Resize from the nearest screen edge

[dgileadi]

The app currently resizes based on the bottom-left corner of its window, expanding or contracting the top and right sides of its window. This PR changes it to resize based on the corner of the screen that the image is nearest to. So for example if it's nearest to the top right of the screen then the bottom and left sides of its window will expand or contract as the image resizes, and so on.