An image processing device comprising: a character configuration analysis unit configured to calculate, by utilizing scan data obtained by a scan of a document including a natural image in accordance with a specific optical resolution, the character configuration index value indicating size of the smallest character included in the document; a judging unit configured to judge, by utilizing the character configuration index value, whether a document fineness index value should be calculated, the document fineness index value being calculated based on the proportion of edge pixels among the scan data; wherein it is judged that the document fineness index value should be calculated in a case where the size of the smallest character indicated by the character configuration index value is equal to or more than a predetermined value, and it is judged that the document fineness index value should not be calculated in a case where the size of the smallest character indicated by the character configuration index value is less than the predetermined value; a document fineness analysis unit configured to calculate, by utilizing the scan data, the document fineness index value in a case where it is judged that the document fineness index value should be calculated by the judging unit, and not calculate the document fineness index value in a case where it is judged that the document fineness index value should not be calculated by the judging unit; an output resolution determination unit configured to set a first value as an output resolution by utilizing both the character configuration index value and the document fineness index value in a case where it is judged that the document fineness index value should be calculated, the output resolution being a resolution for image data set the output resolution to the same value as the specific optical resolution a conversion unit configured to convert the scan data indicating the specific optical resolution into resized image data according to the set output resolution, the resized image data having the set output resolution in a case where the output resolution is not identical to the specific optical resolution; and a creation unit configured to create a file including the resized image data having the set output resolution. a character configuration analysis unit configured to calculate, by utilizing scan data obtained by a scan of a document including a natural image in accordance with a specific optical resolution, the character configuration index value indicating size of the smallest character included in the document; a judging unit configured to judge, by utilizing the character configuration index value, whether a document fineness index value should be calculated, the document fineness index value being calculated based on the proportion of edge pixels among the scan data; wherein it is judged that the document fineness index value should be calculated in a case where the size of the smallest character indicated by the character configuration index value is equal to or more than a predetermined value, and it is judged that the document fineness index value should not be calculated in a case where the size of the smallest character indicated by the character configuration index value is less than the predetermined value;