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Re: CF: images & caching.
On Mar 8, 1:26pm, William Tanksley wrote:
> Subject: Re: CF: images & caching.
> On Thu, 5 Mar 1998, Mark Wedel wrote:
>
> Words cannot express the difference. It's that bad. XPM doesn't even
> pretend to try to be small.
It would be pretty easy to convert some images to PNG and do a space
comparison should be easy to do.
I don't pretend to suggest that XPM is small (note however that if you are
at the end of a compressible link, XPM will likely compress nicely, while
precompressed images will remain roughly the same size, so overall transmission
speed may not be as far off as just the raw sizes suggest)
> XPM isn't _really_ a native format to anything; it's just standard. So
> any such comparisons...
But on X, XPM gets converted into a native format, and then all further
operations are done in this converted native form.
From what is sounds like, to use the better features of PNG, it
remains in PNG format where you do the merging/transparency/etc, and then
after all that is done, you convert to native form and draw it.
> Anyhow, my point is that the sheer size of XPMs relative to any logical
> standard makes them slower to convert to and from visible format, if only
> by loading time. PNGs also have a disadvantage is they're used in
> compressed format, but that's why PNG is never _used_ that way (only
> transmitted).
Size of image should have nothing to do with conversion speed (or very
little) - it only really relates to transmission speed.
All images are 24x24 in size, so you are converting the same number
of pixels no matter what format. Something like gif might get you the
image faster, but be slower than XPM on conversion to native form, being
you need to do decompression where as with XPM you don't.
However, with the speed of current computers, I don't think the conversion
speed/efficiency of the images is all that relevant.
--
-- Mark Wedel
mark@pyramid.com
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