fix preprocessing

apps/ios_rpc/tests/ios_rpc_mobilenet.py

@@ -50,6 +50,8 @@ def compile_metal(src, target):
 
 
 def prepare_input():
+    from torchvision import transforms
+
     img_url = "https://github.com/dmlc/mxnet.js/blob/main/data/cat.png?raw=true"
     img_name = "cat.png"
     synset_url = "".join(
@@ -65,13 +67,19 @@ def prepare_input():
     synset_path = download_testdata(synset_url, synset_name, module="data")
     with open(synset_path) as f:
         synset = eval(f.read())
-        image = Image.open(img_path).resize((224, 224))
+        input_image = Image.open(img_path)
 
-    image = np.array(image) - np.array([123.0, 117.0, 104.0])
-    image /= np.array([58.395, 57.12, 57.375])
-    image = image.transpose((2, 0, 1))
-    image = image[np.newaxis, :]
-    return image.astype("float32"), synset
+    preprocess = transforms.Compose(
+        [
+            transforms.Resize(256),
+            transforms.CenterCrop(224),
+            transforms.ToTensor(),
+            transforms.Normalize(mean=[0.485, 0.456, 0.406], std=[0.229, 0.224, 0.225]),
+        ]
+    )
+    input_tensor = preprocess(input_image)
+    input_batch = input_tensor.unsqueeze(0)
+    return input_batch.detach().cpu().numpy(), synset
 
 
 def get_model(model_name, data_shape):