Compression question / problem

Alex Tweedly alex at tweedly.net
Wed Jan 12 13:49:10 EST 2005


Richard Miller wrote:

> Looking for the simplest and quickest solution to a compression 
> problem. The goal is to take 50 jpeg images (highly compressed) 
> starting on a Mac, move them to our directory on a hosted web server, 
> then have them downloaded and displayed on a Windows XP machine. 
> Transmission time (over the Internet) is a very big factor here.
>
> Here's what we've done so far:
>
> 1. Started with 50 jpeg images.
> 2. Put them into 50 custom properties of a holding stack.
> 3. Compressed the stack using the RR compress command.
> 4. Decompressed that stack using the decompress command.
> 5. Tried to open that stack, but it is always reported as corrupted.
> 6. The size of the decompressed stack is ALMOST the same as the 
> original stack, but a few bytes short.
>
> Also tried this:
>
> 1. Took one of these jpeg images.
> 2. Compressed it with RR compress command.
> 3. Decompressed it.
> 4. Tried to open it. It is always corrupt.
> 5. The size of the decompressed file is the same as the original file 
> size, but in looking at the data in TextEdit, it is readily seen a few 
> characters have shifted places in the first few lines.
>
> Suggestions? What's going on here? Thanks.

The overall description mentioned various different machines - but the 
step-by-step didn't. Is this testing all on one machine ?
I tried this script

on mouseUp
  local t, t1
  put URL ("binfile:d:/Our Documents/Alex/RunRev/Photo/IMGP0633.JPG") into t
  put the number of chars in t after msg
  put compress( t ) into t1
  put "  " & the number of chars in t1 after msg
  put decompress(t1) into t
  put "  " & the number of chars in t & cr after msg
  put t into  URL ("binfile:d:/Our 
Documents/Alex/RunRev/Photo/IMGP0633-x.JPG")
end mouseUp

and verified that it the output JPG works fine. Might be worth you 
trying it (with suitable file name, of course :-) and then narrowing in 
on any differences between it and your own test script.

-- Alex.


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