CPSC 461: Copyright (C) 2003 Katrin Becker Last Modified May 25, 2003 10:20 PM
FILE FORMATS
Scientific & Graphics Formats
Main Data File Format Types:
Documents (text; word-processor; LaTex; postscript; etc.)
Electronic Data Interchange (EDI : formats for e-commerce)
Scientific
Graphics (raster; vector)
Audio (sound & voice)
Animation (moving pictures)
Multimedia (video; combined)
GRAPHICS: "Pictures"
2 main classes of sources:
1. Computer generated
2. Natural source ("photos")

(computer generated) CG
natural source

cartoon-like
photographic

fewer colours (256?)
Many colours (24-bit)

largish patches of identical colour
very few regions of identical colour

easier to compress
achieving high compression is trickier
uses
cartoons; icons; backgrounds
photographs
2 main kinds of image files:
1. Raster (bitmap) describes pixels - it's actually a PixelMap
2. Vector ("OO") describes lines and shapes

Raster
Vector
typical application programs used to create
paint programs
draw programs
representation
pixel values
line segments
scalability
awkward
easy to scale without loss of information
device dependence
moderate
high
processing speed (for display)
fast
slow(ish) - must be computed
effects such as smoothing; distortion; sharpening; edgeing; etc.
straight-forward
challenging
"tweening" for animation
pains-taking
straight-forward
uses:
scientific data; pictures; www display; animation
mapping; CAD-CAM; architectural drawing; some animation
Examples: (Which is which?) GIF, JPEG, Encapsulated PostScript, BMP, WMF, PNG, PNM

What goes into a raster file? (Stored Image Format)
2-D Array of Values: 1 for each pixel (uncompressed)
- could be: 1 bit (black and white)
- 8 bits: grey-level or 256-colours
- 24 bits (3X 8 bits):
- Intensities of RGB
- Lookup table values for RGB
- 24 bits : lookup table into triples
- Index to some other data structure used to represent a colour
- Several spectral samples for each colour (eg. high frequencies => edges; rapid change in intensity)
There are many ways to organize these sets of values.
(c) 1981-2002 The Computer Language Company Inc.
All rights reserved. Ver. 15.1, 1st Quarter 2002
Computer Desktop Encyclopedia, Alan Freedman

A Monochrome Bitmap
The left half of this diagram shows the bits in the bitmap, and the right half depicts what would show on screen. In monochrome systems, one bit is used to represent one pixel. Images that are scanned into the computer are turned into bitmaps, and bitmaps can be created in a paint program.
What goes into a vector file?
- Specified through primitives: lines; circles; text strings; 2D objects; could be 3D objects; colours (and their attributes)
- Colour information (colour maps)
- since most display devices are in fact raster devices (exception: plotters), these will have to be transformed into pixel values before they can be displayed.
There are also many ways to organize these sets of values.
(c) 1981-2002 The Computer Language Company Inc.
All rights reserved. Ver. 15.1, 1st Quarter 2002
Computer Desktop Encyclopedia, Alan Freedman
Drawing Vs. Painting

Although more painting tools are added to drawing programs and more drawing tools are added to paint programs, their inherent structure is different. Drawing programs (vector graphics) allow for the creation of objects that can be manipulated independently. Paint programs (bitmapped graphics) provide a canvas that can be covered with electronic paint.
SCIENTIFIC:
- often images of a sort, bitmaps
- also need annotations and data organization info
- need detailed info about the data set
- usually some sort of reading of something
- need to know who, what, when, where, why, with what, .....
Examples:
BUFR (Binary Universal Format)
GRIB (Gridded Binary Format) - meteorological data
CDF (Common Data Format) - NASA
DLS - Digital Log Interchange Standard / RP66 (Recommended Practise 66) - well log data
Schlumberger (started American Petrolium Institute)
FITS ( Flexible Image Transport System) - astronomical data
PDS (Planetary Data System) NASA
PLOT 3D - fluid dynamics - NASA
SEG (Society of Exploration Geophysists) - 5 types
- goals & needs are different
- some overlap
Scientific
Graphics
Most Important Aspect
numbers (values rather than appearance)
pictures
Compression
Lossless ONLY (The astronomers wouldn't like it much if we lost stars)
Lossy might be acceptable
Back to TopCPSC 461: Copyright (C) 2003 Katrin Becker Last Modified May 25, 2003 10:20 PM