1. An image estimation apparatus comprising: a forming unit that forms a reference frame with a size determined uniquely in accordance with a size of a recording region where an image is recorded; and an estimating unit that estimates a type of a single image based on a size of a bounding frame around the single image and the size of the reference frame formed by the forming unit, the single image being a target of type inference in an image contained in a designation region in a recording region image which is an image indicating the recording region where an image is recorded, wherein the estimating unit estimates that the single image as the target of type inference contained in the bounding frame is a character image expressing a character when the bounding frame is included in the reference frame formed by the forming unit, and estimates that the single image as the target of type inference contained in the bounding frame is another image than the character image when the bounding frame is not included in the reference frame formed by the forming unit, when the estimating unit estimates that the single image is the character image, the estimating unit further estimates that the designation region is a character image region containing one or more character images when an occupied quantity of character images in the designation region is not smaller than an occupied quantity of one or more images other than the character images in the designation region, and when the estimating unit estimates that the single image is said another image than the character image, the estimating unit further estimates that the designation region is a non-character image region containing one or more images other than character images when an occupied quantity of character images in the designation region is smaller than an occupied quantity of one or more images other than the character images in the designation region.