A different window is the simplest way to do this. Define a layout where the container field fills the body of the layout from top to bottom and left to right. Set top, bottom, left and right resize anchors. In data formatting on the Inspector's data tab set the container field's image to reduce or enlarge and keep the maintain proportions options selected.
You can now use a script with New window followed by go to layout open up this layout in a new window. If the user clicks and drags an edge or corner of the window to resize it, the image will scale to fit the size change.
Take a look at the Product Catalog starter solution.