1. A method for providing input to a computing system including a touch sensitive surface, the method comprising: obtaining a sequence of proximity images of a set of one or more contacts, wherein each of the contacts corresponds to a touch object on or near the surface, the proximity images including proximity information of each contact at different times, wherein each contact appears in each of the proximity images; determining a first proximity of each contact based on a first proximity image of the sequence of proximity images; determining a second proximity of each contact based on a second proximity image of the sequence of proximity images, the second proximity image occurring after the first proximity image; calculating, based on the first and second proximities, a proximity change between the first proximity image and the second proximity image of each of one or more of the contacts, the proximity change including an indication of a motion of a first contact of the set of the one or more contacts; and providing, based on the one or more proximity changes, input to the computing system, wherein providing the input to the computing system includes modifying the motion of the first contact to generate a modified motion of the first contact, the modified motion of the first contact different than the motion of the first contact indicated by the proximity change.