This document discusses various techniques for image denoising. It begins by defining different types of noise that can affect images, such as Gaussian noise, salt and pepper noise, and quantization noise. It then describes several denoising techniques, including linear filters like mean filters and non-linear filters like median filters. Adaptive filters are also discussed as being more selective than linear filters in preserving edges and high-frequency image components. The document concludes that no single denoising method works best for all images and that hybrid approaches combining multiple techniques may produce better results.