GIF vs JPG: PNG? (was Help about Microsoft PowerPoint

[Thomas Keene (LIS)]

> Dan Lester wrote:
> 
> >From what I can see, there is NO reason to not
> >convert all your web images to .jpg, since the last several
> >versions of all the browsers support them.

Jpegs and gifs use different compression techniques.  For a particular
image one or the other of these methods may be preferable.  Photos, for
example, almost always look best as jpegs and are smaller files in that
format than if they were converted to gifs.  On the other hand, simple
geometric shapes with well defined borders between colors (like national
flags) work much better as gifs.  And with gifs you can reduce the color
depth to reduce file size.  Jpegs need the ability to depict 16 million
colors.  If you only need 16 colors in your image, using the gif format
you can reduce your  depth to only 4 bits, which can result in a
significantly smaller file size.  I won't go into the other strengths and
weaknesses of each format.

So basically jpg and gif do different things well and depending on your
image you can choose the best format for the job.  Of course, this only
addresses technical issues and not the intellectual property question
regarding gifs.


  %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
     Tom Keene, Visiting Instructor            
     School of Library and Information Science 
     University of South Florida               
     Internet:  keene at luna.cas.usf.edu         
  %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%


> 
> At least one good reason: TRANSPARENCY.  I have not seen or heard that you
> could make transparent images in JPEG format.  However, the issues that you
> mention over the GIF format are real and it seems that there could be an
> alternative offered by the PNG format: Portable Network Graphics.  I know
> little myself about that format but I did a quick search and found these
> sites:
> 
> http://www.wco.com/~png/
> http://www.boutell.com/boutell/png/
> 
> PNG is not yet supported by Web browsers (apart for some plugins).  We may
> have to stick with GIF for a while.
> 
> LucG
> 
> 
> -------======<<<<<>>>>>======-------
>             Luc Grondin
>      Bibliothecaire/Librarian
>      Bibliotheque des sciences
>   Universite du Quebec a Montreal
> -------======<<<<<>>>>>======-------
> 
>