1. A non-transitory machine readable medium storing a program which when executed by at least one processing unit defines a border for an image, the program comprising sets of instructions for: receiving a single continuous input to move a location indicator over an image; defining a border for the image along a series of reference points located at edges of the image along the movement of the location indicator, the border for use in defining a region of interest of the image, wherein the distance between two successive reference points is based on a speed of the location indicator movement between the two successive reference points while drawing the border; and when the single continuous input moves the location indicator over a location on the border between a first reference point and a second successive reference point, deleting a previously defined first section of the border from the first reference point to an ending point of the border while leaving a previously defined second section of the border intact from the first reference point to a starting point of the border.