🚀 go-pugleaf

Andy Mabbett <andy@pigsonthewing.org.uk> wrote:

>well, I was thinking of "black & white" sketches and charts, like those
>at:
>
>        <http://www.westmidlandbirdclub.com/research/bbcbbs/news-3b.htm>
>
>        (NB page still unfinished draft)
>
>
>where the six smaller maps were originally like the largest.
>
>I suppose I could simply "flood" the white in the originals with the
>same background colour as used on the page, but if I ever change that,
>or where users are not seeing the background colour, that would be
>messy.
>
>(I'd be happy to see how folks would make the large map transparent)

Transparent GIFs are an absolute doddle to do if you have the right
software.

GIF files can contain Control Blocks which specify various properties
for the image blocks within the GIF file.  One of these properties is
which colour is to be considered as transparent.  Tools which allow
you to set the transparency will allow you to select which colour is
to be transparent usually by either selecting that colour from the
image's colour palette or by means of a dropper tool.  If irfanview
doesn't include this facility then get yourself GIF Construction Set
from Alchemy Mindworks:
http://www.mindworkshop.com/alchemy/alchemy.html


Then use it to insert a control block into the file before the image
block in which white is marked as the transparent colour.  This will
give you images you need.  If for any reason you can't do this then
e-mail the images to me and I will do it for you and send them back to
you.  Note the spam-trapped e-mail address.

>Incidentally, why does saving a 256-colour GIF as a 5-colour GIF
>sometimes result in a larger file?

Don't know, but some programs write comment blocks and other
superfluous blocks into GIF files which make them larger than
necessary, particularly if they are unregistered shareware.

-- 
Mike Humberston
WARNING: Spam trap in operation. Send any e-mail reply to mike, not oblivion.