This book systematically introduces the basic concepts and theories, methodologies and algorithms of digital image processing, which is divided into 12 chapters and three parts. Part 1 presents the general knowledge about digital image processing, including the basic concepts and backgrounds of the subject. Part 2 as the core content of the book systematically discusses the basic technologies of digital image processing, including various transformations, basic operations, image domain enhancement, image frequency domain enhancement, color image processing, image restoration and image coding. Part 3 is unfolded around image analysis and image understanding, introducing the ideas about image segmentation, mathematical morphology, image characteristics and image understanding. This book can be used as an image processing textbook for senior undergraduate and graduate students majoring in electronic information engineering and other relevant majors.