Provisionally add filters

src/ocrmypdf/_pipeline.py

@@ -521,6 +521,9 @@ def create_ocr_image(image, page_context):
                     draw.rectangle(rect, fill=white)
             im = pix.topil()
 
+        if options.filter_ocr_image:
+            im = options.filter_ocr_image(im)
+
         del draw
         # Pillow requires integer DPI
         dpi = round(xres), round(yres)

src/ocrmypdf/api.py

@@ -113,10 +113,14 @@ def configure_logging(verbosity, progress_bar_friendly=True, manage_root_logger=
 
 def create_options(*, input_file, output_file, **kwargs):
     cmdline = []
+    filters = []
 
     for arg, val in kwargs.items():
         if val is None:
             continue
+        if arg.startswith('filter') and callable(val):
+            filters.append((arg, val))
+            continue
         cmd_style_arg = arg.replace('_', '-')
         cmdline.append(f"--{cmd_style_arg}")
         if isinstance(val, bool):
@@ -135,6 +139,8 @@ def create_options(*, input_file, output_file, **kwargs):
 
     parser.api_mode = True
     options = parser.parse_args(cmdline)
+    for keyword, function in filters:
+        setattr(options, keyword, function)
     return options
 
 

src/ocrmypdf/cli.py

@@ -466,6 +466,10 @@ advanced.add_argument(
     help="Specify the location of the Tesseract user patterns file.",
 )
 
+
+filters = parser.add_argument_group("Filters", argparse.SUPPRESS)
+filters.add_argument('--filter-ocr-image', help=argparse.SUPPRESS)
+
 debugging = parser.add_argument_group(
     "Debugging", "Arguments to help with troubleshooting and debugging"
 )