If you are using torchvision.transforms, which can be applied to tensors, you could add them to the forward method of your model and script them.
On the other hand, if you are using image transformation, which are applied to PIL.Images, you won’t be able to use them directly in C++ (at least I’m not aware of a way to use PIL in C++) and could use e.g. OpenCV, which is available in Python and C++ for the preprocessing instead.