add a second fallback method for getting PDF image xrefs per page

dlibrary.py

@@ -111,19 +111,37 @@ def fetch(args):
     asyncio.run(fetch_async(args))
 
 
+def image_xrefs(pdf):
+    images_by_page = [page.get_images() for page in pdf]
+    if all(len(images) == 1 for images in images_by_page):
+        return [images[0][0] for images in images_by_page]
+
+    print("Checking PDF images the quick way failed, trying the slow way")
+    xrefs = []
+    for (idx, page) in enumerate(pdf):
+        print(f'\x1b[2K\r{idx}/{pdf.page_count} pages processed...', end='')
+        images = page.get_image_info(xrefs=True)
+        if len(images) != 1 or images[0]['xref'] == 0:
+            print('\nFailed')
+            return None
+        xrefs.append(images[0]['xref'])
+
+    print('\nSuccess')
+    return xrefs
+
 def link_pdf(src, dest, start_index=0):
     with fitz.open(src) as pdf:
-        images_by_page = [page.get_images() for page in pdf]
-        if all(len(images) == 1 for images in images_by_page):
-            dest.mkdir(parents=True, exist_ok=True)
-            for (idx, images) in enumerate(images_by_page, start=start_index):
-                xref = images[0][0]
-                image = pdf.extract_image(xref)
-                file_path = dest / f'{idx:04d}.{image["ext"]}'
-                with open(file_path, 'wb') as f:
-                    f.write(image["image"])
-        else:
+        xrefs = image_xrefs(pdf)
+        if xrefs is None:
             print(f'Support for weirder PDFs not yet implemented, skipping {src}')
+            return
+
+        dest.mkdir(parents=True, exist_ok=True)
+        for (idx, xref) in enumerate(xrefs, start=start_index):
+            image = pdf.extract_image(xref)
+            file_path = dest / f'{idx:04d}.{image["ext"]}'
+            with open(file_path, 'wb') as f:
+                f.write(image["image"])
 
 def complete_prefix_number_ordering(entries):
     matches = reversed(list(NUMBER_REGEX.finditer(entries[0].name)))