1. An image processing method for determining a motion vector of a covered/uncovered area of an interpolated picture when a picture interpolation is performed, the interpolated picture including a plurality of blocks, the image processing method comprising: generating a first motion vector and a second motion vector of a block within the interpolated picture; according to the first and second motion vectors, determining which one of the covered and uncovered areas the block is located in and calculating a reference vector; and determining a motion vector of the block according to the reference vector; wherein the reference vector is obtained from a vector calculation of the first and second motion vectors using a principle of similar triangles, and the step of generating the first motion vector and the second motion vector of the block within the interpolated picture comprises: calculating a data curve according to an original motion vector of the block and a plurality of original motion vectors of a plurality of neighboring blocks; and determining the first motion vector and the second motion vector of the block according to the data curve, wherein the first motion vector corresponds to a minimum value to the left of a maximum value of the data curve, and the second motion vector corresponds to a minimum value to the right of the maximum value of the data curve.