product resizing with html?

[djangle]

Hello,

Basically in my product listing I would like the image to show on my page with a maximum width of 250 pix. I could define the image as below but it is giving a distorted image or if I have a tall narrow image it is enlarging the image.

<img src="[image1]" alt="[name]" name="large" width="250" border="0" align="middle" id="large" />

Is there a way to only resize if the width is above 250 pix and leave all others the same?

Basically I am wanting a third picture size between my thumbnail and large picture without needing to make a third size of all images in the file.

Thanks,
Donald