I would like to know how I detect a image from a webpage. I want a code that if I want to share something on facebook the image from the page where I am at that time, automatically detect.
example:
<meta property="og:image" content="http://www.geturl.thedoctorofhouse.com/audi_a3_2.jpg" />
What should I do with the og:image content?
Yes, that looks correct - content should contain the url to the image that you want used.
You can check how the page metadata is interpreted by using the linter tool provided by Facebook