An Introduction to Computer Graphics B.Sc. (Hons) Multimedia ComputingMedia Technologies

An Introduction toComputer Graphics

B.Sc. (Hons) Multimedia Computing

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Agenda

Image Acquisition Vector Graphics Bitmapped Graphics Layers File Formats Optimisation and Deployment Software


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Image Acquisition


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Scanner Digital Camera Computer Artwork Digital Capture or Transfer Library Material

Image Quality: Scanners

Optical Resolution – determined by the number of Charge Coupled Devices (CCDS)

Mechanical Resolution – distance scanner travels each time to take a vertical snapshot of the image

Interpolation between snapshots Mechanical construction may affect mechanical

resolution Integrated or dedicated flatbed


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Types of Scanners

Flatbed Integrated ‘all in one’i.e scanner, printer, copier


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Different Scanners give different images

Microtech Flatbed

Dell ‘all in one’i.e scanner, printer, copier

Dell Scanner

Microtech Scanner

Image Quality: Digital Cameras

Conventional ‘enprint’ from a 35mm negative has the equivalent of some four million pixels worth of picture information.

Digital camera therefore requires at least 4 Megapixels to equal 35mm resolution.

Nikon and Canon manufacture high-end (pricey) 35mm DSLRs

‘Professional’ cameras (medium format ) use 6cm x 6cm negatives. -


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Digital Cameras : Nikon D3 (12 Mega Pixels)

First Full-frame Nikon DSLR (October 2007)


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Digital Cameras : Pentax Optio (5 Mega Pixels)


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Vector Graphics Mathematically prescribed Wont loose resolution when scaled Give very lightweight file sizes Limited picture information for photorealism File Formats .wmf, .swf, cgm Software

Adobe Illustrator, Adobe Freehand Bitmap and Vector editing features in Flash and

Fireworks


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Bitmapped Graphics

Allow for high-definition photorealistic images. Image encoded on a pixel by pixel basis. Image resolution degraded when scaled Supports lossless compressions algorithms File Formats - .BMP, .GIF, .JPG, .TIF .TGA Software

Adobe Photoshop ( with ImageReady) Macromedia Fireworks PaintShop Pro (Shareware)


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GIF = Graphics Interchange Format

2 – 256 colours compressed before stored Lossless compression algorithm Two common types GIF87a and GIF89a GIF89a

Supports transparency Supports animation sequence

License issues if supported in a graphics software package


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GIF 256 : 800 x 600 : 256 Colours: File Size 164KB

JPEG = Joint Photographic Experts Group

Specifically designed for photographic images.

Supports up to 24 bits per pixel Lossy compression algorithm Image quality chose when exported

from graphics Quality versus file size


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JPEG : 800 x 600 : 80 % : File Size 71KB


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JPEG : 800 x 600 : 60 % : File Size 37 KB


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JPEG : 800 x 600 : 30 % : File Size 12 KB

GIF or JPEG ?

To which format should you export your images? The general rule is if the image was created with a

computer package from scratch - then save as a GIF If the image is of a real picture - scanned or from a

digital camera - save as a JPEG


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Layers and Construction Files

Layers control accessibility and aid workflow Lock layers Hide layers Use mask layers for visual effect

Layers are provide recipe file for future editing and revisions

Layers are lost (flattened) when the image is exported to a given bitmap file format

Construction file has lost of information so has a very large file size compared to exported image format


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Optimisation & Deployment

Control over compression (.JPEG) Palette depth (.GIF) Balance of picture quality versus file size For web deployment use ‘Export for web’ Never deploy the construction (layered) file! Deploy for non-BroadBand audiences (for now)


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Documents

An Introduction to Computer Graphics B.Sc. (Hons) Multimedia ComputingMedia Technologies