diff --git a/camelot/image_processing.py b/camelot/image_processing.py
index 8707d48..3051852 100644
--- a/camelot/image_processing.py
+++ b/camelot/image_processing.py
@@ -97,17 +97,24 @@ def find_lines(threshold, regions=None, direction='horizontal',
         raise ValueError("Specify direction as either 'vertical' or"
                          " 'horizontal'")
 
+    if regions is not None:
+        region_mask = np.zeros(threshold.shape)
+        for region in regions:
+            x, y, w, h = region
+            region_mask[y : y + h, x : x + w] = 1
+        threshold = np.multiply(threshold, region_mask)
+
     threshold = cv2.erode(threshold, el)
     threshold = cv2.dilate(threshold, el)
     dmask = cv2.dilate(threshold, el, iterations=iterations)
 
     try:
         _, contours, _ = cv2.findContours(
-            threshold, cv2.RETR_EXTERNAL, cv2.CHAIN_APPROX_SIMPLE)
+            threshold.astype(np.uint8), cv2.RETR_EXTERNAL, cv2.CHAIN_APPROX_SIMPLE)
     except ValueError:
         # for opencv backward compatibility
         contours, _ = cv2.findContours(
-            threshold, cv2.RETR_EXTERNAL, cv2.CHAIN_APPROX_SIMPLE)
+            threshold.astype(np.uint8), cv2.RETR_EXTERNAL, cv2.CHAIN_APPROX_SIMPLE)
 
     for c in contours:
         x, y, w, h = cv2.boundingRect(c)
@@ -117,12 +124,6 @@ def find_lines(threshold, regions=None, direction='horizontal',
             lines.append(((x1 + x2) // 2, y2, (x1 + x2) // 2, y1))
         elif direction == 'horizontal':
             lines.append((x1, (y1 + y2) // 2, x2, (y1 + y2) // 2))
-    if regions is not None:
-        region_mask = np.zeros(dmask.shape)
-        for region in regions:
-            x, y, w, h = region
-            region_mask[y : y + h, x : x + w] = 1
-        dmask = np.multiply(dmask, region_mask)
 
     return dmask, lines
 
diff --git a/camelot/parsers/lattice.py b/camelot/parsers/lattice.py
index e061f65..ab7d3be 100644
--- a/camelot/parsers/lattice.py
+++ b/camelot/parsers/lattice.py
@@ -232,9 +232,22 @@ class Lattice(BaseParser):
             stderr=subprocess.STDOUT)
 
     def _generate_table_bbox(self):
+        def scale_areas(areas):
+            scaled_areas = []
+            for area in areas:
+                x1, y1, x2, y2 = area.split(",")
+                x1 = float(x1)
+                y1 = float(y1)
+                x2 = float(x2)
+                y2 = float(y2)
+                x1, y1, x2, y2 = scale_pdf((x1, y1, x2, y2), image_scalers)
+                scaled_areas.append((x1, y1, abs(x2 - x1), abs(y2 - y1)))
+            return scaled_areas
+
         self.image, self.threshold = adaptive_threshold(
             self.imagename, process_background=self.process_background,
             blocksize=self.threshold_blocksize, c=self.threshold_constant)
+
         image_width = self.image.shape[1]
         image_height = self.image.shape[0]
         image_width_scaler = image_width / float(self.pdf_width)
@@ -247,15 +260,8 @@ class Lattice(BaseParser):
         if self.table_areas is None:
             regions = None
             if self.table_regions is not None:
-                regions = []
-                for region in self.table_regions:
-                    x1, y1, x2, y2 = region.split(",")
-                    x1 = float(x1)
-                    y1 = float(y1)
-                    x2 = float(x2)
-                    y2 = float(y2)
-                    x1, y1, x2, y2 = scale_pdf((x1, y1, x2, y2), image_scalers)
-                    regions.append((x1, y1, abs(x2 - x1), abs(y2 - y1)))
+                regions = scale_areas(self.table_regions)
+
             vertical_mask, vertical_segments = find_lines(
                 self.threshold, regions=regions, direction='vertical',
                 line_scale=self.line_scale, iterations=self.iterations)
@@ -273,15 +279,7 @@ class Lattice(BaseParser):
                 self.threshold, direction='horizontal', line_scale=self.line_scale,
                 iterations=self.iterations)
 
-            areas = []
-            for area in self.table_areas:
-                x1, y1, x2, y2 = area.split(",")
-                x1 = float(x1)
-                y1 = float(y1)
-                x2 = float(x2)
-                y2 = float(y2)
-                x1, y1, x2, y2 = scale_pdf((x1, y1, x2, y2), image_scalers)
-                areas.append((x1, y1, abs(x2 - x1), abs(y2 - y1)))
+            areas = scale_areas(self.table_areas)
             table_bbox = find_joints(areas, vertical_mask, horizontal_mask)
 
         self.table_bbox_unscaled = copy.deepcopy(table_bbox)