[Fix] Fix MixUp transform filter boxes failing case. Added test case

mmdet/datasets/pipelines/transforms.py

@@ -2426,9 +2426,8 @@ def _mixup_transform(self, results):
             keep_list = self._filter_box_candidates(retrieve_gt_bboxes.T,
                                                     cp_retrieve_gt_bboxes.T)
 
-            if keep_list.sum() >= 1.0:
-                retrieve_gt_labels = retrieve_gt_labels[keep_list]
-                cp_retrieve_gt_bboxes = cp_retrieve_gt_bboxes[keep_list]
+            retrieve_gt_labels = retrieve_gt_labels[keep_list]
+            cp_retrieve_gt_bboxes = cp_retrieve_gt_bboxes[keep_list]
 
         mixup_gt_bboxes = np.concatenate(
             (results['gt_bboxes'], cp_retrieve_gt_bboxes), axis=0)

tests/test_data/test_pipelines/test_transform/test_transform.py

@@ -967,6 +967,33 @@ def test_mixup():
     assert results['gt_bboxes'].dtype == np.float32
     assert results['gt_bboxes_ignore'].dtype == np.float32
 
+    # test filter bbox :
+    # 2 boxes with sides 1 and 3 are filtered as min_bbox_size=5
+    gt_bboxes = np.array([[0, 0, 1, 1], [0, 0, 3, 3]], dtype=np.float32)
+    results['gt_labels'] = np.ones(gt_bboxes.shape[0], dtype=np.int64)
+    results['gt_bboxes'] = gt_bboxes
+    results['gt_bboxes_ignore'] = np.array([], dtype=np.float32)
+    mixresults = results['mix_results'][0]
+    mixresults['gt_labels'] = copy.deepcopy(results['gt_labels'])
+    mixresults['gt_bboxes'] = copy.deepcopy(results['gt_bboxes'])
+    mixresults['gt_bboxes_ignore'] = copy.deepcopy(results['gt_bboxes_ignore'])
+    transform = dict(
+        type='MixUp',
+        img_scale=(10, 12),
+        ratio_range=(1.5, 1.5),
+        min_bbox_size=5,
+        skip_filter=False)
+    mixup_module = build_from_cfg(transform, PIPELINES)
+
+    results = mixup_module(results)
+
+    assert results['gt_bboxes'].shape[0] == 2
+    assert results['gt_labels'].shape[0] == 2
+    assert results['gt_labels'].shape[0] == results['gt_bboxes'].shape[0]
+    assert results['gt_labels'].dtype == np.int64
+    assert results['gt_bboxes'].dtype == np.float32
+    assert results['gt_bboxes_ignore'].dtype == np.float32
+
 
 def test_photo_metric_distortion():
     img = mmcv.imread(