<HTML> <HEAD> <META HTTP-EQUIV="Content-Type" CONTENT="text/html; charset=iso-8859-1"> <META NAME="GENERATOR" CONTENT="Mozilla/4.01 [en] (Win95; I) [Netscape]"> <TITLE>2. Scanning Concepts</TITLE> </HEAD> <BODY TEXT="#000000" BGCOLOR="#FFFFFF" BACKGROUND="../icon/body.jpg"> <CENTER><B><FONT FACE="arial"><FONT COLOR="#FF7D00"><FONT SIZE=+2>Chapter 2. Scanning Concepts</FONT></FONT></FONT></B></CENTER> <P><B><FONT FACE="arial">2.4 File Formats and Compression</FONT></B> <BR><B><FONT SIZE=+1>Depending</FONT></B> on the contents of your documents, basically, we can classify them into three image types. <P><A NAME="a"></A><FONT COLOR="#FF7F00">2.4.1 File Formats</FONT> <BR><B><FONT SIZE=+1>Determine</FONT></B> the kind of information to be saved in a file, the compatibility with various software applications and the exchanging of data in the production process. There are some influential factors in saving a scanned image. What program you'll use to post-process the image? How much disk storage is available? Will you exchange the file with others during production process and the eventual output mediums? <P><B><FONT SIZE=+1>Please</FONT></B> refer to the following table. <TABLE BORDER > <TR> <TH>File Format</TH> <TH>File Extension</TH> <TH>Recommended <BR>Output Media</TH> <TH>Advantages</TH> </TR> <TR> <TD VALIGN=TOP><A HREF="../HTML/7.htm#t1">TIFF</A></TD> <TD VALIGN=TOP>.tif</TD> <TD VALIGN=TOP>Print</TD> <TD> <LI> Efficient file size </LI> <LI> Can save color separations in a single channel</LI> </TD> </TR> <TR> <TD VALIGN=TOP><A HREF="../HTML/7.htm#e">EPS</A></TD> <TD VALIGN=TOP>.eps, .epsf</TD> <TD VALIGN=TOP>Print</TD> <TD> <LI> Can save duotone information </LI> <LI> Can save clipping path </LI> <LI> Can save color separations in 1 or 5 files.</LI> </TD> </TR> <TR> <TD VALIGN=TOP>PCX</TD> <TD VALIGN=TOP>.pcx</TD> <TD>Multimedia, Presentation, Video</TD> <TD VALIGN=TOP>Used by most software application.</TD> </TR> <TR> <TD VALIGN=TOP><A HREF="../HTML/7.htm#p">PICT</A></TD> <TD VALIGN=TOP>.pict, pct</TD> <TD>Multimedia, Presentation, Video</TD> <TD> <LI> Compact file size </LI> <LI> Can include both raster and vector information</LI> </TD> </TR> <TR> <TD VALIGN=TOP><A HREF="../HTML/7.htm#b1">BMP</A></TD> <TD VALIGN=TOP>.bmp</TD> <TD>Multimedia, Presentation, Video</TD> <TD> <LI> Used by most software application</LI> </TD> </TR> <TR> <TD VALIGN=TOP><A HREF="../HTML/7.htm#t">Targa</A></TD> <TD VALIGN=TOP>.tga</TD> <TD>Multimedia, Presentation, Video</TD> <TD> <LI> Can save alpha channel information</LI> </TD> </TR> <TR> <TD VALIGN=TOP>JPEG</TD> <TD VALIGN=TOP>.jpg</TD> <TD>Multimedia, Presentation, Video</TD> <TD> <LI> With the best compression ratio (40:1)</LI> </TD> </TR> </TABLE> <A NAME="b"></A><FONT COLOR="#FF7F00">2.4.2 Compression</FONT> <BR><B><FONT SIZE=+1>File</FONT></B> <A HREF="../HTML/7.htm#c1">compression</A> schemes fall into two general categories: <A HREF="../HTML/7.htm#l1">lossy</A> and <A HREF="../HTML/7.htm#l2">lossless</A>. Lossless compression schemes pack the data in a file without actually deleting information, so there is no loss to image detail, color or output quality. The lossless compression options include the disk and file compression utilities (for example, DiskDoubler, PKZIP, ARJ or LHARC) and another type of TIFF format with <A HREF="../HTML/7.htm#l3">LZW (Lempel-Ziv-Welch</A>) compression. <P><B><FONT SIZE=+1>If</FONT></B> the 2:1 compression ratios are not high enough, lossy compression has to be considered, the most popular lossy compression option is JPEG, JPEG stands for the Joint Photographic Experts Group, which developed the compression standard JPEG compression ratios are user selectable in the host software and range from 2:1 to about 40:1. </BODY> </HTML>