Download - 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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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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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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Image Compression (4)
Photo image (222x198 pixels) Reduced quality Higher compression JPEG 3KB
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Image Compression (5)
Photo image (222x198 pixels) Very low quality Very high compression JPEG 1KB
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Image Compression (7)
Clipart image (in bitmapped formats 748x543) GIF 19KB JPEG 29KB WMF 83KB BMP 1,190KB
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Image Compression (8)
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 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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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