CH11 Graphics Notes

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CH11 Graphics Notes

  1. 1. © 2004 Ken Baldauf, All rights reserved. Graphics CGS2826 Web Design Program in Interdisciplinary Computing Florida State University From Web Style Guide, Chapter 11: Graphics
  2. 2. © 2010 Ken Baldauf, All rights reserved. What are the most effective uses of graphics, and what’s the best way to integrate words and images into an understandable story for the user?
  3. 3. © 2010 Ken Baldauf, All rights reserved. Roles of Web Graphics  Define site boundaries  Provide and enhance content: illustrations, diagrams, charts, visualizations, word art
  4. 4. © 2010 Ken Baldauf, All rights reserved.
  5. 5. © 2010 Ken Baldauf, All rights reserved. Characteristics of Web Graphics  RGB model is called “additive” because a combination of the three pure colors—red, green, and blue—“adds up” to white light.  16.8 million colors that are theoretically possible in a 24-bit or 32-bit display screen.  72 to 96 pixels per inch (ppi)
  6. 6. © 2010 Ken Baldauf, All rights reserved. Gamma The degree of contrast between the midlevel gray values of an image.
  7. 7. © 2010 Ken Baldauf, All rights reserved. Graphics and Bandwidth  Some web users access the Internet via modem, slow wireless connection, or cell phone network, and others view pages on the small display of a handheld device such as a cell phone or an iPod Touch. This reality imposes limits on the file size and physical dimensions of web graphics.
  8. 8. © 2010 Ken Baldauf, All rights reserved. Graphics File Formats  GIF – 8 bit, 256 colors  Compression: lossless, ideal for logos  Dithering: reducing color amnt to 256  Interlaced: loads entire image from low to high rez  Transparent: select background color as trans  JPEG – 24 bit, 16.8 million colors  Great for photos  PNG  Combines best of GIF and JPEG but may lack support
  9. 9. © 2010 Ken Baldauf, All rights reserved. GIF Dithering
  10. 10. © 2010 Ken Baldauf, All rights reserved.
  11. 11. © 2010 Ken Baldauf, All rights reserved. Advantages of GIF files •gif is the most widely supported graphics format on the web •gifs of diagrammatic images look better than jpegs •gif supports transparency and interlacing Advantages of JPEG images •jpeg achieves huge compression ratios, which mean faster downloads •jpeg produces excellent results for most photographs and complex images •jpeg supports full-color (24-bit, true-color) images
  12. 12. © 2010 Ken Baldauf, All rights reserved. Display vs. Print Four-color printed images are separated into four subtractive printing colors (cyan, magenta, yellow, and black).
  13. 13. © 2010 Ken Baldauf, All rights reserved. Display vs. Print
  14. 14. © 2010 Ken Baldauf, All rights reserved. Coding graphics  Include height and width specs for faster loading pages  Include “alt” as a fall back <img src="up.gif" height="10" width="10" alt="Go to top of page">
  15. 15. © 2010 Ken Baldauf, All rights reserved. Color Combos http://www.colorsontheweb.com/colorcontrast.asp
  16. 16. © 2010 Ken Baldauf, All rights reserved. Harmonious Combos

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