Experimental qpdf merging

Does not copy /Catalog metadata, but otherwise functional

ocrmypdf/main.py

@@ -1119,8 +1119,10 @@ def merge_pages(
         return key
 
     pdf_pages = sorted(input_files, key=input_file_order)
-    log.debug("Final pages: " + "\n".join(pdf_pages))
-    ghostscript.generate_pdfa(pdf_pages, output_file, options.jobs or 1)
+    #log.debug("Final pages: " + "\n".join(pdf_pages))
+    #ghostscript.generate_pdfa(pdf_pages, output_file, options.jobs or 1)
+    pdf_pages.pop()
+    qpdf.merge(pdf_pages, output_file)
 
 
 @transform(

ocrmypdf/qpdf.py

@@ -85,3 +85,15 @@ def split_pages(input_file, work_folder, npages):
             os.path.join(work_folder, '{0:06d}.page.pdf'.format(n + 1))
         ]
         check_call(args_qpdf)
+
+
+def merge(input_files, output_file):
+    """Merge the list of input files (all filenames) into the output file.
+
+    The input files may contain one or more pages.
+    """
+    args_qpdf = [
+        get_program('qpdf'), input_files[0], '--pages'
+    ] + input_files + ['--', output_file]
+    check_call(args_qpdf)
+