R

radial gradient

A gradient that is projected from a center point outward in all directions.

random access memory (RAM)

The part of the computer s memory that stores information temporarily while the computer is on.

raster image

An image that consists of a grid of pixels. Raster images are also called bitmaps. The file sizes of raster images are usually quite large compared to other types of computer-generated documents, because information needs to be stored for every pixel in the entire document. See also raster-based software .

raster image processor (RIP)

Software on a computer or a device inside an imagesetter or PostScript printer that interprets a vector curve by connecting a series of straight-line segments.

raster-based software

Photoshop and other programs that create raster images. Raster-based software is best suited for editing, manipulating, and compositing scanned images, images from digital cameras and Photo CDs, continuous-tone photographs, realistic illustrations, and other graphics that require subtle blends, soft edges, shadow effects, and artistic filter effects such as Impressionist or watercolor.

rasterize

To convert vector information into pixel-based information. For example, you can rasterize type so that you can apply filters and other effects that do not work on vector-based type. Rasterized type cannot be edited as individual characters and appears at the same resolution as the document.

red eye

An effect from flash photography that appears to make a person s eyes glow red.

registration mark

A mark that appears on a printed image, generally for color separations, to help in aligning the printing plates.

rendering intents

Settings established by the International Color Consortium (ICC) under which color conversions can be made. Rendering intents cause the color of an image to be modified while it is being moved into a new color space. The four rendering intents are Perceptual, Saturation, Relative Colorimetric, and Absolute Colorimetric.

resample

To change the size or resolution of an image. Resampling down discards pixel information in an image; resampling up adds pixel information through interpolation.

resolution

The number of units that occupy a linear inch of an image ” measured in pixels per inch (ppi) on an image or monitor, or dots per inch (dpi) on a printer. The resolution of an image determines how large it will appear and how the pixels are distributed over its length and width. Resolution also determines the amount of detail that an image contains. High resolutions produce better quality but larger image file sizes. Resolution can also refer to the number of bits per pixel.

resolution-independent image

An image that automatically conforms to the highest resolution of the output device on which it is printed.

RGB color mode

A color mode that represents the three colors ”red, green, and blue ”used by devices such as scanners or monitors to display color. Each range of color is separated into three separate entities called color channels. Each color channel can produce 256 different values, for a total of 16,777,216 possible colors in the entire RGB gamut . RGB is referred to as an additive color model. Each pixel contains three brightness values for red, green, and blue that range from 0 (black) to 255 (white). When all three values are at the maximum, the effect is complete white.

RGB image

A three-channel image that contains a red, a green, and a blue channel.

rollover

A mini animation that is activated by mouse behavior. Rollovers add interactivity to a Web page. Rollovers depend on layers for their behavior. You designate a rollover on an image by changing the visibility of a layer s content.