1. An image reading apparatus, comprising: a first reading section that reads a document; a second reading section that reads a document; a document image storing section that stores a first document image generated from the document being read by the first reading section and that stores a second document image generated from the document being read by the second reading section; an output controlling section that controls outputting the first document image and the second document image; a distinguishing pattern storing section that stores information about a distinguishing pattern which represents a prohibition of output performed by the output controlling section; a determining section that determines whether the first document image and the second document image contain the distinguishing pattern or not; a standard chart image storing section that stores a first standard chart image generated from a standard chart being read by the first reading section and that stores a second standard chart image generated from a standard chart being read by the second reading section; a sample data storing section that stores sample data; a first calculating section calculates a first correction parameter from a comparison between the sample data and the first standard chart image; a second calculating section that calculates a second correction parameter from a comparison between the sample data and the second standard chart image, wherein the determining section determines, on the basis of the first correction parameter, the first document image and the information about the distinguishing pattern, whether the first document image contains the distinguishing pattern or not, the determining section determines, on the basis of the second correction parameter, the second document image and the information about the distinguishing pattern, whether the second document image contains the distinguishing pattern or not, and the output controlling section prohibits outputting an image on which the determining section has determined that the distinguishing pattern is contained;and a first setting section that sets a first distinctive color range based on the first correction parameter and the information stored by the distinguishing pattern storing section, wherein the first distinctive color range is configured with thresholds defining ranges of plural color parameter values, the determining section determines on the basis of the first distinctive color range whether the first document image contains the distinguishing pattern or not, and further on the basis of the first distinctive color range, the determining section determines whether the second document image contains the distinguishing pattern or not.