Patent ID: 8588632

Claim:
An information processor comprising: a storage unit that stores a first coefficient, which is preset on the basis of the relationship between a water content of a sheet of paper and a signal output from a signal output unit on the basis of the water content when a sheet of paper having each characteristic has the water content, in correspondence with the characteristics; a first acquisition unit that acquires a first signal output from the signal output unit on the basis of the water content of a first sheet of paper not having a first image formed thereon; a second acquisition unit that acquires a second signal output from the signal output unit on the basis of the water content of the first sheet of paper which has the first image formed on a first surface thereof and which is heated to fix the first image; a determination unit that determines the characteristic of the first sheet of paper; a first calculation unit that calculates a variation in water content of the first sheet of paper using the difference between the acquired first signal and the acquired second signal and the first coefficient stored in correspondence with the determined characteristic in the storage unit; and a second calculation unit that calculates an expansion and contraction ratio of the first sheet of paper using the variation in water content calculated by the first calculation unit.