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Web Graphics

Web Graphics. By Chris Harding. Contents. Software Vector Graphics and Pixel Based Transparent Images Compression GIF vs. JPEG Animated GIF. Software . Fireworks (Part of Macromedia Suite) Photoshop Paint Shop Pro Microsoft Paint. Web Graphics. Should be kept small. Around 100K mark

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Web Graphics

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  1. Web Graphics By Chris Harding

  2. Contents • Software • Vector Graphics and Pixel Based • Transparent Images • Compression • GIF vs. JPEG • Animated GIF

  3. Software • Fireworks (Part of Macromedia Suite) • Photoshop • Paint Shop Pro • Microsoft Paint

  4. Web Graphics • Should be kept small. Around 100K mark • Large graphics take time to download • Lots of small graphics can make a sight look good • But cause long page loading times

  5. Types of Web Graphics • BMP • PNG • JPEG • GIF

  6. Vector Graphics/Pixel • Vector: • Mathematical formula • Smooth edges • Bitmap/Rasterised: • Pixelated

  7. Transparent Image • Can be JPEG or GIF • Best done with GIF • Can select one colour to be transparent or background • Best results make Background one colour (like pink!) • Select background for transparent layer

  8. Compression • Compacting information • Lossless • Lossy • Lossless • All information retained • Lossy • Information is lost

  9. Compression: Lossless (1/3) • Selected information is retained • Example: • aabbbccdddddee • 2a3b2c5d2e

  10. Compression: Lossless (2/3) • PSD: 6.9 MB • BMP: 1.37 MB

  11. Compression: Lossless (3/3) • GIF: 86KB

  12. Compression: Lossy (1/2) • Image information • Entropy – data kept • Redundancy – data removed

  13. Compression: Lossy (2/2) • Original: 453KB • JPEG: 4KB

  14. Compression Methods • RLE (Run Length Encoding) • Lossless: common Windows file formats. • LZW (Lemple-Zif-Welch) • Lossless: TIFF, PDF, GIF, and PostScript. • Most useful for large areas of single color. • JPEG (Joint Photographic Experts Group) • Lossy: JPEG, TIFF, PDF and PostScript. • Continuous-tone images ie photographs • ZIP • Lossless: PDF and TIFF. • Most effective for large areas of single color.

  15. File>Save as... what?! (1/2) Original 2.9 MBs JPEG 275 KBs GIF 161KBs

  16. File>Save as... what?! (2/2) Original 372 KBs JPEG 13 KBs GIF 7KBs

  17. Animated GIF • Number of different frames • Saved in one file (can be very large) • Play once or looped http://www.webreference.com/dev/gifanim/

  18. Animated GIF • Made up of 7 frames • 4 frames below • Looped file

  19. Web Graphics with CSS • Use CSS with images to create visual effects • Add round border to tables • Roll over images • Menu items • Practical tutorial on this topic next week

  20. Summary • Software • Vector Graphics and Pixel Based • Compression • Lossless • Lossy • GIF vs. JPEG for different uses • Introduce Animated GIF

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