Image processing apparatus, image reading device, image forming apparatus, and image processing method

An image processing apparatus comprising:

• a first edge point group detection unit configured to detect a first edge point group comprising a set of edge points between a document background area and a document area in a read image of a document, the read image being output from an imaging unit;
• an edge point feature amount calculation unit configured to calculate feature amounts from a plurality of edge points in the first edge point group and compose an edge point feature amount group;
• a distribution calculation unit configured to calculate a distribution of the feature amounts of the plurality of edge points from the edge point feature amount group and calculate a feature amount corresponding to a maximum distribution;
• an edge point selection unit configured to select edge points corresponding to the maximum distribution from the first edge point group and select a second edge point group using a range of the feature amount corresponding to the maximum distribution calculated by the distribution calculation unit;
• and
• an edge straight line calculation unit configured to calculate an edge straight line approximating the second edge point group.