[Fix] Fix the bug of counting ignore index in IOU in seg_eval (#2229)

* fix seg_eval

* add test for the bug

* update

* update

* update

mmdet3d/evaluation/functional/seg_eval.py

@@ -99,6 +99,9 @@ def seg_eval(gt_labels, seg_preds, label2cat, ignore_index, logger=None):
         hist_list.append(fast_hist(pred_seg, gt_seg, num_classes))
 
     iou = per_class_iou(sum(hist_list))
+    # if ignore_index is in iou, replace it with nan
+    if ignore_index < len(iou):
+        iou[ignore_index] = np.nan
     miou = np.nanmean(iou)
     acc = get_acc(sum(hist_list))
     acc_cls = get_acc_cls(sum(hist_list))

tests/test_evaluation/test_functional/test_seg_eval.py

@@ -11,13 +11,12 @@ def test_indoor_eval():
         pytest.skip()
     seg_preds = [
         np.array([
-            0, 0, 1, 0, 0, 2, 1, 3, 1, 2, 1, 0, 2, 2, 2, 2, 1, 3, 0, 3, 3, 3, 3
+            0, 0, 1, 0, 0, 2, 1, 3, 1, 2, 1, 0, 2, 2, 2, 2, 1, 3, 0, 3, 3, 4, 0
         ])
     ]
     gt_labels = [
         np.array([
-            0, 0, 0, 255, 0, 0, 1, 1, 1, 255, 1, 1, 2, 2, 2, 2, 2, 3, 3, 3, 3,
-            3, 255
+            0, 0, 0, 4, 0, 0, 1, 1, 1, 4, 1, 1, 2, 2, 2, 2, 2, 3, 3, 3, 3, 3, 4
         ])
     ]
 
@@ -26,8 +25,9 @@ def test_indoor_eval():
         1: 'bicycle',
         2: 'motorcycle',
         3: 'truck',
+        4: 'unlabeled'
     }
-    ret_value = seg_eval(gt_labels, seg_preds, label2cat, ignore_index=255)
+    ret_value = seg_eval(gt_labels, seg_preds, label2cat, ignore_index=4)
 
     assert np.isclose(ret_value['car'], 0.428571429)
     assert np.isclose(ret_value['bicycle'], 0.428571429)