Estimation of local defocus distance and geometric distortion based on scanned image features

摘要

A method of estimating local defocus distance from a conventionally scanned image is provided. More particularly, the method of estimating defocus distance in a scanned image of a non-planar original object, such as an open book, includes scanning at least a portion of the book in order to produce scanned image data. An image feature obtainable from the scanned image data and a quantitative metric corresponding to the image feature are selected. Image feature data is extracted from the scanned image data and compared to a predetermined calibration relationship between the selected image feature and defocus distance in order to calculate a plurality of defocus distances, which are organized into a defocus distance map. The defocus distance map may be used in the subsequent correction of geometric distortions, blurring defects, and illumination variations adjacent the binding of an open book.