Add function to group contiguous objects

Author: turicas

rows/plugins/plugin_ocr.py

@@ -21,10 +21,56 @@
 from pytesseract import image_to_boxes
 from PIL import Image
 
-from rows.plugins.plugin_pdf import PDFBackend, TextObject, pdf_table_lines
+from rows.plugins.plugin_pdf import group_objects, PDFBackend, TextObject, pdf_table_lines
 from rows.plugins.utils import create_table
 
 
+def join_text_group(group):
+    """Join a list of `TextObject`s into one"""
+
+    obj = group[0]
+    max_between = (obj.x1 - obj.x0) / len(obj.text)  # Average letter size
+    text, last_x1 = [], obj.x0
+    for obj in group:
+        if last_x1 + max_between <= obj.x0:
+            text.append(" ")
+        text.append(obj.text)
+        last_x1 = obj.x1
+    text = "".join(text)
+
+    return TextObject(
+        x0=min(obj.x0 for obj in group),
+        y0=min(obj.y0 for obj in group),
+        x1=max(obj.x1 for obj in group),
+        y1=max(obj.y1 for obj in group),
+        text=text
+    )
+
+
+def group_contiguous_objects(objs, x_threshold, y_threshold):
+    """Merge contiguous objects if they're closer enough"""
+
+    objs.sort(key=lambda obj: obj.y0)
+    y_groups = group_objects(objs, y_threshold, "y")
+    for y_group, y_items in y_groups.items():
+        y_items.sort(key=lambda obj: obj.x0)
+
+        x_groups, current_group, last_x1 = [], [], None
+        for obj in y_items:
+            if not current_group or last_x1 + x_threshold >= obj.x0:
+                current_group.append(obj)
+            elif current_group:
+                x_groups.append(current_group)
+                current_group = [obj]
+            last_x1 = obj.x1
+        if current_group:
+            x_groups.append(current_group)
+
+        for group in x_groups:
+            if group:
+                yield join_text_group(group)
+
+
 class TesseractBackend(PDFBackend):
 
     name = "tesseract"
@@ -36,12 +82,7 @@ def __init__(self, filename_or_fobj, language):
 
     @cached_property
     def document(self):
-        if hasattr(self.filename_or_fobj, "read"):
-            image = Image.open(self.filename_or_fobj)
-        else:
-            image = self.filename_or_fobj
-
-        return image
+        return Image.open(self.filename_or_fobj)
 
     @cached_property
     def number_of_pages(self):
@@ -51,6 +92,7 @@ def extract_text(self, page_numbers=None):
         return ""  # TODO: image_to_string
 
     def objects(self, page_numbers=None, starts_after=None, ends_before=None):
+        _, total_y = self.document.size
         header = "char left bottom right top page".split()
         boxes = image_to_boxes(self.document, lang=self.language).splitlines()
         text_objs = []
@@ -60,18 +102,18 @@ def objects(self, page_numbers=None, starts_after=None, ends_before=None):
                 if key != "char":
                     value = int(value)
                 row[key] = value
-            obj = TextObject(
-                x0=row["left"],
-                y0=row["bottom"],
-                x1=row["right"],
-                y1=row["top"],
-                text=row["char"],
+            text_objs.append(
+                TextObject(
+                    x0=row["left"],
+                    y0=total_y - row["bottom"],
+                    x1=row["right"],
+                    y1=total_y - row["top"],
+                    text=row["char"],
+                )
             )
-            text_objs.append(obj)
 
-        text_objs.sort(key=lambda obj: (obj.y0, obj.x0))
-        # TODO: group contiguous objects before yielding
-        yield text_objs
+        # TODO: custom thresholds
+        yield list(group_contiguous_objects(text_objs, 30, 12))
 
     text_objects = objects