1. An image forming apparatus with a copy function that, after receiving a copy instruction, reads image data from a manuscript, and prints the read image data on printing paper according to set printing conditions; the image forming apparatus comprising: a character extracing unit that extracts characters from each of a plurality of different locations in the image data; and a line width judgment unit that determines whether or not the manuscript is pencil writing by comparing line widths of the characters that were extracted by the character extracting unit.