The proper processing of the images of cytology is essential to implement computational cytology. Image processing includes image acquisition, pre-processing, segmentation and feature extraction. Noise reduction is an important part of image pre-processing. It can be done by spatial domain filtering, frequency domain filtering, wavelet-based denoising and deep learning-based approaches. Stain normalization and artefact removal are also important. The section or smear often needs annotation to highlight the region or cells of interest. In the present chapter, the various steps of image processing have been discussed.