1. Class Outline

Administration

Computers and Culture

Digitization = Sampling and Quantization

Digitization of Text


2. Computers and Culture

Stories that circulate electronically

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Urband Legends

Mrs. Fields Cookie legend

What do these tell us about the Internet?


3. Administration

Homework - Due Friday!

Web Topic Paper due in two weeks

Hand it print out of rendered HTML and disk with HTML
We care about writing!

4. Input and Output Model

Computer as input, processing and output

Digitization is input



5. What can be digitized?

Text (Strings of Alphanumeric Characters)

Images (Drawings, Pictures)

Sound (Midi Sequences, Digitized Audio)

Moving Pictures (Video, Animations)

3-D Spaces or Objects (Virtual Reality)

Procedures and Processes

What cannot be digitized?


6. What is digitization?

Analog to Digital

Continuous to Multi-level



7. What is digitization?

Sampling and Quantization



8. Digitizing Text



9. How do we digitize texts?

"Born Digital"

Typing it in
Specialized input tools (Pen Interfaces and Mini-keyboards)

Raw Digitization - OCR

Scanning an image of page
Optical Character Recoginition

This is true of all media!


10. What is an electronic text?

A digital file meant to be read

Sequence of characters that are legible when output

A word processing file

Proprietary formats like MS Word
Open formats like PDF

Open text formats

ASCII (American Standard Code for Information Interchange
Click Here
HTML and XML are built on ASCII

11. ASCII

Digitization and Codes

All information on the computer is coded
Codes depend on a lookup table
Codes have to be transformed

ASCII Codes are 8 bits

8 bits (one byte) means 256 possibilities
ASCII defines 128 of those (lower ASCII)
Extended ASCII not standardized
Extended ASCII defines upper 128

Digital code can only be interpreted if system knows the code

Raw data is useless unless you know what code system
But, you can transcode!

12. What do we lose and gain?

Losses

We lose material presence of paper and print
We lose detail and art of print

Gains

We can duplicate without loss
We can transmit
We can manipulate and transform

13. Digitizing Images

Sampling and Quantizing

Scanner samples millions of points
Assigns a value to each point based on a colour table

Digital Image

Continuous image converted to bit-map of pixels




14. Caligraphic to Graphic Screen

Caligraphic Screen - 80 columns by 60 rows

Monospaced text
No graphics


1984 - Apple Macintosh

Graphic Screen

Bitmap screen where every pixel can be addressed
Screen described as matrix of pixels (Picture Elements)
Even text is now rendered as an image

Digital Cameras

How are they changing the culture of pictures?

15. Scanning Process



16. Bitmap and Vector

Two types of images

Bit-map is digitized (Scanner or Digital Camera)
Vector is typically born-digital (Drawing with Mouse)

Bit-map Image

A matrix of pixels (picture elements) each specifying a particular colour or shade of gray.

Vector

A formal description of the shapes to be generated by the computer.

17. Issues for Images

Image format

What image format to use?

Resolution

How much resolution do you need?

Colour Depth

What colour depth is needed?

Compression

Can compression help?

18. Common Graphics Formats

GIF – Graphics Interchange Format

Uses compression
Two versions 87a and 89a (animated gif, interlacing)

JPEG – Joint Photographic Experts Group

Different levels of compression
Better for photographs, Less efficient
Open standard

Postscript

Vector, resolution independent

19. Resolution

How many pixels per square inch

Higher resolution = more detail
Higher resolution = larger files


Output resolution

Screen = 70 - 90 dpi
Laser Printers = 300 to 600 dpi
Typesetters = 1200-2400 dpi

Higher resolution can be scaled down, lower can’t be scaled up.


20. Colour Depth

1 bit = black and white (2^1 = 2 colours)

8 bit = 256 colours (2^8 = 256 colours)

Useful colour for games and information

24 bit = 16 million colours

Realistic photo quality images for publication
(2^24 = 16,777,216 colours)

Created by Geoffrey Rockwell, October, 2003