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Web Image Basics

Web Image Basics

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Web Image Basics

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  1. Web Image Basics Comp 140 December 2

  2. Vector Graphics • Can be repositioned or resized • Will not diminish output quality • Typically stored in AI, EPS, PICT or WMF formats • Only SVG is supported by browsers • Check out www.w3cschools.com/svg

  3. Raster Graphics • Used primarily by web designers • Built from pixels (picture elements) • Perfectly square • All same size • Display only one color at a time

  4. Resolution • Expression of image quality measured in the number of pixels that fit in one inch (ppi) • Don’t have to be above 72 ppi • At least 300 ppi for printing • Size • The larger the image, the more pixels needed • Full size images for web pages not found too often

  5. Color • Monochrome • 1 bit color • Black or white • 4 bit color • Upto 16 colors • Dithering intersperses and juxtoposes available color to create an illusion of more color • 8 bit color uses upto 256 colors or 256 shades of gray • Websafe colors included • 16 bit - 65,000 colors • 24 bit – 16.7 million colors • ?

  6. Raster Images • JPG, GIF, PNG • GIF (Graphical Interchange Format) • 256 colors • 72 ppi • JPEG ( Joint Photographic Experts Group) • Famous for its patented selectable image compression algorithm • May damage image quality • PNG (portable network graphic) • Supports unlimited resolution, 32 bit color and full alpha and index transparency • Alpha transparency less of a concern as newer browsers can handle it