# Preprocessing API

Raw CCD frames to preprocessed images (IM files): bias/dark subtraction, variance initialisation, bad-pixel masking, and cosmic-ray removal. See the [IM stage theory](../explanations/isoplane-theory.md) for background.

```{eval-rst}
.. automodule:: kspecdr.preproc.make_im
   :members:

.. automodule:: kspecdr.preproc.preproc
   :members:
```