Object Orientated Data

Topic 5: Multimedia Technology

Object Orientated Data Types

• Created on a computer not by sampling real world information

• Details are stored on the attributes (properties) of each object that is stored in the file.

• Each object can be altered by changing its attributes…

Examples• Text

– A character in a text file can be given a different size, colour or font

• MIDI music– A note in a MIDI sound can be given a different

volume, length or pitch

• Drawing – A shape in a drawing can be given a different size or

fill colour

• 3D image– An object in a 3D image can be given a different

location, rotation or texture

Object Orientated Data Files

• All data is stored as a group of objects within a file

• Each object can be edited individually without affecting any others

• All aspects of each object are decided by its properties (attributes)

• These files are basically a collection of objects with details about them. This means they can be stored as plain text files.

Input of Object Orientated Data

Although OOD can be created using nothing but a simple text editor there are specialised input devices to help users create and edit them

• You are already familiar with a keyboard for entering text

Specialised Input Devices

• To create drawings or 3D images a graphics tablet– More accurate than using a

mouse

• To enter musical notes a MIDI keyboard– Easier than using a computer

keyboard

• 3D digitisers can measure points on an object and generate a 3D object from data

Output / Display of OOD

• The quality of object orientated data is very dependant on the hardware & software used to output it.

• For example:– Web browser setting can cause the same text

to be displayed in different ways on different computers

– Different graphics cards for rendering 3D images on screen may produce different quality and support different features

Converting from OOD

OOD How it can be converted Discrete data

2D drawing

Often in ‘Save As’ or ‘Export’ menu of drawing program

Bitmap Image

3D ImageCalled ‘rendering’. Generates a flat (2D) image from a given point of view.

Bitmap Image

TextScanning printed text or doing a ‘screen shot’ and pasting it into bitmap image software

Bitmap Image

Midi music

Often using ‘Save As’ or ‘Export’ function but can also be recorded internally

Digitised Sound file

Object Orientated Data

Topic 5: Multimedia Technology

Recap

• Object Orientated Data– All data is stored as a group of objects within

a file– Details are stored on the attributes

(properties) of each object that is stored in the file.

– Each object can be edited individually without affecting any others

– These files are basically a collection of objects with details about them. This means they can be stored as plain text files.

Vector Graphics data

• A vector is a mathematical term for a line with a specific length and direction.

• A monitor creates the image by drawing rows of dots

• Vector displays use the electron beam to draw out the shapes (no colour)

Vector Vs Bitmap

Scaling causes pixellation. Can be scaled to large sizes, keeping original quality.

Only the image as a whole can be edited.

Individual objects can be edited.

Are very difficult to convert to vector formats

Are easily converted to bitmap formats.

File sizes can be large. File sizes are relatively small.

Images can be very realistic (e.g. digital photograph).

Difficult to create realistic images

Vector Vs BitmapSize of image can be increased keeping quality and file size the same.

Increasing the image size needs re-sampling and increases the file size.

Only individual objects can be edited (it is sometimes impossible to edit only part of the object).

Same appearance in all systems, regardless of hardware or software.

Dependent on output hardware or software for appearance & quality.

Individual pixel level editing is allowed - allowing effects such as spray paint, blur, effects and so on.

Suitable for natural, hand-drawn looking, realistic images.

Suitable for graphic, unrealistic images and designs.

Attributes

• Attributes are the properties that determine what and how objects will appear

Attributes

Object 3

Object 2

Object 4

Object 1

Object 6

Object 5

Object 7

Object Orientated File Formats

Drawing : SVG

3D : VRML/WML

Digitised sound : MIDI

Drawing File Formats

Scalable Vector Graphics (SVG)

• A format for encoding vector graphics in XML (eXtensible Markup Language)

• Designed to provide vector graphic content in Web pages.

• Viewing: – You must have an SVG capable Browser, a

plug-in for your browser or a stand-alone SVG viewer.

3D Image File Formats

Virtual Reality Modelling Language/ World Representation Language (VRML/WRL)

• Standard for describing interactive 3D objects and worlds

• Capable of representing static and animated 3D & multimedia objects with hyperlinks to other media such as text, sounds, movies and images

Synthesised Sound Data (MIDI)

• MIDI is a standard that was created to allow musical instruments to be able to communicate with each other

• A MIDI file consists of Channels (up to 16)• Each channel consists of a sequence of

messages including: – Start of a note– Channel to use– Pitch of the note– Volume to play it at– End of note

Synthesised Sound Data (MIDI)

Attribute Meaning

Instrument Defines instrument being played

PitchSets musical tone of note which is determined by the frequency

Volume Controls loudness/amplitude of note

DurationDetermines length of note (number of beats)

Tempo RateSpeed at which the piece of music is set

Synthesised Sound Data (MIDI)

Advantages• Smaller file size• All aspects of music

can be edited• Effects can be applied

to individual instruments

• There is no interference from the recording

Disadvantages• Never sounds as

realistic as digitised sound

• Dependent on soundcard for quality

• Does not contain vocals

• Fewer effects can be applied to sound