[Reading] Lazy Snapping

This paper presents "Lazy Snapping", an interactive image cutout tool, also a novel coarse-to-fine UI design for image cutout. The task in image cutout is in specifying which parts of the image are "foreground" (the part you want to cut out) and which belong to the background.

Lazy Snapping consists of two steps, both are formulated as a graph cut problem:
(1) a quick object marking step
Object marking (at a coarse scale) specifies the object of interest by a few marking lines. This step is intuitive and quick for object context specification. An efficient graph cut algorithm is proposed by employing pre-computed over-segmentation so that the marking UI can provide instant visual feedback for users.
(2) a simple boundary editing step
Boundary editing (at a finer scale or on the zoomed-in image) allows the user to edit the object boundary by simply clicking and dragging polygon vertices, and use the polygon locations as soft constraints to improve snapping results around ambiguous or low contrast edges. This step is easy and efficient for accurate boundary control.