Flood Selection Tool

The following settings can be adjusted using a vertical tool slider:

Tolerance—sets the range of pixels affected when a pixel is tapped. For lower tolerance settings, pixels must be very close in value to the tapped pixel. For higher tolerance settings, pixel colour can vary widely from the tapped pixel.

The following settings can be adjusted from the context toolbar:

Mode—select from New, Add, Subtract, and Intersect.
Source—the source determines the layer(s) from which the pixels are sampled. Select from the pop-up menu.
Contiguous—when enabled, only selects a range of pixels within the same area. If disabled, similar pixel ranges will be selected even if they are separated and in different parts of the image.
Antialias—if this option is off (default), edge pixels are fully opaque, which may result in a ragged appearance. When selected, edge pixels are anti-aliased for a softer appearance better suited to compositing against a new background.
Refine—switches to the Refine Selection feature so you can more precisely set the edges of the selected region.

The four modes available from the context toolbar affect how your selection develops.

New—cancels all current selections and creates a new selection.
Add—adds areas to the current selection. If there is no selection in place, a new selection will be created.
Subtract—removes areas from the current selection.
Intersect—a new selection area is created from the overlap between the newly added selection area and the current selection.