"A Key to Image Enhancement" is a comprehensive guide that deals with digital image processing, a dynamic and rapidly evolving field of computer science. The book addresses the challenges associated with image quality, particularly the disturbances that can occur during capture, transmission, or processing. It provides deep insights into various image enhancement techniques aimed at extracting useful information from images. Notably, it emphasizes two novel filters that go beyond conventional methods and are specifically designed to improve old images. This work is aimed at professionals and students who wish to gain a better understanding of image enhancement techniques and seek practical approaches to applying these techniques.