Graphics and Multimedia Foundation Computing The beatings will continue until morale improves

Graphics and Multimedia

Foundation Computing

The beatings will continue until morale improves.

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What is Multimedia?Literally, the combination of two or more

types of media or effects: text graphics photographs sound video animation

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Uses of Multimedia Marketing Education & Training Computer Aided Design (CAD) Desktop Publishing Games Movie Making Virtual Reality

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Uses of GraphicsDiagramsGraphs and Charts, eg. ExcelClip ArtPhotographsThe graphical user interface of Windows,

eg. icons, menus, etc.

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Monitors, Printers & Pixels In order to see graphics on a screen or printer it

must be represented as lots of dots – PIXELS A computer screen in made up of lots of pixels,

perhaps 800 600 or 1024 768 A printer also assembles a printed page as lots of

dots, perhaps 600 dpi for a good laser printer

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How Much Memory? Say we want to store a photograph to go as our

screen background Perhaps 800 600 pixels Perhaps 24 bit colour, ie. about 16 million colours,

requires 3 bytes per pixel The complete uncompressed image file requires

800 600 3 bytes = 1.44 Mb (same as a complete floppy disk)

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Bitmapped Graphics If we store every pixel of a graphical image, we

call this a bitmap Stored in Windows BMP files and other

compressed formats, eg. JPEG & GIF files Can be black & white, greyscale or full colour (8,

16 or 24 bits per pixel) Also known as raster graphics

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How to Generate Bitmaps?A scannerA digital cameraA screen dump, eg. PrintScreenA PAINT program, eg. Windows PaintA photographic editing program, eg.

Microsoft Photo Editor or Adobe PhotoShop

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Shortcoming of Bitmaps They take up a lot of memory! Difficult to edit because there is no structure, just

a whole lot of pixels Difficult to enlarge without the jagged edges of

the pixels becoming visible

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Bitmaps

100% 200% 400% 800%

Bitmap -enlarged

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Vector Graphics The alternative to bitmaps is to store the structure

of a diagram as objects, eg. lines, circles, arrows and other shapes

Each object within the diagram can have characteristics such as line width and colour, fill colour and shading etc

A complete diagram is a collection of graphical objects

A rendering program takes the vector graphic description and converts to a bitmap at a specific size

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How to Generate Vector Graphics?

Must create manually using a DRAWING program

Examples: MS Office has a built-in set of drawing tools

that are common to programs like Word and PowerPoint

Engineering and Architectural CAD (computer aided design) programs

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Advantages of Vector Graphics Can take up less memory because don't have to

store individual pixels Individual objects within a complete vector

graphic diagram can be edited, removed etc. Vector graphic objects and diagrams can be

resized without any distortion or jagged edges appearing

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Vector Graphics

100% 200% 400% 800%

Vector graphic – enlarged

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Disadvantages of Vector Graphics No standard interchange format - every software

program has its own format! SVG (Simple Vector Graphics) from W3C is an

emerging open standard Windows uses Windows Metafiles (.WMF) but

these are often embedded inside a Word or PowerPoint file

Cannot store scanned images or photographs as vector graphics.

Limited capability for artistic drawing

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Graphics on the InternetThe widespread use of graphics on the

World Wide Web has led to a number of common COMPRESSED graphics formats

The three most common, supported by all Web Browsers, are: GIF (Graphics Interchange Format) JPEG (Joint Photographic Encoding Group) PNG (Portable Network Graphics)

All are bitmap formats

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Table Based Table of colours in image Each pixel has index to table Example: GIF

(256 colour limit) Good for simple images

like icons

Image Compression

12345678

2 1

3 6

4 5

7 7

8 3

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Image Compression (2)

Lossy Compression Similarity of neighbouring pixels stored How much info and how far quality Example: JPEG Good for photographs

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Photo image (222x198 pixels) JPEG 7KB GIF 84KB BMP 128KB WMF 128KB

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Photo image (222x198 pixels) Reduced quality Higher compression JPEG 3KB

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Photo image (222x198 pixels) Very low quality Very high compression JPEG 1KB

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PNG version of JPEG image 84 kbytes!! vs 7 kbytes for

JPEG

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Clipart image (in bitmapped formats 748x543) GIF 19KB JPEG 29KB WMF 83KB BMP 1,190KB

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A drawing (in bitmapped formats 548x499 pixels) WMF 3KB GIF 3KB JPEG 6KB BMP 268KB

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JPEG versus GIF/PNGFormat GIF JPG PNG

Colour Table Yes No No

Colours 256 16 million 16 million

Transparency Yes No Yes

Animation Yes No No

Lossy No Yes No

Good for Simple Diagrams

Photos or artwork

Complex Diagrams

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Generating GIF/JPEG/PNG filesUse SAVE AS functionality of most graphics

programs, eg. Microsoft Paint and Microsoft Office Picture Manager

With GIF select greyscale or 256 colourWith JPEG select greyscale or 24 bit colour,

and also select quality. Lower quality more compression smaller file

See Study Book for example of file sizes

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SoundSound is a vibration of the air, or more

precisely, a variation in air pressureIt is an analogue quantity (continuously

varying)To store on a computer it must be digitisedAt regular intervals the pressure (usually in

the form of a voltage from a microphone) is sampled

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Sound Digitisation (Pulse Code Modulation, PCM)

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Sound FormatsUncompressed PCM formats:

Microsoft Wave Format (.WAV files) Microsoft Resource Interchange File Format

(.RIFF)

Compressed PCM formats: Window Media Audio (.WMA files) The audio side of MPEG-1 Video (.MP3 files) Ogg Vorbis - open and patent free

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Sound Formats (2)Other formats:

Musical Instrument Digital Interface (.MIDI files) designed for music

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Sound Formats (3)MP3 players can often also play .WAV filesMP3 format much smaller than WAV, can

be 1/10 of size CD can hold 700MB, or 74 minutes of

uncompressed audio In MP3 format, CD of the same size can easily

hold 740 minutes of audio!!!

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Sound Formats (4)Play audio on computer using Windows

Media Player, or download software from the Web, eg MusicMatch Jukebox

May be able to convert between formats Often cannot hear difference between

MP3, WAV

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Audacity

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Sound Formats (4)Play audio on computer using Windows

Media Player, or download software from the Web, eg MusicMatch Jukebox

May be able to convert between formats Often cannot hear difference between

MP3, WAV

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Animation, Video and MoviesMany formats supported by various

programs: Moving Picture Experts Group (.MPG

MPEG-1 for Video CDs, output quality similar to VCR quality

MPEG-2 for commercial DVD moviesMPEG-1 is playable by MPEG-2 players

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Animation, Video and Movies (2) Microsoft Audio Visual Interleave (.AVI files)

DV uncompressedDivX compressionXvid compressionMany more …

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Animation, Video and Movies (3) Apple Quicktime Moving Pictures (.MOV) Windows Movie File (.WMV files) Macromedia Flash (.FLA or .SWF) usually used

with a Web browser plugin animated GIF (no audio)

Streaming vs download

These four are commonly used for web delivery

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Animation, Video and Movies (4)Movie compression: each frame is an

image, can compress, can also store changes from one frame to the next only

Documents

Graphics and Multimedia Foundation Computing The beatings will continue until morale improves