1. A non-transitory machine readable medium storing a program which when executed by at least one processing unit provides a graphical user interface (GUI), the GUI comprising: a display area for displaying an image comprising a plurality of pixels; a selectable masking tool for displaying in the display area an adjustable closed curve to identify a region in the image to apply a color correction operation, the selectable masking tool comprising a selectable control for modifying the adjustable closed curve through a range of elliptical shapes that ranges from a pure ellipse to an approximate rectangle; and a selectable GUI item for applying the color correction operation based on the selectable masking tool.