1. An image processing method comprising the steps of: inputting image data in an information processing device; analyzing, by the information processing device, the input image data to determine whether a ground pattern is detected in the input image data; when it is determined that a ground pattern is detected in the input image data, calculating a threshold value used for detecting the ground pattern and transmitting the threshold value used for detecting the ground pattern to an external device, wherein the: threshold value used for detecting the ground pattern is calculated based on a number of lines and density of the ground pattern; using the information processing device to calculate parameters for modifying the ground pattern so that the ground pattern is visually distinguishable from other portions of the image data; and transmitting the parameters to the external device so that the external device can use the parameters to modify the ground pattern.