Graphic File Formats

 

Two major categories: bitmap (also called raster) and vector Bitmapped graphics are grids (rows and columns) Expanding them can cause jagged lines; making them smaller can reduce legibility Icons, Windows wallpaper digital photos, scanned images often saved as BMP Each dot in black and white BMP stored in 1 data bit Color or continuous tone (greyscale) needs additional bits to store information All graphics programs support BMPs =DIB (device-independent bit map)

 

 

4 Most Common Types for Website creation:

 

JPEG/JPG=Joint Photographic Experts Group

uses lossy compression to reduce files to as little as 5% normal size

works best on smooth-edged graphics (continuous tone)

stores full color information (24 bits/pixel=16 million colors)

blurs sharp edges (pure black against pure white)

use to archive photographs

use to publish photographs or greyscale graphics to Web

use for high-end monitor viewing of colors

 

 



 

GIF =Graphics Interchange Format

lossless compressed format (simpler format, downloads quickly)

requires less space than BMP

supported by most graphics programs

stores color information at 8 bits/pixel (256 or fewer colors)

use for images like simple cartoons, black and white line art

 

 

 

TIFF=Tagged Image File Format

uncompressed, supports any size, resolution, and color depth

highest quality, but requires most space and download time

use for state-of-the-art communications, where size is no object

 

 

PNG=Portable Network Graphics

similar to GIFs, gets around patent data compression formula

supported by NN and IE, but never became popular

use in the event of (hitherto unseen) legal complications

 

 

 

 

Useful site:  http://info.med.yale.edu/caim/manual/