render the page to a bitmap
+            # The scale parameter controls the resolution
+            bitmap = page.render(
+                scale=scale,
+                rotation=0,  # We already set rotation on the page
+                crop=None,
+                may_draw_forms=True,
+                may_draw_annots=True,
+                # Note: pypdfium2 doesn't have a direct equivalent to filter_vector
+                # This would require more complex implementation if needed
+            )
+            
+            try:
+                # Convert to PIL Image
+                pil_image = bitmap.to_pil()
+                
+                # Set the DPI metadata if page_dpi is specified
+                if page_dpi:
+                    # PIL expects DPI as a tuple
+                    dpi_tuple = (float(page_dpi.x), float(page_dpi.y))
+                    pil_image.info['dpi'] = dpi_tuple
+                else:
+                    # Use the raster DPI
+                    dpi_tuple = (float(raster_dpi.x), float(raster_dpi.y))
+                    pil_image.info['dpi'] = dpi_tuple
+                
+                # Determine output format based on raster_device
+                if raster_device.lower() in ('png', 'png16m', 'pngalpha'):
+                    format_name = 'PNG'
+                elif raster_device.lower() in ('jpeg', 'jpg'):
+                    format_name = 'JPEG'
+                    # Convert RGBA to RGB for JPEG
+                    if pil_image.mode == 'RGBA':
+                        # Create white background
+                        background = pil_image.new('RGB', pil_image.size, (255, 255, 255))
+                        background.paste(pil_image, mask=pil_image.split()[-1])  # Use alpha channel as mask
+                        pil_image = background
+                elif raster_device.lower() in ('tiff', 'tif'):
+                    format_name = 'TIFF'
+                else:
+                    # Default to PNG for unknown formats
+                    format_name = 'PNG'
+                    if stop_on_soft_error:
+                        raise ValueError(f"Unsupported raster device: {raster_device}")
+                    else:
+                        log.warning(f"Unsupported raster device {raster_device}, using PNG")
+                
+                # Save the image
+                save_kwargs = {}
+                if format_name in ('PNG', 'TIFF') and 'dpi' in pil_image.info:
+                    save_kwargs['dpi'] = pil_image.info['dpi']
+                elif format_name == 'JPEG' and 'dpi' in pil_image.info:
+                    save_kwargs['dpi'] = pil_image.info['dpi']
+                
+                pil_image.save(output_file, format=format_name, **save_kwargs)
+                
+            finally:
+                bitmap.close()
+        finally:
+            page.close()
+    finally:
+        pdf.close()
+    
+    return output_file