Most people dislike going through pages of text specially on a computer screen so developers supplement words with pictures
Pictures impart large amount of information in a compact way
The pictures that we see in our everyday life can be broadly classified into two groups:
An Image is a picture that depict some real world situation typically captured by a camera.An image can be Continuous Tone, Half-Tone or Bitone. Graphics implies a synthetic pictorial representation.Graphics can be categorized into Raster Graphic and Vector Graphic.
In sampling input analog value must be held constant during conversion process to avoid inconsistencies due to changeing values.This operation is called SAMPLE-AND-HOLD ,which holds the current sample value constant until the next sample is obtained.
This constant value gives the sampled output its characteristic staircase look.
The output of the set of sampling step is a set of sample values, which represents the changing analog signal.
The next step is to represent values as numbers.
Quantization Level refers to the number of different sample values that can be used to represent a digital quantity.
Since sampling values represent the amplitudes of the analog waves at different time instants, the process of selecting a few number of amplitude levels from a large set is know as Amplitude-Discretization.