How Computer Graphics Work

Pixels Everywhere
Computer graphics are literally everywhere you look. Product packaging, advertising, trading cards, books, technical drawings, logos, checks, credit cards and signs just to name a few. The list just goes on and on.

A computer graphic is an image that has been converted from an input device such as a scanner or digital camera to a computer file so that it can be interpreted by a graphics program. A graphics program is software designed to convert the file to an image which can be displayed on a monitor allowing manipulation, editing or print-out of the image.

What's A Raster?
Most graphic formats use the bit mapped (AKA raster) method to store files. An image is stored as rows of pixels starting from the top left pixel to the bottom right pixel. Information for each pixel is stored in this string of binary code which is recorded to a disk. The more pixels, the larger the file size Depending on resolution and image dimensions, file sizes can become quite large.

How Else Could You Store A File?
Vector graphics formats also known as Computer art can add even more control and versatility to the digital artist. Unlike "raster" (AKA bitmap/paint) formats, vector files store shapes, colors and layers as mathematical formulas. High quality image can be rendered taking up very little disk space because the information for each pixel does not have to be stored. Since vector images are composed of mathematical formulas, the resulting image can be enlarged without loosing any quality of appearance.

A vector image can be converted to a .gif or compressed .jpg format for use on a Web site or virtually any other format. Other graphic elements such as graphs and charts and tables are relatively easy to create. We will not be covering "vector" images in this class but I encourage you to try it out to see what the differences are. Some examples of vector image software are Adobe Illustrator (formerly Aldus), Macromedia Freehand and Corel Draw.

Image Properties describe different aspects of an image such as size, color depth, resolution and other information related to the format of the file. The square below is 1 inch x 1 inch, the color depth is 1bit (two color), and the resolution is 72 pixels per inch also called dpi (dots per inch).

The squares below also have a color depth of 1bit (two color), and is 72 dpi (pixels). I have alternated the color of every other pixel between black and white in the stripe through the square on the left. The square to the right is what you would see if you zoomed in on the square with the stripe.

Color Depth
1bit=2 colors
4bit=16 colors
8bit=256 colors
16bit=65,536 colors
24bit=16.7million colors
32bit=4.29billion colors
64bit=what comes after trillion?