Understanding Graphics for Creating Computer-Based Multimedia Projects & Web

Pages

Adapted by Helen Mongan-Rallis from

presentation by Andrea Pokrzywinski

(used with permission for

Educ 5415)

Monitor Colors RGB

1 Bit Black and White

24 Bit Color

216 Web Safe Colors

•Macintosh Computers and Window computers have different color indexes of 256 colors

•Web safe: only 216 colors that match perfectly on the monitor when seen on both platforms

• Thus, for reliable graphic design, use only web safe colors

Graphic Compression

•Graphics files take up a lot of memory

•Causes sluggish performance on web sites with graphics

•Two types of graphic compression formats have been become standard for web use.

JPEGGIF

JPEG

Joint Photographic Experts Group-A compression standard developed for still images.

JPEG compression is recommended for photographic -style images and continuous -tone images (e.g. used for backgrounds).

JPEG Compression is Variable

42K32K

36K

JPEG images pixelate as they are enlarged

GIF

Graphics Interchange Format A graphic compression format

developed by CompuServe to allow graphics to load quickly on easily through a network.

Best used with flat graphics and such as logos and drawings.

GIF - Indexed Color Limited to 256 Colors

GIF vs. JPEG

JPEG=15,343 bytes GIF=26,979

http://www.rit.edu/~bdb7236/mmwww/picthis.html

Gif vs JPEG

JPEG=42,268 bytes GIF=21,507 byteshttp://www.rit.edu/~bdb7236/mmwww/picthis.html

Transparent GIF’s Gif files will allow you to set one color to

be transparent. This means it will allow the web pages background to be viewed through this color.

TransparentNot Transparent

Placing transparent objects on background colors that match the transparency color will prevent haloing seen in the previous slide.

Interlacing

Interlacing allows the picture to gradually fill in by adding lines top to bottom and repeats this till the image is complete.

Standard format fills from top to bottom.

Interlacing allows the viewer to see a preview of the entire image before it finishes downloading .

The image on the UMD Psychology dept. web site at http://www.d.umn.edu/psychology/people/index.html is interlaced. Notice how it loads…

Anti Aliasing Anti-Aliasing smoothes the edges of a

graphic.

DPI - Screen Resolution

•Monitors read 72 dots per inch in resolution

• Thus there are about 5,200 dots per square inch.

•Printed documents usually use 150 dpi or higher with 1, 440, 000 dots per square inch.

•For web photos, set your image resolution to 72 dpi.

•Sony Mavicas are set to take 72 dpi photos

Pixels•72 pixels to an inch.

•Pixels are the standard measuring tool for computer monitors.

•Web page designers design with for a monitor view of 640 pixels wide and 480 pixels in height as a standard.

•This allows for the lowest common denominator in monitors to view the entire screen. This will change with advances in technology.

Hexadecimal Color CodesWeb colors are coded in six digit code combining numbers and letters. You can find the codes for web safe colors on web sites for graphics editors or it will be built into sophisticated web graphic editing programs like fireworks.

#33CC00

Creating Graphics Draw a graphic from

scratch Scan a picture with a

scanner Draw using graphic

applications (e.g. PhotoShop, AppleWorks Draw, or PowerPoint draw tools)

Capturing Graphics Copying from the Web

Free Web Art Site

http://www.mccannas.com/

Purchasing Image CD’s

Eyewire product index http://www.eyewire.com/index/

Further Information

Creating World Wide Web Graphicshttp://www.envisiondev.com/idug/

oct96_w/wg_main.htm Making Web Graphicshttp://www.geocities.com/SiliconValley/

Heights/1288/making.html Creating Graphics for the Webhttp://www.widearea.co.uk/designer/