1. An image sensor, comprising: a pixel array having a plurality of pixels formed to maximize light sensing characteristic, the pixel array being configured to detect information on an external image; a timing controller for controlling an overall operation of the image sensor; an analog signal processor for converting an analog signal from the pixel array into a corresponding digital signal under control of the timing controller; a line memory for storing the digital signal in line unit; an image signal processor for processing a plurality of images by using the digital signal stored in the line memory so as to improve performance of the image sensor; and a scaler for receiving a scaling factor of a desired image size from the timing controller and calculating a scaling ratio so as to adjust an image size, and generating a corresponding row/column address and data and scaling the image stored in the line memory, whereby the image with the desired size is outputted.