[bug fix] potential problem if img fed to model is in rectangular shape

utils/datasets.py

@@ -679,8 +679,8 @@ def letterbox(img, new_shape=(640, 640), color=(114, 114, 114), auto=True, scale
         dw, dh = np.mod(dw, 64), np.mod(dh, 64)  # wh padding
     elif scaleFill:  # stretch
         dw, dh = 0.0, 0.0
-        new_unpad = new_shape
-        ratio = new_shape[0] / shape[1], new_shape[1] / shape[0]  # width, height ratios
+        new_unpad = (new_shape[1], new_shape[0])
+        ratio = new_shape[1] / shape[1], new_shape[0] / shape[0]  # width, height ratios
 
     dw /= 2  # divide padding into 2 sides
     dh /= 2