add some training fns

dalle2_pytorch/train.py

@@ -2,6 +2,15 @@ import copy
 import torch
 from torch import nn
 
+# image related normalizations
+# ddpms expect images to be in the range of -1 to 1
+
+def normalize_img(img):
+    return img * 2 - 1
+
+def unnormalize_img(normed_img):
+    return (normed_img + 1) * 0.5
+
 # exponential moving average wrapper
 
 class EMA(nn.Module):