Resize and center images

Website is [login to view URL] When you click on a post from the homepage and it opens, the image is sometimes too big and doesn't fit. I need you to set a maximum height for all images so that, if they are bigger, they get resized to match that maximum height (proportions have to remain the same, of course). I also need you to center the images (right now they are aligned on top, I need you to center them vertically and horizontally). Beware that there are two viewing options for posts: one is when you open a post from the homepage -> this is what you're working with. The other one is when you open a post directly via its url and you must not touch that. It's actually a very easy job so I'm not taking any big bids for this one.