Relative Image Urls in Posts are starting from root – Not from WordPress Address (URL) at General Settings

you should use this instead:

<img src="https://wordpress.stackexchange.com/questions/162608/<?php echo site_url();?>"https://wordpress.stackexchange.com/wp-content/themes/twentytwelve/...png">  

You’ve installed your wordpress in a abc.com/wordpress folder.
So when you use the backslash you are refering to the root of your domain, instead of the folder were you’ve installed your WP.

Hope that is helps.
Cheers