1. An image sensor comprising: a timing controller for controlling an overall operation of the image sensor; a line memory for storing digital signals corresponding to a plurality of images; and a scaler for generating a row/column address by calculating a scaling ratio according to a scaling factor of a desired image size from the timing controller, to scale the corresponding image, wherein the corresponding image of the desired size is outputted through a pre-scaler and a post-scaler coupled to each other in the image sensor, and coupled to a scaling ratio generator, a timing controller and the line memory, and selectively executed according to the scaling ratio.