Segmentation polygons2masks_overlap() in np.int32 (#9493)

* Segmentation `polygons2masks_overlap()` in `np.int32`

May resolve #9461

WARNING: Masks should be uint8 for fastest speed, change needs profiling results to determine impact.

@AyushExel @Laughing-q 

Signed-off-by: Glenn Jocher <glenn.jocher@ultralytics.com>

* Update dataloaders.py

Signed-off-by: Glenn Jocher <glenn.jocher@ultralytics.com>

* [pre-commit.ci] auto fixes from pre-commit.com hooks

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Signed-off-by: Glenn Jocher <glenn.jocher@ultralytics.com>
Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

utils/segment/dataloaders.py

@@ -308,7 +308,8 @@ def polygons2masks(img_size, polygons, color, downsample_ratio=1):
 
 def polygons2masks_overlap(img_size, segments, downsample_ratio=1):
     """Return a (640, 640) overlap mask."""
-    masks = np.zeros((img_size[0] // downsample_ratio, img_size[1] // downsample_ratio), dtype=np.uint8)
+    masks = np.zeros((img_size[0] // downsample_ratio, img_size[1] // downsample_ratio),
+                     dtype=np.int32 if len(segments) > 255 else np.uint8)
     areas = []
     ms = []
     for si in range(len(segments)):