[Fix] Fix bitmap mask translate when out_shape is different. (#8993)

* [Fix] Fix bitmap mask translate when out_shape is different.

* fix corner case

* fix filename

mmdet/structures/mask/structures.py

@@ -422,7 +422,6 @@ def translate(self,
             >>> border_value = 0
             >>> interpolation = 'bilinear'
             >>> # Note, There seem to be issues when:
-            >>> # * out_shape is different than self's shape
             >>> # * the mask dtype is not supported by cv2.AffineWarp
             >>> new = self.translate(out_shape, offset, direction,
             >>>                      border_value, interpolation)
@@ -432,8 +431,16 @@ def translate(self,
         if len(self.masks) == 0:
             translated_masks = np.empty((0, *out_shape), dtype=np.uint8)
         else:
+            masks = self.masks
+            if masks.shape[-2:] != out_shape:
+                empty_masks = np.zeros((masks.shape[0], *out_shape),
+                                       dtype=masks.dtype)
+                min_h = min(out_shape[0], masks.shape[1])
+                min_w = min(out_shape[1], masks.shape[2])
+                empty_masks[:, :min_h, :min_w] = masks[:, :min_h, :min_w]
+                masks = empty_masks
             translated_masks = mmcv.imtranslate(
-                self.masks.transpose((1, 2, 0)),
+                masks.transpose((1, 2, 0)),
                 offset,
                 direction,
                 border_value=border_value,

tests/test_structures/test_mask/test_mask_structures.py

@@ -0,0 +1,43 @@
+from unittest import TestCase
+
+import numpy as np
+from mmengine.testing import assert_allclose
+
+from mmdet.structures.mask import BitmapMasks
+
+
+class TestMaskStructures(TestCase):
+
+    def test_bitmap_translate_same_size(self):
+        mask_array = np.zeros((5, 10, 10), dtype=np.uint8)
+        mask_array[:, 0:5, 0:5] = 1
+        mask_target = np.zeros((5, 10, 10), dtype=np.uint8)
+        mask_target[:, 0:5, 5:10] = 1
+
+        mask = BitmapMasks(mask_array, 10, 10)
+        mask = mask.translate((10, 10), 5)
+        assert mask.masks.shape == (5, 10, 10)
+        assert_allclose(mask_target, mask.masks)
+
+    def test_bitmap_translate_diff_size(self):
+        # test out shape larger
+        mask_array = np.zeros((5, 10, 10), dtype=np.uint8)
+        mask_array[:, 0:5, 0:5] = 1
+
+        mask_target = np.zeros((5, 20, 20), dtype=np.uint8)
+        mask_target[:, 0:5, 5:10] = 1
+        mask = BitmapMasks(mask_array, 10, 10)
+        mask = mask.translate((20, 20), 5)
+        assert mask.masks.shape == (5, 20, 20)
+        assert_allclose(mask_target, mask.masks)
+
+        # test out shape smaller
+        mask_array = np.zeros((5, 10, 10), dtype=np.uint8)
+        mask_array[:, 0:5, 0:5] = 1
+
+        mask_target = np.zeros((5, 20, 8), dtype=np.uint8)
+        mask_target[:, 0:5, 5:] = 1
+        mask = BitmapMasks(mask_array, 10, 10)
+        mask = mask.translate((20, 8), 5)
+        assert mask.masks.shape == (5, 20, 8)
+        assert_allclose(mask_target, mask.masks)