File Formats and Compression


File Formats

File formats determine the kind of information to be saved in a file, the compatibility with various software applications and the exchanging of data in the production  . There are some  factors affecting the saving of a scanned image. Which program you'll use to post-process the image? How much disk storage is available? Will you exchange the file with others during production or the eventual output media?

Please refer to the following table.

File Format File Extension Recommended
Output Media
Advantages
TIFF .tif Print
  • Efficient file size 
  • Save color separations in a single channel
EPS .eps, .epsf Print
  • Save duotone information 
  • Save clipping path 
  • Save color separations in 1 or 5 channels.
PCX .pcx Multimedia, Presentation, Video Used by most software application.
PICT .pict, pct Multimedia, Presentation, Video
  • Compact file size 
  • Include both raster and vector information
BMP .bmp Multimedia, Presentation, Video
  • Used by most software application
Targa .tga Multimedia, Presentation, Video
  • Save alpha channel information
JPEG .jpg Multimedia, Presentation, Video
  • With the best compression ratio (40:1)

Compression

File compression schemes fall into two general categories:lossy and lossless. Lossless compression schemes pack the data in a file without actually deleting information, therefore, there is no loss to image details, color or output quality. The lossless compression options include the disk and file compression utilities (for example, DiskDoubler, PKZIP, ARJ or LHARC) and the type of TIFF format with LZW (Lempel-Ziv-Welch) compression.

If the 2:1 compression ratios are not high enough, lossy compression has to be considered,.The most popular lossy compression option is JPEG standing for the joint Photographic Experts Group, which developed the compression standard JPEG.Compression ratios can be selected  from 2:1 to about 40:1 by your requirements..