Fix bug in segmentation postprocessing (#20198)

* Fix post_process_instance_segmentation
* Add test for label fusing

src/transformers/models/maskformer/image_processing_maskformer.py

@@ -1050,12 +1050,13 @@ class MaskFormerImageProcessor(BaseImageProcessor):
             # Get segmentation map and segment information of batch item
             target_size = target_sizes[i] if target_sizes is not None else None
             segmentation, segments = compute_segments(
-                mask_probs_item,
-                pred_scores_item,
-                pred_labels_item,
-                mask_threshold,
-                overlap_mask_area_threshold,
-                target_size,
+                mask_probs=mask_probs_item,
+                pred_scores=pred_scores_item,
+                pred_labels=pred_labels_item,
+                mask_threshold=mask_threshold,
+                overlap_mask_area_threshold=overlap_mask_area_threshold,
+                label_ids_to_fuse=[],
+                target_size=target_size,
             )
 
             # Return segmentation map in run-length encoding (RLE) format
@@ -1143,13 +1144,13 @@ class MaskFormerImageProcessor(BaseImageProcessor):
             # Get segmentation map and segment information of batch item
             target_size = target_sizes[i] if target_sizes is not None else None
             segmentation, segments = compute_segments(
-                mask_probs_item,
-                pred_scores_item,
-                pred_labels_item,
-                mask_threshold,
-                overlap_mask_area_threshold,
-                label_ids_to_fuse,
-                target_size,
+                mask_probs=mask_probs_item,
+                pred_scores=pred_scores_item,
+                pred_labels=pred_labels_item,
+                mask_threshold=mask_threshold,
+                overlap_mask_area_threshold=overlap_mask_area_threshold,
+                label_ids_to_fuse=label_ids_to_fuse,
+                target_size=target_size,
             )
 
             results.append({"segmentation": segmentation, "segments_info": segments})

tests/models/maskformer/test_feature_extraction_maskformer.py

@@ -589,3 +589,30 @@ class MaskFormerFeatureExtractionTest(FeatureExtractionSavingTestMixin, unittest
             self.assertEqual(
                 el["segmentation"].shape, (self.feature_extract_tester.height, self.feature_extract_tester.width)
             )
+
+    def test_post_process_label_fusing(self):
+        feature_extractor = self.feature_extraction_class(num_labels=self.feature_extract_tester.num_classes)
+        outputs = self.feature_extract_tester.get_fake_maskformer_outputs()
+
+        segmentation = feature_extractor.post_process_panoptic_segmentation(
+            outputs, threshold=0, mask_threshold=0, overlap_mask_area_threshold=0
+        )
+        unfused_segments = [el["segments_info"] for el in segmentation]
+
+        fused_segmentation = feature_extractor.post_process_panoptic_segmentation(
+            outputs, threshold=0, mask_threshold=0, overlap_mask_area_threshold=0, label_ids_to_fuse={1}
+        )
+        fused_segments = [el["segments_info"] for el in fused_segmentation]
+
+        for el_unfused, el_fused in zip(unfused_segments, fused_segments):
+            if len(el_unfused) == 0:
+                self.assertEqual(len(el_unfused), len(el_fused))
+                continue
+
+            # Get number of segments to be fused
+            fuse_targets = [1 for el in el_unfused if el["label_id"] in {1}]
+            num_to_fuse = 0 if len(fuse_targets) == 0 else sum(fuse_targets) - 1
+            # Expected number of segments after fusing
+            expected_num_segments = max([el["id"] for el in el_unfused]) - num_to_fuse
+            num_segments_fused = max([el["id"] for el in el_fused])
+            self.assertEqual(num_segments_fused, expected_num_segments)