Provide a helper for determing segm mask format

Reviewed By: rbgirshick

Differential Revision: D8836361

fbshipit-source-id: f7d8bad14e0d6309ae349616f2b837d7082e2d74

detectron/datasets/json_dataset.py

@@ -43,6 +43,7 @@ from detectron.core.config import cfg
 from detectron.utils.timer import Timer
 import detectron.datasets.dataset_catalog as dataset_catalog
 import detectron.utils.boxes as box_utils
+import detectron.utils.segms as segm_utils
 
 logger = logging.getLogger(__name__)
 
@@ -167,8 +168,8 @@ class JsonDataset(object):
         width = entry['width']
         height = entry['height']
         for obj in objs:
-            # crowd regions are RLE encoded and stored as dicts
-            if isinstance(obj['segmentation'], list):
+            # crowd regions are RLE encoded
+            if segm_utils.is_poly(obj['segmentation']):
                 # Valid polygons have >= 3 points, so require >= 6 coordinates
                 obj['segmentation'] = [
                     p for p in obj['segmentation'] if len(p) >= 6

detectron/utils/segms.py

@@ -31,6 +31,18 @@ import numpy as np
 
 import pycocotools.mask as mask_util
 
+# Type used for storing masks in polygon format
+_POLY_TYPE = list
+# Type used for storing masks in RLE format
+_RLE_TYPE = dict
+
+
+def is_poly(segm):
+    """Determine if segm is a polygon. Valid segm expected (polygon or RLE)."""
+    assert isinstance(segm, (_POLY_TYPE, _RLE_TYPE)), \
+        'Invalid segm type: {}'.format(type(segm))
+    return isinstance(segm, _POLY_TYPE)
+
 
 def flip_segms(segms, height, width):
     """Left/right flip each mask in a list of masks."""
@@ -51,12 +63,11 @@ def flip_segms(segms, height, width):
 
     flipped_segms = []
     for segm in segms:
-        if type(segm) == list:
+        if is_poly(segm):
             # Polygon format
             flipped_segms.append([_flip_poly(poly, width) for poly in segm])
         else:
             # RLE format
-            assert type(segm) == dict
             flipped_segms.append(_flip_rle(segm, height, width))
     return flipped_segms