Digital Image Processing
The digital image processing deals with developing a digital system that performs operations on an digital image.
What is an Image?
An image is nothing more than a two dimensional signal. It is defined by the mathematical function f(x,y) where x and y are the two co-ordinates horizontally and vertically.
The value of f(x,y) at any point is gives the pixel value at that point of an image.

The figure is an example of digital image. This image is nothing but a two dimensional array of numbers ranging between 0 and 255.

Each number represents the value of the function f(x,y) at any point. In this case the value 128 , 230 ,123 each represents an individual pixel value. The dimensions of the picture is actually the dimensions of this two dimensional array.
Relationship between digital image and signal
If the image is a two dimensional array then what does it have to do with a signal?  
Since anything that conveys information or broadcast a message in physical world between two observers is a signal. That includes speech or (human voice) or an image as a signal. Since when we speak , our voice is converted to a sound wave/signal and transformed with respect to the time to person we are speaking to. Not only this , but the way a digital camera works, as while acquiring an image from a digital camera involves transfer of a signal from one part of the system to the other.
How a digital image is formed?
Since capturing an image from a camera is a physical process. The sunlight is used as a source of energy. A sensor array is used for the acquisition of the image. So when the sunlight falls upon the object, then the amount of light reflected by that object is sensed by the sensors, and a continuous voltage signal is generated by the amount of sensed data. In order to create a digital image , we need to convert this data into a digital form. This involves sampling and quantization. The result of sampling and quantization results in an two dimensional array or matrix of numbers which are nothing but a digital image.
Applications:
Some of the major fields in which digital image processing is widely used are mentioned below:
UV imaging
One particular application of digital image processing in the field of remote sensing is to detect infrastructure damages caused by an earthquake. An image of the effected area is captured from the above ground and then it is analyzed to detect the various types of damage done by the earthquake.

The key steps include in the analysis are

• The extraction of edges
• Analysis and enhancement of various types of edges

Line follower robots.
Most of the robots today work by following the line and thus are called line follower robots. This help a robot to move on its path and perform some tasks. This has also been achieved through image processing.
 
Other applications include;

• Image sharpening and restoration
• Medical field
• Remote sensing
• Transmission and encoding
• Machine/Robot vision
• Color processing
• Pattern recognition
• Video processing
• Microscopic Imaging &
• Others