Re: Need help with graphics

GIF compresses by using a limted colour palette (256 colours max), and by
effectively saying ditto for groups of pixels all the same colour. So, a gif
with gentle graduations of colour will be a large file, and may represent
colours badly. (But if you have a map with four colours, and use a 4 colour
pallette, compression is impressive)

But, gif accurately represents shapes, and does not distort edges. JPG, on
the other hand, does something like a spatial fourrier transform on little
squares of the image, and represents the shapes as frequencies. Soft
graduations are represented accurately with a small file, sharp edges
generate artefacts if significant compression is used, and the file can
still be disappointingly large.

Therefore, a slight gaussian blur in areas that don't need to show all the
detail halps jpg compression, and making areas of pixels almost the same
into areas *exactly* the same helps gif compression. Usually gif distorts
text less, jpg distorts faces less.

I sometime use a copy of XAT JPEG Optimiser that I got on the cover disc of
a magazine - and it can do a useful job.

Andrew

----- Original Message -----
From: "Klaas De Waele" <klaas(at)gracegraphics.be>
To: "'Doris Harrison'" <dot(at)whc.net>; <hwg-techniques-digest(at)mail.hwg.org>
Sent: Thursday, August 02, 2001 8:11 AM
Subject: RE: Need help with graphics


> Main idea here is to get a program that can compress to gif or jpg.
> Paintshop Pro can do the Job, though I've always been a PhotoShop
> passionate.
>
> Just remember... whichever site you have, first impression of the graphics
> is more important than the actual absolute quality.  By which I mean...
make
> a compromise between size and quality.  Try out gif, which keeps a high
> quality throughout instead of jpeg, which looks muddy when
overcompressing.
> Though jpeg is very nice for colour-rich big photographs.  It's a matter
of
> experience and a good eye.  Which in its turn means you'll have to
> experiment using the amount of colours in the gif, the quality of the
jpeg,
> whether to make it progressive or not,...
>
> Good luck.
>
>
> - Kayjey -
>
>
> -----Oorspronkelijk bericht-----
> Van: owner-hwg-techniques(at)hwg.org
> [mailto:owner-hwg-techniques(at)hwg.org]Namens Doris Harrison
> Verzonden: donderdag 2 augustus 2001 1:54
> Aan: hwg-techniques-digest(at)mail.hwg.org
> Onderwerp: Need help with graphics
>
>
>
> Would someone help me out with my graphics?  Many of them are too large
> and I have resized them but they are still too large and load slowly. Do
> you know of any free programs that can help me with this?
>
> Dorris
>
>

HWG hwg-techniques mailing list archives, maintained by Webmasters @ IWA