Glossary of Terms and Concepts

Alpha Channel

A fourth 8bit channel of an RGB file. The greyscale information on this layer acts like a mask for the RGB image where pure black masks out the other channels to create transparancy and pure white has no effect on the image.

Bitmapped Image:

Often called a raster image. A bitmap image is represented by pixels and stored as a collection of bits in which one or more bits of color information corresponds to each pixel. A bitmapped file usually has a .jpg .gif .tif .psd .pict or .bmp extension. This type of image file is generally used for photographic quality (depending on the Bit Depth).

Composite

This refers to the assembling of a final raster image by layering at least two elements together. Composites may have hundereds of layers

Drum Scanner

This is a high-resolution scanner that uses a spinning cylinder to capture nearly 10,000 dpi.

Histogram

A visual map of an images luminance values. A histogram gives you a good representation of how an images tonal values are distributed

Vector Image:

This is an image compiled of mathmatically defined areas that are filled or outlined with color. Vector images can be scaled up or down with out any loss of quality and the size of the file is dramatically smaller then a raster image. A vector image is generally used for graphics.

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