Comp Sci - Lecture 3.docx

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Western University
Computer Science
Computer Science 1033A/B
Vivi Tryphonopolous

Lecture 3 What is digitization? • Refersto the processof translating a piece of information into bits • Bits= binary digits Fundamentalunits of information in a computer system ("0" and "1") Electric signalstranslate into "bits" ("0" and "1") • 1 Byte= 8 bits x bits=# of digits,y values=# of combinations ex:2 4 {4 bit )= 16 values,:. x=4,y=16 • an image is represented by a grid (array,matrix) of squarescalled pixels (Picture Elements) • pixel= the smallest image component D:. shows smallest detail • arranged in columns and rows • eachpixel is given a numerical value that represents the corresponding colour Colour Coding • range of colours D associatedwith number of bits • if a pixel colour is represented by 1bit only {O=black,1=white) D:. 1bit allows for 2colours • Rule:more bits=more shades{colours) • In true colour each pixel represents same colour shade Colour Models • UsedforWeb: o Additive model (RGB) Primary colours= red,green,blue Adding light to black background (monitor) in order to obtain colour shades • Used for Printing: o Subtractive model (CYMK) Cyan,magenta ,yellow Ink when applied removes ("subtracts") from a white background RGBCode • Eachpixel is represented by three values (R,G,B) • Syntax Eachvalue ranges from 0-255 0 = no colour,255 = max amount 8 256 colour shades =1 bits Need 3 bytes for true colour (8 bits= 1 byte) RGBCode:<0-255,0-255,Q-255> {black= <0,0,0> ,white = <255,255,255> ) • The human eye can detect about 10 million colours Types of Graphics • Affects how the graphics are displayed on a computer screen: 1. Quality 2. File Size 3. Time to display graphics Bitmap Graphics • Also known as RASTERgraphics • Made up of pixels • Editing pixels= changing colour,shade and brightness • If you start with a small image & make it larger by resizing... squares become larger,edges more jagged ] -- quality decreases pixelation file size increases Vector Graphics • Image represented with lines and arcs that have a mathematical relationship which describes the drawing of the shape • It doesn't matter what size the image is • Asthe image is resized larger/smalle r... Edgesstill clean,crisp No distortion going up/down in size Quality is maintained File size increases {if resized larger) Graphic Software 1. Vector Based Geared towards drawings Greater control and precision
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