Patent ID: 8369731

Claim:
An image forming apparatus, comprising: a charge fee counter unit including: a color counter configured to count a number of sheets to be printed in a full-color printing mode to generate a first counter value; a monochrome counter configured to count a number of sheets to be printed in a monochrome printing mode to generate a second counter value; and an economical counter configured to count a number of sheets to be printed in an economical printing mode to generate a third counter value, wherein the economical printing mode causes the image forming apparatus to form an image with colorant having a number of colors that is less than a number of colors used for the full-color printing mode or with colorant having an amount less than an amount of colorant used for a printing mode in which the economical printing mode is not set; and a counter processor configured to obtain selected one of: a total counter value of the color counter based on the first counter value and the third counter value; and a total counter value of the monochrome counter based on the second counter value and the third counter value, wherein the counter processor obtains the total counter value of the color counter by multiplying the third counter value with a weighting factor to generate a weighted third counter value and subtracting the weighted third counter value from the first counter value, the total counter value of the color counter being used for determination of a charge fee of the image forming apparatus based on a unit charge fee previously set for the full-color printing mode, and the counter processor obtains the total counter value of the monochrome counter by multiplying the third counter value with a weighting factor to generate a weighted third counter value and adding the weighted third counter value to the second counter value, the total counter value of the monochrome counter being used for determination of a charge fee of the image forming apparatus based on a unit charge fee previously set for the monochrome printing mode.