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_gail
Posts: 2876
From: So FL
Status: offline
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Caching Images - 2/22/2002 12:47:11
I've been reading the excellent article by abbeyvet "Designing Fast Loading Sites." In it she recommends caching images by changing the size of the image to 1x1 pixels and placing the 1x1 on another page a user will visit first. The image will be cached before a user gets to the page where the full sized image (or thumbnail) is placed.
I tried this and here's what happens. Say an jpeg takes 10 seconds to load. When I reduce the image to 1x1 pixels, yes it becomes invisible, but the load time does not appear to change. So I'm reducing the time it takes to load on one page but increasing the time on another page.
Question: am I doing something wrong or does this technique truely not reduce download time?
Abbeyvet also suggests placing the 1x1 "below the footer table so that it will not affect loading of the page in which it is placed."
Wow! Is this really true?! I've just never heard this before and am pleased to learn it!
Thanks...gail
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abbeyvet
Posts: 5095
From: Kilkenny Ireland
Status: offline
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RE: Caching Images - 2/22/2002 13:06:46
I suppose I shuld clarify :)
Yes the 1x1 image stays the same file size as the eventual image. That is actually the whole point - you are preloading into cache the entire eventual image.
Where you place this image on the page is ]vital
If you put it into any of the tables that do up to making the page in which the 1x1 image is included then yes, it will slow the loading of that page. In fact it will slow the loading of that page no matter where you put it. BUT if you put it as the very last thing on the page, after your final table, then the inclreased load time will not be noticable as the image will only start to load after the rest of the page is already loaded. An observant user might notice that the status bar showed something still loading, but the entire page will be visible so most either will not notice or not care.
It is easier to show than to explain in a way. Take a toddle over to this page: http://www.vectorpower.com/post_drivers.htm
Click for more details about Model 3 - which is a whopper of a machine and has a correspondingly large image. Keep an eye on the status bar as it is loading and you will see what I mean. The look at the source and right down at the end you will see this:
<p><img border="0" src="images/mod3lrg.jpg" width="1" height="1"></p>
That is loading the large image but I defy you to see it on the actual visible page. :)
Click on the image to throw up the large one though - up it pops instantly.
Of course some people will click for the large image before it has fully loaded, but it will have partially loaded and event hat will speed it up a bit. And many will read the text before they click for the image, long enough for the loading to occur.
Because it is not infallible this does not take away the need to optimize the images - these are made as small as I could get them but it was one of those occasions where large images really are required, and that is where techniques like this are really valuable.
Katherine
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www.inkkdesign.com
"Dogs have owners, cats have staff"
Meeeooow!
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_gail
Posts: 2876
From: So FL
Status: offline
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RE: Caching Images - 2/22/2002 13:24:36
Yes, checked it out, even on a 56 k modem. I'm going to try it out. Thanks for all the info!
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_gail
Posts: 2876
From: So FL
Status: offline
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RE: Caching Images - 2/22/2002 15:29:43
Oh, forgot to ask: Does this work best if there is at least one table on a page? The page I initially tested it on has no tables. It is also a frame page.
Edited by - Gail on 02/22/2002 15:48:18
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abbeyvet
Posts: 5095
From: Kilkenny Ireland
Status: offline
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RE: Caching Images - 2/22/2002 16:20:22
If there is no table just put it at the end of the page.
In a frames set up I would put in on the main page - it shouldn't matter whether it is framed or not.
Katherine
++++++++++++++++++++++++
www.inkkdesign.com
"Dogs have owners, cats have staff"
Meeeooow!
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