Fix transparency parameter and window size (#68)

Summary:
* Fixed missing alpha in instance masks of panoptic segmentation output
*(When changing alpha in demo/demo.py, the instance masks' alpha doesn't change otherwise)*
* Add namedWindow to handle the overlage window size
Pull Request resolved: #68

Differential Revision: D17926546

Pulled By: ppwwyyxx

fbshipit-source-id: 0ed302c9e6f662bb0bb90d667dbe0cbde8db845e

demo/demo.py

@@ -13,6 +13,9 @@
 
 from predictor import VisualizationDemo
 
+# constants
+WINDOW_NAME = "COCO detections"
+
 
 def setup_cfg(args):
     # load config from file and command-line arguments
@@ -92,14 +95,16 @@ def get_parser():
                     out_filename = args.output
                 visualized_output.save(out_filename)
             else:
-                cv2.imshow("COCO detections", visualized_output.get_image()[:, :, ::-1])
+                cv2.namedWindow(WINDOW_NAME, cv2.WINDOW_NORMAL)
+                cv2.imshow(WINDOW_NAME, visualized_output.get_image()[:, :, ::-1])
                 if cv2.waitKey(0) == 27:
                     break  # esc to quit
     elif args.webcam:
         assert args.input is None, "Cannot have both --input and --webcam!"
         cam = cv2.VideoCapture(0)
         for vis in tqdm.tqdm(demo.run_on_video(cam)):
-            cv2.imshow("COCO detections", vis)
+            cv2.namedWindow(WINDOW_NAME, cv2.WINDOW_NORMAL)
+            cv2.imshow(WINDOW_NAME, vis)
             if cv2.waitKey(1) == 27:
                 break  # esc to quit
         cv2.destroyAllWindows()
@@ -132,6 +137,7 @@ def get_parser():
             if args.output:
                 output_file.write(vis_frame)
             else:
+                cv2.namedWindow(basename, cv2.WINDOW_NORMAL)
                 cv2.imshow(basename, vis_frame)
                 if cv2.waitKey(1) == 27:
                     break  # esc to quit

detectron2/utils/visualizer.py

@@ -447,7 +447,7 @@ def draw_panoptic_seg_predictions(
             colors = [random_color(rgb=True, maximum=1) for k in category_ids]
         except AttributeError:
             colors = None
-        self.overlay_instances(masks=masks, labels=labels, assigned_colors=colors)
+        self.overlay_instances(masks=masks, labels=labels, assigned_colors=colors, alpha=alpha)
 
         return self.output