Adding Criteria to check for available cache

What steps will reproduce the problem?
1.running 
http://www.burnerbyte.com/wp-content/themes/DeepFocus/timthumb.php?src=http://ww
w.burnerbyte.com/wp-content/uploads/2010/12/IMG_5645-copy.jpg&amp;h=185&amp;w=18
5&amp;zc=1&amp;q=90
for example.

What is the expected output? What do you see instead?
I would like to have the engine to use previously generated image rather than 
regenerate a new one

What version of the product are you using? On what operating system?
saw this in my script 
define ('VERSION', '1.15');                 // version number (to force a cache refresh)

Please provide any additional information below.
Thanks for providing this code and enable me to generate any image size on the 
fly and enhance user experience for transfering much smaller image over to the 
browser.
However, the common issue face is that the image generation into the cache will 
be hogging up the CPU resources. Is there a solution to check for the image 
available in the cache before generating? Cos the image that i use is all the 
time the same and by reuse the image will save alot of CPU resources as I will 
only need to generate this 1 time and use this multiple time.

Thanks.

Hope that I able to get help from this brilliant team ^_^

Original issue reported on code.google.com by bytesur...@gmail.com on 22 Apr 2011 at 12:04

oseawey / timthumb

Adding Criteria to check for available cache #181