Allow detect.py to use video size for initial window size (#8330)

detect.py

@@ -106,7 +106,7 @@ def run(
 
     # Run inference
     model.warmup(imgsz=(1 if pt else bs, 3, *imgsz))  # warmup
-    dt, seen = [0.0, 0.0, 0.0], 0
+    seen, windows, dt = 0, [], [0.0, 0.0, 0.0]
     for path, im, im0s, vid_cap, s in dataset:
         t1 = time_sync()
         im = torch.from_numpy(im).to(device)
@@ -173,7 +173,10 @@ def run(
             # Stream results
             im0 = annotator.result()
             if view_img:
-                cv2.namedWindow(str(p), cv2.WINDOW_NORMAL | cv2.WINDOW_KEEPRATIO)  # allow window resize (Linux)
+                if p not in windows:
+                    windows.append(p)
+                    cv2.namedWindow(str(p), cv2.WINDOW_NORMAL | cv2.WINDOW_KEEPRATIO)  # allow window resize (Linux)
+                    cv2.resizeWindow(str(p), im0.shape[1], im0.shape[0])
                 cv2.imshow(str(p), im0)
                 cv2.waitKey(1)  # 1 millisecond