autoShape forward im = np.asarray(im) # to numpy (ultralytics#2689)

Slight speedup.

(cherry picked from commit 17300a4)

models/common.py

@@ -258,7 +258,8 @@ def forward(self, imgs, size=640, augment=False, profile=False):
                 im, f = Image.open(requests.get(im, stream=True).raw if im.startswith('http') else im), im  # open
                 im.filename = f  # for uri
             files.append(Path(im.filename).with_suffix('.jpg').name if isinstance(im, Image.Image) else f'image{i}.jpg')
-            im = np.array(im)  # to numpy
+            if not isinstance(im, np.ndarray):
+                im = np.asarray(im)  # to numpy
             if im.shape[0] < 5:  # image in CHW
                 im = im.transpose((1, 2, 0))  # reverse dataloader .transpose(2, 0, 1)
             im = im[:, :, :3] if im.ndim == 3 else np.tile(im[:, :, None], 3)  # enforce 3ch input