match image with Selenium2

Question

Not sure if I'm even asking this question correctly, however, here goes.

I'm looking at validating images in an automation suite that I just started. I am currently validating the location via XPath and if the image is there by ensuring that the URI matches a predefined string while checking to ensure that the image is returning either 200 or 304. Is there any way to actually match the image however (I was kind of thinking file size, but there may be a better way).
I think that anyone who works on applications where code and content are handled by seperate teams will understand the reason for this question.

Answer 1

For image comparison I could suggest to use - captureScreenshotToString. So you could keep one copy as reference point while other captured run time and then comparing it with already saved copy. But as you said it is not "great practice programmatically."... Also you would have to simulate selenium 1 to use captureScreenshotToString api from selenium 2. For more on this look here - http://seleniumhq.org/docs/03_webdriver.html#emulating-selenium-rc

Answer 2

SIKULI is a visual technology to automate and test graphical user interfaces (GUI) using images (screenshots). It stores the elements it comes across on the page in the form of bitmaps. It can be used for testing/comparison of images. Find more at http://sikuli.org/