[Coco] GIF

[Roger Taylor]

At 11:52 PM 12/20/2003 -0500, you wrote:
>In a message dated 12/20/03 10:46:17 PM Eastern Standard Time,
>johnguin at hotmail.com writes:
>
> > I thought another reason GIF lost popularity to JPG was JPGs were "lossy"
> >  and could be compressed, but GIF was locked into "only" 256 colors and no
> >  compression.

JPG has superior compression abilities with a tradeoff of losing 
quality.  This "dial-a-quality" is handled by the encoder.  Some pictures 
compress very well and look the same... some don't.  The term "lossy" comes 
from the fact that you lose quality as the compression ratio 
increases.  JPG also takes into consideration the way the human eye works, 
sometimes giving priority to color OR luminance, but not necessarily both.

GIF does not alter or reduce colors, so it is not a lossy format.  What you 
compress is what you get when you decode.


>Well, those are certainly valid limitations of GIF.  I stopped using GIF for
>anything (other than line drawing schematics) after I upgraded to a PC with
>more than 256 colors.  Once I went to 24-bit truecolor, or even 16-bit
>highcolor, my previous GIF photos looked really grainy due to every pixel 
>being forced
>into one of 256 colors.

Actually, a 256-color dithered GIF can have stunning quality, especially a 
640-wide image or greater.  Even without dithering, I've seen too many HQ 
GIFs to say bad things about the format.


----------
Roger Taylor


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