Method, program and apparatus for storing document and/or image using invariant values calculated from feature points and method, program and apparatus for retrieving document based on stored document and/or image

A document and/or image storage method, which causes a computer to execute the steps of:

• inputting a document and/or image;
• assigning an ID to the input document and/or image;
• extracting feature points defining an image arrangement from the input document and/or image;
• and performing a predetermined process on each of the extracted feature points;
• the predetermined process comprising the steps of:
• (1) selecting n feature points which are nearest to a feature point p of interest;
• and
• (2) performing a predetermined process on each of all possible sets of m feature points, m<n, selected from the selected n feature points;
• the predetermined process in the performing step comprising the steps of:
• (a) determining features, for each of which includes a set of invariant values, for all possible sets of d points, wherein d is a number not greater than a predetermined number m, selected from an m-point set of interest;
• (b) determining an index of a hash table based on the determined features through a predetermined computation;
• and
• (c) storing the features in relation to a point ID and a document ID in the hash table, the features being determined in the features determining step using the determined hash index, the point ID being assigned to the feature point p and the document ID being assigned to the document and/or image from which the feature point p is extracted.

A non transitory computer readable medium storing a document and/or image storage program, which causes a computer to execute the steps of:

• inputting a document and/or image;
• assigning an ID to the input document and/or image;
• extracting feature points defining an image arrangement from the input document and/or image;
• and
• performing a predetermined process on each of the extracted feature points;
• the predetermined process including the steps of:
• (1) selecting n feature points which are nearest to a feature point p of interest;
• and
• (2) performing a predetermined process on each of all possible sets of m feature points, m<n, selected from the selected n feature points;
• the predetermined process in the performing step including the steps of:
• (a) determining features for each of which includes a set of invariant values for all possible sets of d points wherein d is a number not greater than a predetermined number m, selected from an m-point set of interest;
• (b) determining an index of a hash table based on the determined features through a predetermined computation;
• and
• (c) storing the features in relation to a point ID and a document ID in the hash table, the features being determined in the features determining step using the determined hash index, the point ID being assigned to the feature point p and the document ID being assigned to the document and/or image from which the feature point p is extracted.

A document and/or image storage apparatus comprising:

• a processor;
• an input section which inputs a document and/or image;
• a feature point extracting section which extracts feature points defining an image arrangement from the input document and/or image;
• a feature point selecting section which selects n feature points nearest to an extracted feature point p of interest;
• and
• a feature storing section which performs a predetermined process on each of all possible sets of m feature points, m<n, selected from the selected n feature points;
• the predetermined process including the steps of:
• (a) determining features for each of which includes a set of invariant values for all possible sets of d points, wherein d is a number not greater than a predetermined number m, selected from an m-point set of interest;
• (b) determining an index of a hash table based on the determined features through a predetermined computation;
• and
• (c) storing the features in relation to a point ID and a document ID in the hash table, the features being determined in the features determining step using the determined hash index, the point ID being assigned to the feature point p and the document ID being assigned to the document and/or image from which the feature point p is extracted.

A document and/or image retrieval apparatus comprising:

• a processor;
• a reading section which reads a captured image;
• a feature point extracting section which extracts feature points defining an image arrangement from the read image;
• a feature point selecting section which selects n feature points nearest to an extracted feature point p of interest;
• and
• a voting section which performs a predetermined process on each of all possible sets of m feature points, m<n, selected from the selected n feature points;
• the predetermined process including the steps of:
• (a) determining features for all possible sets of d points, wherein d is a number not greater than a predetermined number m, selected from an m-point set of interest;
• (b) determining an index of a hash table based on the determined features through a predetermined computation;
• and
• (c) acquiring features of a preliminarily input document and/or image from the hash table based on the determined hash index, comparing the features determined in the features determining step with the acquired features, and voting for a document ID having matching features;
• and a document ID specifying section which specifies a document ID of a document/image which matches the captured image based on a voting result determined by votes corresponding to the respective feature points.