Scanning and Images

Tom Kelliher, CS 102

Mar. 24, 1999




Finish up the FrontPage exercises you haven't finished in lab on your own.

Practice the skills you're unsure of on your own.

Make an appointment to see me if you're still lost.

From Last Time

Publishing web pages (better remove your pages on phoenix.)


  1. Overview of using a scanner.

  2. Properties of images.

Coming Up

Scanner lab and Paint Shop Pro.

Using the Scanner

Scanner usage notes:

  1. Before booting the scanner PC, turn on the scanner.

  2. Windows 95, the network password, and network drives.

  3. Paint Shop Pro.

  4. Image size, dpi, pixels, and screen resolution

    Consider a 3 x 5 image scanned at 100 dpi. What is its size in pixels?

    Common screen resolutions: 640 x 480, 800 x 600. Does a browser have all that ``real estate'' available?

    The scanner tool has rules to assist you. Choose dpi carefully.

    You can use Paint Shop Pro to decrease the size of an image.

  5. JPEG (compression) and GIF (transparency and interlacing) formats.

  6. Logging off --- don't accept the default (shutdown).

Some scanned examples:

  1. A photograph:
    1. Size: 2.00 x 2.73 in.

    2. Different DPIs and effect on size.

    3. Different compression factors and effect on size and quality.

    4. GIF vs. JPEG --- size.

  2. Line art:
    1. Different compression factors.

    2. GIF vs. JPEG --- size, quality.

  3. A card:
    1. Removing the screen effect.

    2. GIF vs. JPEG --- size, quality.

    3. Different compression factors. Degradation occurs more quickly.

Things to observe:

  1. Quality.

  2. The sizes of the files. Why do we care?

    The connection between image size, image format, and file size.

Image Properties

  1. Pixels.

  2. Common resolutions:
    1. 640 x 480.

    2. 800 x 600.

    3. 1024 x 768.

  3. Image size.

  4. How much is visible to a viewer, without scrolling?

  5. Formats:
    1. GIF --- interlaced, non-interlaced. Limited to color depth of 256. Transparency. Lossless compression.

    2. JPEG --- Joint Photographs Expert Group. Higher color depths. Compression factors. Lossy compression.

  6. Color depth. Common values:
    1. 2 --- black and white.

    2. 16 --- simple artwork.

    3. 256 --- more complex artwork, photographs.

    4. 32K and higher --- photographs.

  7. Which image format to use? Scanned items: JPEG. Items created in Paint Shop Pro: most likely interlaced GIF.

  8. Size of the image file. Time to load.

  9. In-line and external images.

  10. Thumbnail images.

  11. Acquiring images from web pages:
    1. Drag and drop.

    2. Right-click, Save as.

  12. Copyrights.

Thomas P. Kelliher
Wed Mar 24 08:40:57 EST 1999
Tom Kelliher