The issue is that there are two different namespaces. The one used within the server OS and the one that the browser sees.

In the past I have created a "Dynamic Images" directory (say ~/web_pages/tmp) which is mapped by Apache (say to to "//dyn_images/"). Then the file I create is ~/web_pages/tmp/2006Sep09_01.jpg and the <img> refers to "/dyn_images/2006Sep09_01.jpg"

The Alias directive in Apache is what you need.