Getting the Width and Height of Dynamically Loaded Images?

Question

Possible Duplicate:
How to get image size (height & width) using javascript?

I'm dynamically loading different images with different dimensions.

<img src="A.png" alt="" />
<img src="B.png" alt="" />
<img src="C.png" alt="" />

How can I obtain the width and height of an image using JavaScript ?

I want to check the width of an image. For example:

if ( (width || height) < 200px) i want to double the size of image.

Thanks in advance.