1. An image reading apparatus comprising: at least three line sensors mutually spaced in a sub scanning direction to scan an original in the sub scanning direction, wherein outputs of the at least three line sensors are composited together to form an image of the original; a platen arranged between the original and said at least three line sensors; a mover moving said platen at a rate relative to said at least three line sensors, said rate being different from a rate of movement of the original relative to said at least three line sensors; an extractor configured to extract a feature pixel having a predetermined feature from any of at least three data output corresponding to said at least three line sensors; and a detector configured to identify a noise pixel by comparing said at least three data corresponding to a single location on the original and identifying the feature pixel as noise pixel if said feature pixel is detected for one of said at least three data and is not detected as a feature pixel for each of the other at least three data, wherein said extractor includes a region extractor extracting a region having a limited variation in lightness and a difference from a neighboring region in lightness of at least a predetermined value, and extracts as said feature pixel a pixel included in a region extracted.