# Object and Image

Object and image are common terms in computer graphics.

Objects are real-world entities representing actual things. Objects may be natural like flowers, clouds, mountains, trees etc. or they may be artificial like a car, cell phone, book, ball etc. Objects are represented using a three-dimensional coordinate system. Computer graphics deals with mapping real-world objects to the computer screen.

The representation of real-world objects on the digital display device is known as an image. Objects in the real world are continuous in nature, they have a smooth boundary. When they are mapped on a monitor screen, they are discretized and often they have zigzag boundaries due to the grid structure of the monitor screen.

Formally, an Image is a two-dimensional array of pixels. A pixel is the smallest addressable unit of an image. Mathematically, an image is defined as a function of its spatial coordinates (x, y). Where (x, y) defines the position of the pixel in the image and function f(x, y) represents the intensity or colour at that position. The Figure shows how the continuous shapes are converted to discrete entities while converted into digital images or mapped on the monitor screen.

As we can see in the figure, the shape is rasterized by selecting the pixels on the screen in which the object is passing through and the interior region.