Digital image processing has become economical in many fields like signature recognition, iris recognition and face recognition, in forensics, in automobile detection and in military applications. Each of these applications has its basic requirements, which may be unique from the others. Everyone is concerned and demands a system as faster, more accurate, cheaper and more extensive computation. This paper has reviewed various image processing operations to illustrate the basic concepts and to use them in different fields with minor changes in the methodology. This paper discusses about the basic technical aspects of digital image processing with reference to be categorized into three groups as: Image Rectification and Restoration, Enhancement and Information Extraction. Importance of digital image processing and its applications are also discussed from the fields of computer vision and other applications. An image is defined as an array, or a matrix, of square pixels arranged in rows and columns. Image processing is a procedure of converting an image into digital form and carry out some operation on it, in order to get an improved image and to retrieve some important information from the image.