Plugin to Trim Posts and images (everything except links)

I need a plugin which can trim posts in the WordPress Loop to a certain character limit (e.g. 500 characters) and not trim the HTML (e.g. link I don’t want HTML like that cut in half.

I also want to only include certain HTML elements, such as links but not include any other HTML element (like images)

Is there any plugin which can do that?

Thanks for any tips.