Digital image processing deals with manipulation of digital images through a digital computer. It is a subfield of signals
and systems but focus particularly on images. DIP focuses on developing a computer system that is able to perform processing on an image.
The input of that system is a digital image and the system process that image using efficient algorithms, and gives an image as an output.
The most common example is Adobe Photoshop. It is one of the widely used application for processing digital images.
Since DIP is a subfield of signals and systems , so it would be good if you already have some knowledge about signals and systems , but it is not necessary. But you must have some basic concepts of digital electronics.
Basic understanding of calculus , probability and differential equations is also required for better understanding.