According to an embodiment of the present invention, when image data is output from an image forming apparatus, even if the specified sheet feeding unit is changed, an image positional shift function can be utilized. In an image processing apparatus, a factor according to which readjustment may be provided is generated, such as switching of sheet feeding trays or rotation of an image. In this case, the image processing apparatus can transmit a readjustment request to an external controller. The external controller receiving the readjustment request from the image processing apparatus changes the adjustment value and carries out a RIP processing again. Then, the external controller can re-transmit the image data subjected to the RIP processing to the image processing apparatus.