The Text, Images and Video Basic Characteristics

by Gina Tina on April 24, 2013

Some simple application and networking terminology – Text, Images and Video

The essential of a text document, there are three types of text that are used to produce pages of documents:-

  • Un-formatted text – This is known also as plain text and enables pages to be created which comprise strings of fixed-sized characters from a limited character set.
  • Formatted text – This is known also as rich text and enables pages and complete documents to be created that are comprised of strings of characters of different styles, size and shape with tables, graphics and images inserted at appropriate points.
  • Hypertext – This enables Web pages to be created in the form of an integrated set of documents (each comprising formatted text) with defined linkages between them.

 

The essential of an image document there are two types of images:

  • Computer-generated images – This is more generally referred to as computer graphics or simply graphics.
  • Digitized images – These include digitized documents and digitized pictures or photos

Ultimately, both types of image are displayed and printed in the form of a two-dimensional matrix of individual picture element known as pixels. In the case of continuous-tone monochromatic images – such as a printed picture or scene – good quality black and white pictures can be obtained with 8bits per pixel – that is, 256 levels of grey. For colour images, each pixel may contain 8, 16, 24 or more bits to produce a good range of colours. Typical screen sizes are 640×480(VGA) and 1024×768(SVGA). With 8 bits per pixel the VGA format requires 307.3 kbytes to store an image and with 24 bits per pixel the SVGA format requires 2.359296 Mbytes.

How’s about Video?

Most video cameras now operate digitally and generate a sequence of digitized images, each of which is called a frame. With broadcast television, however, the video signal is in an analogue form and hence the source video signal must first be converted into a digital form. To do this, there are a number of what are called digitization formats used, each of which is targeted at a particular screen size. Then, to obtain a moving picture, the frames are stored and played out at rate determined by the digitization format that is used. For example, the raw bit rate of television is 162 Mbps and that for a small screen picture phone is 40 Mbps.

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