| Graphical images can be line art (b/w), grayscale, or color. |
- Number of bits...
- Line art (bitmapped) images
- Gray scale images
- Color images
| Resolution |
- Measured in dots per inch
- Image resolution effects image quality
- high resolution for printing
- screen resolution for Web
- dpi = "dots" per inch
- ppi = "pixels" per inch
- dots = pixels
resizing images up
and down
| Graphic file types
TIFF, PCX, PICT, EPS, BMP, GIF, JPEG, PNG, PSD, TARGA, many others |
- Compuserve GIF
- Graphics Interchange Format
- 1 bit to 8 bit
- developed by Compuserve
- can only be 256 colors
- built-in LZW compression (lossless)
- progressive display ("interlaced")
- GIF89
- same as Compuserve GIF
- has transparency
- JPEG
- Joint Photographers' Expert Group
- 1 bit to 32 bit
- built in JPEG compression option (lossy!)
- compression only works with 16 to 32 bit
- TIFF
- Tagged Information File Format
- 1 bit to 32 bit
- built in LZW compression option (lossless)
- compression works with all types
- hardly supported on the web
- the format for scanning and faxing
- PNG
- Portable Network Graphics file
- 1 bit to 32 bit
- lossless compression
- carries metadata (e.g. author's name)
- transparency
- progressive display
- still limited browser support
| Benefits of using compression |
- Less hard disk space used for storage
- Less time for Internet transfer
- modem users !!!