1. A portable electronic device, comprising: a touch screen display; one or more processors; memory; and one or more programs, wherein the one or more programs are stored in the memory and configured to be executed by the one or more processors, the one or more programs including instructions for: generating down sampled data for a graphical object; displaying the graphical object on the touch screen display at a first magnification level using the down sampled data; while displaying the graphical object on the touch screen display using the down sampled data, detecting a multi-touch input associated with the graphical object; in response to detecting the multi-touch input associated with the graphical object, performing a zoom-in operation on the graphical object, wherein the zoom-in operation on the graphical object is a non-linear function of a gesture made by the multi-touch input; while performing the zoom-in operation on the graphical object, displaying changes to the graphical object caused by the zoom-in operation in real time using the down sampled data, the changes including displaying the graphical object at a second magnification level and a first resolution using the down sampled data, wherein the second magnification level is higher than the first magnification level; and while displaying the graphical object at the second magnification level and the first resolution using the down sampled data after the zoom-in operation, replacing the display of the graphical object at the second magnification level and the first resolution using the down sampled data with a display of the graphical object at the second magnification level and a second resolution using resampled data, wherein the second resolution is higher than the first resolution.