Image forming apparatus, method of correcting image magnification, and computer-readable recording medium

A method of correcting image magnification performed by an image forming apparatus that performs double-side printing, the method comprising:

• calculating, by an expansion/contraction ratio calculation unit, a value of a ratio of expansion or contraction of a printing medium at a time of printing a second surface of the printing medium as compared with that at a time of printing a first surface of the printing medium;
• causing, by a storage control unit, a storage unit to hold the calculated value of the ratio of expansion or contraction while updating the value every time a new value is calculated;
• obtaining, by a magnification correcting unit, a difference between a newly calculated value of the ratio of expansion or contraction and a value that has been held by the storage unit until the new value is calculated, and determines whether or not the difference is within a predetermined range;
• and
• correcting, by a magnification correcting unit, magnification of an image to be printed on the second surface using the newly calculated value of the ratio of expansion or contraction when the difference is within the predetermined range, and correcting the magnification of the image to be printed on the second surface using a different value than the newly calculated value of the ratio of expansion or contraction when the difference exceeds the predetermined range.

A non-transitory computer-readable recording medium that contains a computer program for causing an image forming apparatus that performs double-side printing to implement:

• a function of an expansion/contraction ratio calculation unit that calculates a value of a ratio of expansion or contraction of a printing medium at a time of printing a second surface as compared with that at a time of printing a first surface;
• a function of a storage control unit that causes a storage unit to hold the calculated value of the ratio of expansion or contraction while updating the value every time a new value is calculated;
• and
• a function of a magnification correcting unit that obtains a difference between a newly calculated value of the ratio of expansion or contraction and a value that has been held by the storage unit until the new value is calculated, and determines whether or not the difference is within a predetermined range, corrects magnification of an image to be printed on the second surface using the newly calculated value of the ratio of expansion or contraction when the difference is within the predetermined range, and corrects the magnification of the image to be printed on the second surface using a different value than the newly calculated value of the ratio of expansion or contraction when the difference exceeds the predetermined range.