These are notes from a presentation Kristin A. Antelman gave during ALA Mid-winter's meeting, February, 1997

Resolution:

• computers display 72 dpi (dots per inch)
• don't scan higher unless you intend the image to be printed

Color Depth (i.e., the number of colors represented in an image)

• 256 colors (8 bit graphics) is usually sufficient
• photos and exhibit images should be scanned at thousands or millions of colors
• reducing (indexing) to 7 bits (128) will decrease quality somewhat but file size significantly

Users and Access

• who is your primary audience and what hardware do they have?
• what is the speed of the network?
• is your site accessed by many dial-up users?

Navigation of your Website

• do your graphics aid novice users in navigating your site?
• do your graphics have a clear meaning?
• is their use consistent across your webpages?

Key Concepts

• File size
  • dimensions in inches or pixels
  • bytes of memory
• File formats
  • gif and jpeg are the most commonly used graphics formats
  • use gif for drawings, logos, icons, and screen capture
  • use jpeg for continuous tone images, such as photos

Icons

• try to avoid editing icons: they do not scale up or down well
• try to create unique icons instead of using same old web icons everyone else uses
• icons should be transparent (GIF89a)

Banner Logo

• save as interlaced GIF (interlaced JPEG not yet widely supported)
• image should be no wider than 470 pixels

Scanned Images

• informational images
  • small is important
  • if JPEG, save at medium or high resloution
  • reduce to 256 colors
• exhibit or archival images
  • produce high quality images in multiple sizes, including 72-dpi for display
  • use thumbnails to preview multiple images on a page

Buttons

• consider a simple imagemap or table with color background and plain text
• for images, use sans serif font and use anti-aliasing to improve legibility
• use beveling

Imagemaps

• smaller is better (e.g., <50K)
• provide text links beneath imagemap
• links on the imagemap should be obvious
• avoid too much wasted space

Testing

• Preview your webpages
  • in varous browsers, including previous versions
  • at different resolutions
  • at different color depths
  • at different browser widths
  • on different platforms