A method and apparatus may include aligning a reference image and an input image through ROI-based image alignment; detecting an ROI associated with an incompletely aligned region in the aligned image; and blending the aligned reference image and input image by using a plurality of weights which are attenuated according to a spatial distance from a boundary of the detected ROI. In addition, the method and apparatus may include aligning a reference image and an input image through image alignment based on an nth region of interest (ROI) which is detected at a previous stage; detecting another ROI associated with an incompletely aligned region in the aligned image; and blending the aligned image in the other ROI and an (n+1)th blended image, which is input from a next stage, in a region outside the other ROI, and outputting the last blended image to the previous stage.