A method of data transformation including receiving a selection of an input structure, the input structure having a plurality of items, transforming each item in the input structure into a node, and applying a structure map to each node to produce a plurality of output nodes. An elastic chest band has front and back sections. Light is radiated to the reading position before the document is transported thereto while displacing the illumination unit in the same direction as a displacement direction of the illumination unit at a time of performing shading correction.