Re: Re: Re: Memory Map query

You really shouldn't save maps as jpegs, save them as gifs instead
(or another 8-bit compressed format).

Do you want the explanation why?

Gordon Burns wrote:

Go on....

Okay then...

Jpeg is a 24 bit format, ideal for photographs, which can have literally
millions of different colours. It uses a lossy compression to keep the file
sizes small, so it smooths out areas of similar colours. At high
compression this gives rise to nasty looking artefacts, but at low
compression (high quality) it works well.

Gif is an 8 bit format, which only supports 256 colours. This makes it a
very bad choice for photographs. If you really must use gif for photographs
(for example if you want to use the transparency feature), there is a
dithering option which improves things, but you really should avoid gifs for
photos. For any image with 256 colours or less though, gif is ideal.

Maps don't have many colours, which is one reason why gif is best. The
other is compression. Gif uses compression, but it's not lossy like jpegs,
so you don't lose any detail. Jpeg compression has a horrible effect on
maps, just zoom into one, it looks awful.

If you know how, you can set the reduce the bit depth of gifs, making the
file sizes even smaller. You can reduce a map to 6 or even 5 bits without
noticing any difference.

Paul


.

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