Username Image , Limit the Image size

[Psyd0x]

I made a simple username image custom field and i want to limit the image link to 100x150 pixels maximum how can i do it?

The field is in postbit_lagacy, here is the code:

						<vb:if condition="$post['field6']">
							<img src="{vb:raw post.field6}" border="0" /></a>
						<vb:else />
							{vb:raw memberaction_dropdown}</a>
						</vb:if></vb:if>

How can I limit the size?