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Re: Web graphics



At 08:19 08/04/98 -0500, Pamela Rups wrote:
>On the subject of Web graphics.....
>
>Graphics should be as small in *file size* as possible, definitely under 50K.
> The gif file type is preferable since when making them you can often flatten
>them from 8 bit color to 6 bit or less with little or no noticeable image
>degradation (in Adobe Phototshop, for instance).

In case some of you don't know what Pam means by "8 bit color", that refers
to the colour depth (and can you tell she's American and I'm Canadian?<g>).

8 bit colour has 256 colours in it (and they can be any 256 colours, even
just 256 shades of gray). Further...

        8 bit   256 colours
        7 bit   128 colours
        6 bit    64 colours
        5 bit    32 colours
        4 bit    16 colours
        3 bit     4 colours
        2 bit     2 colours

And yes, I must confess, I've made a few two-bit graphics myself in my day. ;)

Of course, you can use any increment of colour depth for your graphic,
whatever might be appropriate (165 colours, 80 colours, 23 colours, etc.)
and any reduction you can get will help reduce the file size -- it's just a
matter of how much quality you're willing to sacrifice.

GIF files, however, can't go any higher than 256 colours, so if you've got
a photograph or something similar (like a picture of a painting, etc.) that
has "16 million" colours, then JPEG format is better. In the JPEG format,
using the right compression level is the key, playing around with the file
and seeing how much compression you can get away with before the quality of
the image is sacrificed. Just remember, though, to save an original copy of
your work at the maximum quality, because once a JPEG is compressed and the
quality is gone, you can't get it back!

With that said, though, in reference to the following...

>Thumbnails on a page are
>great for giving people an idea of an image. A good technique is to have
>small (in physical size and file size) thumbnails of artwork, photos,
>bindings, etc., as gifs on one Web page and have them as links to larger,
>more detailed jpeg images.

...even thumbnails of photographs (etc.) are often better done as GIFs. Try
both, and see which file is smaller. And in other words, yes, it'd be quite
normal to have a GIF thumbnail pointing to a larger version JPEG. (I think
that's basically what you said, Pam, but just confirming.) :)

>You can tell such gifs because they have a
>colored border around them and your cursor changes when you move it over the
>graphic.

Unless the person used <BORDER="0"> in their code, of course.

>When the viewer clicks on the gif image, they are then taken to a
>new page where a much larger jpeg image comes up so details may be viewed.
>It is a good idea to indicate next to the small gif images how large the jpeg
>image is so the person viewing your page can decide if they want to take the
>time to download an image that size.

Sounds like a plan, Stan...er, Pam. :)

>Book arts people do have a lot of good Web pages.  I've learned a lot and
>thank everyone for the time they have taken to make them.

And just for good measure:  me too!

Ron :)

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                       P  S  Y  M  O  N  ?  ?  ?  ?
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