How to resize an image in pure HTML CSS while keeping its proportions

Question

How can I crop an image while maintaining its dimensions and using HTML/CSS alone resizing (i.e., no server code)? I want to crop it to the set height if the height is more than a certain amount and resize it to a specific width while maintaining the proportions.

Actually, I have some server code that I can use to accomplish that, but I don't want to. Using a different file reference and referring to the image as would be implied. On the same page where the image is displayed, I need to process it.

The fact that I have to submit the image header in order for nothing else on the page to display "bothers" me.

Is there a means to carry out such an action? perhaps from HTML/CSS only?:P

With the exception of the "crop" feature, I created a function that performs something similar and only returns width="" and height="." I use it as img src="image.jpg" resize("image.jpg") />, but I'm not sure how to achieve that crop.

Thanks