How to get featured image from Wordpress?

Help me better understand how WordPress handles images.

• I need to better understand how WordPress works with images, how they load onto a page and the best way to automate the process to keep a WordPress self-hosted site running fast.. I don't understand how the WordPress deals with images out of the box. The site I'm working on has images at the top of various pages, and thumbnails (featured images). In order to optimize these images, we uploaded some test content, and then using a screen ruler, measured the size of the main image and the featured image in pixels, and then using photoshop, created .jpg images that are the exact right size and compression level for the way the images are displayed. I know that this method works in the sense of the images are compressed well, and the pages load fast, but I also know it's inefficient and not something the site owner is going to want to do. I also know that WordPress automatically re-sizes images, but not necessarily to the exact sizes that will be used. What's the best way to automatically handle image re-sizing, compression, and cropping for their displayed output? (I also don't like how automated image re-sizing also crops images badly). I've seen the site owner happily upload 20mb files (for images that should be displayed at about 5KB) so I need a simple and good way to show them the path forward without my complicated process. I also wonder if just having 20mb files in their media library is somehow affecting site load times.

• Answer:

  Have you read through http://codex.wordpress.org/Using_Images in the WordPress Codex? You might also be interested in the http://codex.wordpress.org/Function_Reference/add_image_size function, which lets you add more image options, so WordPress will resize to specific dimensions (and crop if necessary).