Image Slicing was Re: [oclug]for the mac / linux fans

[Shad Young]

On Tue, 2003-01-14 at 01:46, Brad Barnett wrote:


> 
> [endbit.jpg][endbit.jpg][endbit.jpg]  
> [endbit.jpg][endbit.jpg][endbit.jpg]
> [endbit.jpg][endbit.jpg][endbit.jpg] <bigmiddlepart> <clone_of_left_side>
> [endbit.jpg][endbit.jpg][endbit.jpg]
> [endbit.jpg][endbit.jpg][endbit.jpg]
> [endbit.jpg][endbit.jpg][endbit.jpg]
> 
> Wow!  Suddenly you've saved tons upon tons of filesize, right!  Let's look
> at this in more detail!  Instead of one image, you have one center part,
> but the red ends have been chopped into 36 identical pieces, which only
> needs to be fetched from the server once!  A savings?
> 
> Take a look at this image of the Canadian flag:
> 
> http://canflag.ptbcanadian.com/images/regular/311x150.jpg
> 
> -rw-r--r--    1 bbarnett bbarnett     4178 Jan 12 23:02 311x150.jpg
> 
> Now, using XV, I will take it, and crop a piece of the red ends, equal to
> 1/18th of the size.  This means that each end will represet the same as
> above.  Look however!  Part a is the small end bit that will be repeated,
> and part b is the middle "leaf" part of our flag.
> 
> -rw-r--r--    1 bbarnett bbarnett      743 Jan 12 23:10 311x150_a.jpg
> -rw-r--r--    1 bbarnett bbarnett     3224 Jan 12 23:11 311x150_b.jpg
> 
> --------------------------------------------------------------------
> 
> How do you find it difficult to understand that 3224+743= 3967, while the
> original image was 4178 bytes?  How do you find it difficult to
> understand, that the actual GET statement (with full path) to the web
> server, the extra IMG SRC and what not, actually makes the above spliced
> image MORE costly for bandwidth?  Repeating a red square 18 times per end,
> for a total of 36 times, doesn't save anything.  It costs you in terms of
> bandwidth, file handles on the server, and cpu usage on the client.


Wow all that and you still fail to understand that the rest of the image
is built out of cache and that the browser will not actually send a get
request for ever single img tag? I already admitted that memory usage is
increased, but that is client side and of minor consequence as bandwidth
is far more costly.

Shad

-- 
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"Fortune should have the arbitrant of one-half of our actions, but she
leaves the other half, or little less, to be governed by ourselves. 
- Machiavelli
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