Image reading apparatus, image reading method, and recording medium therefor, that improve quality of image of document obtained by portable image device

1. An image reading apparatus for reading a document image represented on a document set on a planar background surface, the image reading apparatus comprising:

storage storing a document-image-obtaining application program;

an imaging unit configured by the document-image-obtaining application program to generate from the document image a plurality of data images of varying shadow location, by imaging the document image multiple times from mutually differing angles;

an image forming unit having processing circuitry configured by the document-image-obtaining application program to function as

an image data analysis unit for performing a matching process on the plurality of data images by matching the plurality of data images, on a per-region basis in each of the plurality of images of the document represented by the plurality of data images of varying shadow location to obtain per-region brightnesses for the plurality of data images, and for each matching region comparing the obtained brightnesses to select from among the plurality of data images each data image whose per-region brightness is comparatively brighter and is within a predetermined range defining a shadowless state; and

an image compositing unit for using the data images selected on the per-region basis as comparatively brighter and within the predetermined range defining the shadowless state, to generate a composite data image, and for prompting the imaging unit to reimage the document image when for any matching region, none among the plurality of data images has a brightness that is within the predetermined range defining the shadowless state.

2. The image reading apparatus according to claim 1 , wherein the image data analysis unit extracts as the document image, from among the images represented by the plurality of data images, an image in a region having a contour with a peripheral area outside a central region located in a center portion of the image.

3. The image reading apparatus according to claim 1 , wherein the image data analysis unit obtains from the planar background surface a platen image as an image of a platen before the document is arranged and extracts the document image by removing a region similar to the platen image.

4. The image reading apparatus according to claim 1 , wherein the image compositing unit generates a histogram of the composite data image and executes a level correction using the histogram.

5. The image reading apparatus according to claim 1 , wherein the image data analysis unit extracts a feature point from respective images represented by the plurality of data images, and performs matching on the plurality of data images by deforming the plurality of data images such that the extracted feature points correspond.

6. An image forming apparatus comprising:

the image reading apparatus according to claim 1 ; and

an image forming unit that forms an image of the composite data image generated by the image reading apparatus on a print medium.

7. An image reading method for reading a document image represented on a document set on a planar background surface, the image reading method comprising:

generating from the document image a plurality of data images of varying shadow location, by imaging the document image multiple times from mutually differing angles;

performing a matching process on the plurality of data images by matching the plurality of data images, on a per-region basis in each of the plurality of images of the document represented by the plurality of data images of varying shadow location to obtain per-region brightnesses for the plurality of data images, and for each matching region comparing the obtained brightnesses to select from among the plurality of data images each data image whose per-region brightness is comparatively brighter and is within a predetermined range defining a shadowless state; and

using the data images selected on the per-region basis as comparatively brighter and within the predetermined range defining the shadowless state, to generate a composite data image, and reimaging the document image when for any matching region, none among the plurality of data images has a brightness that is within the predetermined range defining the shadowless state.

8. A non-transitory computer-readable recording medium that stores an image reading program for controlling an image reading apparatus for reading a document image represented on a document set on a planar background surface, the image reading program causing the image reading apparatus to function as:

an imaging unit for generating from the document image a plurality of data images of varying shadow location, by imaging the document image multiple times from mutually differing angles;

an image data analysis unit for performing a matching process on the plurality of data images by matching the plurality of data images, on a per-region basis in each of the plurality of images of the document represented by the plurality of data images of varying shadow location to obtain per-region brightnesses for the plurality of data images, and for each matching region comparing the obtained brightnesses to select from among the plurality of data images each data image whose per-region brightness is comparatively brighter and is within a predetermined range defining a shadowless state; and

an image compositing unit for using the data images selected on the per-region basis as comparatively brighter and within the predetermined range defining the shadowless state, to generate a composite data image, and for prompting the imaging unit to reimage the document image when for any matching region, none among the plurality of data images has a brightness that is within the predetermined range defining the shadowless state.