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Graphic Types and Electronic Presentations
Most of the images that you would use in an electronic
presentation are either Raster images or Vector images.
Raster
Raster images (bitmaps, for example) are made up
of individual pixels. They are determined by their width, height, and depth. Raster images have
fixed dimensions; their file size increases with the size and resolution of the image.
- Color Depth in Raster Images
The number of colors in a raster image determines its color depth. One-bit images have only two states: white and black.
Vector
Vector images are mathematical descriptions of an
image. A computer application "reads" the description of the image and builds that image on the
screen. Consequently, vector images are resolution independent: they can be scaled to any size
and resolution for display on screen, printers, and the like. Because vector images consist of
instructions, rather than pixels, they are usually smaller than comparable Raster images. As
you might expect, these are the best images to use for presentations that will be delivered on
different output devices.
Other Terms
- Color depth
Refers to the number of colors in each pixel.
- GIF (Graphic Interchange Format)
This is the standard graphic format for the web. Chances are, if you want to pull an image
from the Internet and use it in your presentation, it will be a GIF.
- Resolution
Refers to the physical information space of a given output device. For example, a computer
display typically has between 72-120 pixels per inch. The monitor usually is between 15-21 inches, diagonally.
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Basics
Visuals
