Image scanner

An image scanner includes: a document table; a document cover; a light source; an image sensor; and a circuit configured to: acquire, as pre-reading black data, the line data that is generated by the image sensor in a state where the light source is turned off; after acquiring the pre-reading black data, acquire, as line image data, the line data that is generated by the image sensor in a state where light is emitted from the light source to an original document supported on the document table; after acquiring the line image data, acquire, as post-reading black data, the line data that is generated by the image sensor in a state where the light source is turned off; determine black reference data based on the post-reading black data and the pre-reading black data; and perform black correction on the line image data based on the black reference data.