FW: [WEB4LIB] Transparent images?

[Gimon, Charles A]

The background that you choose as your "transparent" color should be the
same or close to the background that you will lay the final image over. When
you soften the edges of the objects that are laying over the "transparent"
background color, you want them to blend into whatever color they will
finally be resting on. (For "soften" read "feather", "antialias", or
whatever, depending on your software.)

For example, if you have a red logo that will end up on a grey background,
make your image with that grey or a grey close to it as the background in
that image. That way the red logo edges will blend into grey, creating the
soft edge. You choose the surrounding grey to be transparent. From red to
the edge will go like this:

red > greyer red > greyer red > really grey red > transparent

which will blend in nicely.

The mistake some people make is to choose a color that doesn't match the
final background, say black, as the background color for the transparent
image, since "it'll be transparent anyway". This makes the edges of the red
behave like this:

red > darker red > darker red > blackish red > transparent

so what you end up with is a red logo with a blackish halo effect over your
grey background showing through the transparency. (Or, an image that would
look okay over a mostly black background pattern.)

Note that currently GIF is the only widely supported image format that lets
you define a transparent color, so things that don't look so great in GIFs
(like a fall landscape) won't look good, will be difficult to work with in
this manner, or will end up with a somewhat bloated file size. (Yes, someday
we'll all use PNGs and not worry about it.)

--Charles Gimon
  Web Coordinator
  Minneapolis Public Library

-----Original Message-----
From: Nancy Sosna Bohm [mailto:plum at ulink.net] 
Sent: Monday, July 17, 2000 3:39 PM
To: Multiple recipients of list
Subject: [WEB4LIB] Transparent images?



Here's a chance for those of you graphics experts to show off to your
peers. I am using Photoshop and Fireworks. Is there any way to save a truly
transparent image with soft edges? Everything I read and try involves
faking it by using the background color.
Any response would be appreciated.



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