Page 153 - DCAP104_EXPOSURE_TO_COMPUTER_DISCPLINES

Exposure to Computer Disciplines

Notes 7.3.4 Metafile Formats
Metafiles can contain both bitmap and vector data in a single file. The simplest metafiles resemble
vector format files; they provide a language or grammar that may be used to define vector data
elements, but they may also store a bitmap representation of an image. Metafiles are frequently
used to transport bitmap or vector data between hardware platforms, or to move image data
between software platforms.
WPG, Macintosh PICT, and CGM are examples of commonly used metafile formats.
7.3.5 Scene Formats

Scene format files (sometimes called scene description files) are designed to store a condensed
representation of an image or scene, which is used by a program to reconstruct the actual
image. What’s the difference between a vector format file and a scene format file? Just that
vector files contain descriptions of portions of the image, and scene files contain instructions
that the rendering program uses to construct the image. In practice it’s sometimes hard
to decide whether a particular format is scene or vector; it’s more a matter of degree than
anything absolute.

7.3.6 Animation Formats
Animation formats have been around for some time. The basic idea is that of the flip-books you
played with as a kid; with those books, you rapidly displayed one image superimposed over
another to make it appear as if the objects in the image are moving. Very primitive animation
formats store entire images that are displayed in sequence, usually in a loop. Slightly more
advanced formats store only a single image but multiple color maps for the image. By loading
in a new color map, the colors in the image change, and the objects appear to move. Advanced
animation formats store only the differences between two adjacent images (called frames) and
update only the pixels that have actually changed as each frame is displayed. A display rate of
10-15 frames per second is typical for cartoon-like animations. Video animations usually require
a display rate of 20 frames per second or better to produce a smoother motion.

TDDD and TTDDD are examples of animation formats.
7.3.7 Multimedia Formats

Multimedia formats are relatively new but are becoming more and more important. They are
designed to allow the storage of data of different types in the same file. Multimedia formats
usually allow the inclusion of graphics, audio, and video information. Microsoft’s RIFF, Apple’s
QuickTime, MPEG, and Autodesk’s FLI are well-known examples, and others are likely to emerge
in the near future.
7.3.8 Hybrid Formats

Currently, there is a good deal of research being conducted on the integration of unstructured text
and bitmap data (“hybrid text”) and the integration of record-based information and bitmap data
(“hybrid database”). As this work bears fruit, we expect that hybrid formats capable of efficiently
storing graphics data will emerge and will steadily become more important.
7.3.9 Hypertext and Hypermedia Formats
Hypertext is a strategy for allowing nonlinear access to information. In contrast, most books are
linear, having a beginning, an end, and a definite pattern of progression through the text. Hypertext,
however, enables documents to be constructed with one or more beginnings, with one, none, or
multiple ends, and with many hypertext links that allow users to jump to any available place in
the document they wish to go.

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