1. A method for segmenting contacts in a proximity image, the method comprising: obtaining a proximity image, the proximity image including a plurality of proximity values, each proximity value representing a measurement of touch object proximity at a location within a sensing area of a touch sensing surface, each location being associated with a first coordinate in a first dimension of the sensing surface and a second coordinate in a second dimension of the sensing surface; locating a local maximum proximity value in the proximity image; and after locating the local maximum proximity value, determining a two-dimensional boundary of a contact, the boundary surrounding the local maximum proximity value, including a two-dimensional search that applies a first boundary test including comparing a first proximity value to a second proximity value adjacent to the first proximity value in the first dimension, comparing the first proximity value to a third proximity value adjacent to the first proximity value in the second dimension, and comparing the third proximity value to a fourth proximity value adjacent to the third proximity value in the first dimension.