A current thread asks about monitor resolutions so that images could be
sent to fit most monitors. IMO, that is not a good idea. Your image file
should be the original, if at all possible. If you do think that
resizing it is desirable, reduce it, don't enlarge it. See below for the
reasons why. And reduce it as little as possible.

The display software can and will take care of resizing the image
display if that's what the end user wants. But that resizing of the
display will not change the image file itself.

IMO, the only reason for resizing an image is to reduce the file size,
to make transmission via the internet faster. But in doing this, you
will permanently lose image information, so it's a better idea to
compress the image, not resize it. Compressing cause some information
loss, but much less than resizing. (Cameras do a "lossless" compression,
which means that you can compress the image another 50% or so with no
noticeable loss of quality at the usual display or printing sizes.)

I think it might be a good idea to post two sizes of picture. 800x600
will give you a nice small files size, around 200K, so that the people
on dial-up can download it in a reasonable time. Files around 1200x800
or larger (files size 400K or more) are suitable for people on broadband.

Tech talk (you've been warned ;-))

There are two issues he the actual image size, and the displayed
image size. They are by no means the same thing, although they are
related. Both are measured in pixels, but that is all they have in common.

For example, if your monitor is at 1280 x 1024 pixels, then any image
smaller than this can be displayed as is. An actual 800x600 image will
display in the center of the display area with more or less white (or
black) space around it.

The smaller image could be expanded to fit the larger display area. The
display software does this by replacing blocks of pixels by larger
blocks of pixels. In doing this, it will distort some of the image
information, adding small detail where is none, for example. The effect
of this will be seen most obviously on diagonal lines, which will often
be turned into stair steps, called the jaggies. Better software will
smooth the jaggies, but there's a limit to what can be done.

OTOH, if the image is 1600x1200 pixels, the display software can reduce
the displayed image to 1280x1024. It does this by replacing groups of
pixels with smaller groups of pixels. This process loses some image
information, so that the displayed image will not have the same clarity
of small details, for example.

Most image viewers allow you to zoom in or out. This changes the
displayed image size.

In no case is the original image changed in any way.

When you resize the original image, the image processing software does
exactly what the display software does, but this time the changes are
permanent. The image file will be larger or smaller, depending on which
way you resized the image. In both cases, the image information will be
distorted. The smaller image will have less image information. Note that
you cannot recover this, it is permanently lost. The larger image will
have added false information. If you reduce an enlarged image, then some
of that false information will be retained (and you can't tell
beforehand what it will be.)

HTH

--


Wolf

"Don't believe everything you think." (Maxine)