Class Outline


Computers and Culture

Digitization = Sampling and Quantization

Digitization of Text


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?



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!


Input and Output Model

Computer as input, processing and output

Digitization is input


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?


What is digitization?

Analog to Digital

Continuous to Multi-level


What is digitization?

Sampling and Quantization


Digitizing Text


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!


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

HTML and XML are built on 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!


What do we lose and gain?


We lose material presence of paper and print

We lose detail and art of print


We can duplicate without loss

We can transmit

We can manipulate and transform


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


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?


Scanning Process


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.


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


Issues for Images

Image format

What image format to use?


How much resolution do you need?

Colour Depth

What colour depth is needed?


Can compression help?


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


Vector, resolution independent



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.


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