Provided is an image processing apparatus that can accurately and efficiently reduce color unevenness that occurs in a color image, which is formed by color mixture of a plurality of different types of inks, due to a variation in ejection characteristic among nozzles. For a selected trace, first several digital values obtained by detecting the selected trace are compared with a threshold value to identify whether the selected trace is useful or not, and if the selected trace is identified useless, an abort signal is triggered to abort detection of the selected trace. If a transponder of the said first type is found, the characteristics of the various transponders of first or of second type which are referenced in the said signalling table are extracted from its signalling table and the services associated with the various transponders are installed. The spring is positioned outside the holder and provides a force to the supporting shaft for pushing the contact image sensor upwardly.