1. A method for digital image stabilization, applicable to an image sequence, wherein the image sequence comprises a plurality of images conforming to a pixel depth, the method comprising: dividing a current image into a plurality of target blocks, and defining a search area corresponding to each of the target blocks in a previous image; defining K Gray-coded bit-planes based on a plurality of raw bit-planes corresponding to the current image and defining K Gray-coded bit-planes based on a plurality of raw bit-planes corresponding to the previous image, wherein K is a positive integer smaller than the pixel depth; comparing each of the target blocks and the corresponding search area thereof which are respectively formed by interlacing the corresponding K Gray-coded bit-planes, so as to obtain a plurality of correlation measures between each of the target blocks and the corresponding search area thereof; estimating a global motion vector indicating a motion of the current image relative to the previous image, based on an average value and a minimum value of the correlation measures of each of the target blocks; and calculating an accumulated motion vector reflecting a motion of the image sequence based on the global motion vector, and determining an output image from the current image based on the accumulated motion vector.