You need to think about how a web page and images relate to
each other.
ColdFusion does not handle the image, it handles the HTML
that is sent
to the client browser. The client browser then parses the
html and sees
an image tag. The browser then makes a new request to the
server for
the image and, in a default configuration, the web server
would see that
an image is not a ColdFusion template and just attempt to
grab the image
from the file system and return it to the client.
So that gives you two options to attempt this functionality.
One you
can have CF check the file system {<cffile...> for the
image before it
builds the <img...> tag in the original request and
send different
<img...> tags based on that file check. This is very
costly in IO and
processing and would not scale well, but it is quick and easy
to build.
You can create an image.cfm file. You put this file into the
'scr'
property of all your <img...> tags with a parameter of
what image to
show. Something like <img
src="myImage.cfm?file="aPicture.jpg">. Then
in the image.cfm file you then retrieve the requested image
and return
it using <cfheader...> tags and a <cfconent...>
tag to properly return
the binary image. This is still a fairly high IO process, but
since it
is isolated in separate requests, the user perception of the
page
loading is better then the first. Especially if you properly
build you
image tags with alt, width and height properties so that the
browser can
lay out the page while retrieving the images.
