Fix multi-page TIFF image support

Co-authored-by: cau-git <60343111+cau-git@users.noreply.github.com>

docling/backend/pdf_backend.py

@@ -57,7 +57,28 @@ class PdfDocumentBackend(PaginatedDocumentBackend):
             if self.input_format is InputFormat.IMAGE:
                 buf = BytesIO()
                 img = Image.open(self.path_or_stream)
-                img.save(buf, "PDF")
+                
+                # Handle multi-page TIFF images
+                if hasattr(img, 'n_frames') and img.n_frames > 1:
+                    # Extract all frames from multi-page image
+                    frames = []
+                    try:
+                        for i in range(img.n_frames):
+                            img.seek(i)
+                            frames.append(img.copy())
+                    except EOFError:
+                        pass
+                    
+                    # Save as multi-page PDF
+                    if frames:
+                        frames[0].save(buf, "PDF", save_all=True, append_images=frames[1:])
+                    else:
+                        # Fallback to single page if frame extraction fails
+                        img.save(buf, "PDF")
+                else:
+                    # Single page image - use existing behavior
+                    img.save(buf, "PDF")
+                
                 buf.seek(0)
                 self.path_or_stream = buf
             else:

tests/test_multipage_tiff.py

@@ -0,0 +1,139 @@
+import os
+import tempfile
+from pathlib import Path
+from io import BytesIO
+
+import pypdfium2 as pdfium
+from PIL import Image, ImageDraw, ImageFont
+
+from docling.backend.docling_parse_v4_backend import DoclingParseV4DocumentBackend
+from docling.datamodel.base_models import InputFormat
+from docling.datamodel.document import InputDocument
+
+
+def create_test_multipage_image(format_name, num_pages=3):
+    """Create a test multi-page image file."""
+    images = []
+    
+    for i in range(num_pages):
+        # Create a unique image for each page
+        img = Image.new('RGB', (200, 150), color='white')
+        draw = ImageDraw.Draw(img)
+        
+        # Draw page identifier
+        text = f"Page {i+1}"
+        draw.text((10, 10), text, fill='black')
+        
+        # Draw some unique content for each page
+        colors = ['red', 'green', 'blue', 'orange', 'purple']
+        color = colors[i % len(colors)]
+        draw.rectangle([10, 30, 190, 140], outline=color, width=2)
+        
+        images.append(img)
+    
+    # Save as multi-page image
+    suffix = '.tif' if format_name == 'TIFF' else f'.{format_name.lower()}'
+    temp_file = tempfile.NamedTemporaryFile(suffix=suffix, delete=False)
+    temp_file.close()
+    
+    try:
+        if images:
+            images[0].save(temp_file.name, format_name, save_all=True, append_images=images[1:])
+        return temp_file.name
+    except Exception as e:
+        # Clean up on error
+        if os.path.exists(temp_file.name):
+            os.unlink(temp_file.name)
+        raise e
+
+
+def test_multipage_image_support():
+    """Test that multi-page image files are properly handled."""
+    
+    # Test with different image formats and numbers of pages
+    test_cases = [
+        ('TIFF', 1, "single page TIFF"),
+        ('TIFF', 2, "two-page TIFF"),
+        ('TIFF', 3, "three-page TIFF"),
+        ('GIF', 2, "two-page GIF"),
+        ('WEBP', 2, "two-page WEBP"),
+    ]
+    
+    for format_name, num_pages, description in test_cases:
+        print(f"Testing {description}...")
+        
+        # Create test file
+        test_file = create_test_multipage_image(format_name, num_pages)
+        
+        try:
+            # Verify the image has the expected number of pages
+            with Image.open(test_file) as img:
+                expected_pages = getattr(img, 'n_frames', 1)
+                assert expected_pages == num_pages, f"Test {format_name} should have {num_pages} pages, got {expected_pages}"
+            
+            # Test with docling backend
+            input_doc = InputDocument(
+                path_or_stream=Path(test_file),
+                format=InputFormat.IMAGE,
+                backend=DoclingParseV4DocumentBackend
+            )
+            
+            backend = DoclingParseV4DocumentBackend(input_doc, Path(test_file))
+            
+            # Check the page count in the backend
+            actual_pages = backend.page_count()
+            assert actual_pages == expected_pages, f"Backend should report {expected_pages} pages, got {actual_pages}"
+            
+            # Also verify the PDF was created correctly
+            if isinstance(backend.path_or_stream, BytesIO):
+                backend.path_or_stream.seek(0)
+                pdf_doc = pdfium.PdfDocument(backend.path_or_stream)
+                pdf_pages = len(pdf_doc)
+                pdf_doc.close()
+                assert pdf_pages == expected_pages, f"PDF should have {expected_pages} pages, got {pdf_pages}"
+            
+            print(f"✅ {description} passed")
+            
+        finally:
+            # Clean up
+            if os.path.exists(test_file):
+                os.unlink(test_file)
+
+
+def test_single_page_image_unchanged():
+    """Test that single-page image files still work as before."""
+    
+    # Test different single-page formats
+    formats_to_test = ['TIFF', 'GIF', 'WEBP']
+    
+    for format_name in formats_to_test:
+        print(f"Testing single-page {format_name}...")
+        
+        # Create a single-page image
+        test_file = create_test_multipage_image(format_name, 1)
+        
+        try:
+            # Test with docling backend
+            input_doc = InputDocument(
+                path_or_stream=Path(test_file),
+                format=InputFormat.IMAGE,
+                backend=DoclingParseV4DocumentBackend
+            )
+            
+            backend = DoclingParseV4DocumentBackend(input_doc, Path(test_file))
+            
+            # Should have exactly 1 page
+            assert backend.page_count() == 1, f"Single-page {format_name} should have 1 page, got {backend.page_count()}"
+            
+            print(f"✅ Single-page {format_name} test passed")
+            
+        finally:
+            # Clean up
+            if os.path.exists(test_file):
+                os.unlink(test_file)
+
+
+if __name__ == "__main__":
+    test_multipage_image_support()
+    test_single_page_image_unchanged()
+    print("All tests passed!")