Scanning and Images

Tom Kelliher, CS 102

Nov. 26, 2001

Administrivia

Announcements

Assignment

Start your home pages.

From Last Time

Outline

1. Overview of using a scanner.

2. Properties of images.

Coming Up

Scanner and Paint Shop Pro labs.

Using the Scanner

Scanner usage notes:

1. Windows 98, the network password, and network drives.

2. Paint Shop Pro.

3. 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?

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

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

5. Logging off --- Log Off don't 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.

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: Right-click, Save as.

12. Copyrights.