Optimization and use of codebooks for document analysis

A system, comprising:

• a memory,
• a processor coupled to the memory, the processor configured to:
• receive a first set of document images;
• extract a plurality of keypoint regions from each document image of the first set of document images;
• calculate local descriptors for each keypoint region of the extracted keypoint regions;
• cluster the local descriptors such that each center of a cluster of local descriptors corresponds to a respective visual word;
• generate a codebook containing a set of visual words;
• and
• optimize the codebook by maximizing mutual information (MI) between a target field of a second set of document images and at least one visual word of the set of visual words;
• and
• detect, using the codebook, one or more fields in a document image.

A non-transitory computer-readable storage medium comprising instructions that, when executed by a processing device, cause the processing device to:

• receive, a first set of document images;
• extract a plurality of keypoint regions from each document image of the first set of document images;
• calculate local descriptors for each keypoint region of the extracted keypoint regions;
• cluster the local descriptors such that each center of a cluster of local descriptors corresponds to a respective visual word;
• generate a codebook containing a set of visual words;
• optimize the codebook by maximizing mutual information (MI) between a target field of a second set of document images and at least one visual word of the set of visual words;
• and
• detect, using the codebook, one or more fields in a document image.