Patent ID: 8687886

Claim:
An image-based document indexing method implemented in a data processing system which includes a processor and a memory or storage device, the method comprising: (a) the data processing system obtaining a document image including at least one page; (b) the data processing system segmenting the page of the document image into one or more text regions; (c) the data processing system analyzing the page of the document image to generate page-level index information; (d) for each text region in the page: (d1) the data processing system segmenting the region into a plurality of units each having a unit length and/or a unit density; and (d2) the data processing system generating a unit length histogram and/or a unit density histogram, wherein the unit length histogram has a plurality of bins and represents a relationship between the unit length and a frequency of occurrence of the units within the region, the unit density histogram has a plurality of bins and represents a relationship between the unit density and a frequency of occurrence of the units within the region, and wherein each unit of the region belongs to a bin of the unit length histogram or the unit density histogram; wherein the unit length histogram or unit density histogram forms region-level index information for the region; (e) for each text region, and for each of a number of designated bins of the unit length histogram or unit density histogram, including a most frequent bin and zero or more bins around the most frequent bin: (e1) the data processing system characterizing each unit belonging to the bin into a unit type and obtain a number of unit types in the bin; and (e2) for each of a number of designated unit types, the data processing system obtaining a number of units belonging to the unit type, locations of such units, and a unit feature vector or unit image patch of the unit type; wherein the identity of the designated bins, the numbers of unit types in each designated bin, the number of units belonging to each designated unit type and the locations of such units, and the unit feature vector or unit image patch of each designated unit type collectively form unit-level index information for the region; and wherein the page-level index information, the region-level index information and the unit-level index information collectively form the document index information of the document image.