1. A computer-implemented method for gray balance calibration in an image printing system, wherein the method is implemented in a computer system comprising one or more processors configured to execute one or more computer program modules, the method comprising: (a) printing, using a print engine, a reference test pattern consisting essentially of black marking medium; (b) sensing, using a sensor, the reference test pattern to obtain a reference image data, the reference image data being a function of the black marking medium; (c) printing, using the print engine, a second test pattern comprising a combination of marking mediums of different colors, other than the color black, available on the image printing system to simulate the black marking medium; (d) sensing, using the sensor, the second test pattern to obtain a second image data, the second image data being a function of the combination of marking mediums; (e) obtaining second intensity profiles using the second image data and reference intensity profiles using the reference image data; and (f) determining a difference between the reference intensity profiles and the second intensity profiles to obtain an intensity correction offset for gray balance calibration in the image printing system.