There is provided a data processing device that includes an obtaining unit that obtains a first image data set, a second image data set generated by reading an image formed using the first image data set, and a property data set indicating the properties of a recording medium on which the image is to be reproduced. The data processing device also includes a specifying unit that determines a threshold for a density difference between the first image data set and the second image data set, wherein the threshold depends on the property data set. The specifying unit also determines an error area where the density difference between images expressed by the first and second image data sets is equal to or greater than the threshold.