Well the first thing to say is that SP filters are exactly the same as WP filters and used in the same way. So if you are unsure about them then you can read up all about them on the WP codex. They are VERY easy to use.
The filter in SP you would need is called ‘sph_display_post_content_pre_filter‘. This passes in the $content variable and at the end of the filter you need to return the $content massaged appropriately.
But the other thing you need is information about the current user so you will need to decide what data to use as a test on whether you need to parse the content and change it or not.
Globalise the variable $spThisUser. This will ALWAYS return a data object pertaining to the current user making the request. To see what data is available in $spThisUser go to the forum admin > Toolbox > Data Inspector and turn on the option to display it. Next time you run a forum page you will see the available data.
So you should end up with something like:
add_filter('sph_display_post_content_pre_filter', 'my_parse_function');
function my_parse_function($content) {
global $spThisUser;
if($spThisUser->XXXXX == YYYYY) {
$content = ZZZZZ;
}
return $content;
}
where XXXXX is the data item you need to check against YYYYY and ZZZZZ is the operation you want to perrorm on the $content – probably some regex to strip images.
Some notes: This will only effect display. It will not change the content of saved data. The spFunctions.php file in the SP theme templates folder is the best place for this. As always we recommend that you create your own SP theme so that any customisation is not lost during a future update. (http://codex.simple-press.com/codex/themes/theme-basics/creating-a-theme/)