1. An image forming apparatus, comprising: a specific graphic form storage section configured to store a visual image of a specific graphic form and attribute information specific to the specific graphic form as a reference image and reference attribute information, respectively; an image determination section configured to: determine at least one of (i) whether or not an image matching with the reference image is included in target data and (ii) whether or not an image having the reference attribute information is included in the target data; and detect the image identified through the determination as an image corresponding to the specific graphic form; and a color conversion processing section configured to perform specific color conversion processing for the image corresponding to the specific graphic form.