BRIGHAM YOUNG UNIVERSITY
BRIGHAM YOUNG UNIVERSITY
Humanities Technology and Research Support Center
Preparation
Graphics common on the computer. [Show some examples.] Before they can appear on the web they must be put into a format that can be displayed on a computer.
Analog = "continuous", "analagous" to nature.
Examples:
Traditional photograph: Light makes "imprint" on photosensitive medium
Vinyl Records: grooves on record cause the stylus head to vibrate and transmit vibrations to amplifier, similar to the way the eardrum works
Magnetic tape: vibration patterns are stored on magnetic tape and reproduced when played back.
Digital = "sampled" collections of brief moments or small parts, stored as 1's and 0's, then interpreted by computer to reproduce the color, sound frequency, etc.
This process takes advantage of the practical limitations of the human senses: In the real world there is far more data than we need to interpret what we're seeing or hearing. So an apparently continuous image is really a dense collection of colored pixels. [Open an image in GraphicConverter and blow up to high magnification and look at the pixels.]
For digital images, there are usually between 72 and 96 dots per inch (DPI) for an image on a computer screen. (Mac is 72 or 75 dpi; Windows is 96 dpi.)
Print media require much denser resolution to produce a smooth-looking image (300 to 1200 dpi).
Originally, computer monitors had only two possible colors: black and something else (green, amber or white, usually.) The screen could be thought of as a flat surface made up of individual dots of light, picture elements, or "pixels". In the old, one-bit systems each pixel could be either off (0) or on (1). You could store an image as a map of bits, or "bitmap".
A black and white bitmap in memory and on screen.
As technology progressed, color monitors made it possible for each pixel to display more than just two states. Instead of just black and white, now each pixel could display black, white, and a range of other colors. One of the most common examples of a bitmapped graphic is a scanned or digital photograph.
A Scanned Photo (JPEG format)
Mount Shuksan, Washington
1. Resolution (dpi) or density. Typical resolutions: 72, 75, 96, 300, 600, 1200. When considering digital cameras, one of the factors is its megapixel rating. This refers to the resolution of the images created. Low end cameras - 1 to 3 megapixels; mid-range - 4 to 6 megapixels; professional, high end - 7 megapixels or higher.
2. Bit Depth. This refers to the number of different colors that can be displayed for any given pixel in the image:
Back CHum Revolution Gateway
Bits Number of Colors Example 1 2 (black & white) 1-bit image 2 4 2-bit image 4 16 4-bit image 8 256 8-bit image 16 32,768 16-bit image 32 16,700,000