Re: Support for Vector Images

Clive Bruton (clive@typonaut.demon.co.uk)
Mon, 1 Dec 97 13:52:49 +0000


Date: Mon, 1 Dec 97 13:52:49 +0000
From: Clive Bruton <clive@typonaut.demon.co.uk>
To: <www-html@w3.org>, <www-style@w3.org>
Message-ID: <1331137982-46955487@[194.205.134.101]>
Subject: Re: Support for Vector Images

David Perrell wrote at 30/11/97 10:58 pm

>Chris Lilley asked:
>>
>>Did this saving carry over to other files, or did you just test a single
>>instance?
>
>I did the test with remembrances of times when I did more print work. I'd
>use CGMs for layout, then replace with EPS (w/o embedded positioning
>bitmaps) for imaging negs. The CGMs were always smaller. I found two more
>examples:
>
>  complicated border -- CGM:  37k  EPS: 257k
>  another logo --       CGM:  14k  EPS:  59k


I think such comparisons need a little objectivity, to baldly state that 
CGM is more compact than EPS may ignore many factors:

     Are we really comparing like with like, does the CGM file
     contain the same information (in terms of colour and vector
     coordinates).

     Any EPS will usually contain a pre-rasterised header, which
     will consume disk space but may be irrelevent when transporting
     a file that will be rasterised on-the-fly to screen.

     EPSs generated by popular vector drawing apps (Freehand and 
     Illustrator for example) may contain additional information
     pertaining to their structure including:

          Colour palettes
          Layer information
          Small speadsheet type info for charting
          Grouping info
          Several colourspace definitions

As a further comparison I'd consider PDF to be everything an EPS is (and 
more) without some of the above noted overheads, so grabbing some info 
that I just happen to have to hand:

     EPS  182k      Contains several complicated shapes, colour 
                    and layer info, as well as a header.

     PDF  28k       Essentially the raw shapes


Thus I'd suggest that PDF and CGM are better comparisons, than EPS and 
CGM.


-- Clive