image resizer wont work for this, the thumbnail would need to be a separate image tag for image resizer to be able to resize the iamge.
if you use this method, the only work around will be to resize the iamges manully in photo shop to crop them.
otherwise use a gallery script that allows for separate large and thumbnail images
in your image tag:
you need to set width and height:
<img src="image.jpg" width="200" height="300" />
that width and height is used by image resizer when creating the new image
you can apply image resizer to the image tag, or the surrounding div, either will work as long as the image has a width and height specified.