The problem of the recognition of document image can be complex because it requires to be robust in translation, rotation and zoom. It may also happen that the documents are degraded (noise, spots, cuts, etc.).
Techniques based on using interest points such as SIFT and SURF are commonly used in natural images (pictures). I worked on an extension of this method to quickly recognize patterns document given by a user, such as an identity card, a passport, train ticket, etc..
The method is simple and extensible to many other image document, it is divided into four main steps:
- Extraction of interest points. (SURF)
- Description of points. (SURF)
- Matching the current image points with those of the query image. (FLANN)
- Estimation of a 4-parameter transformation. (RANSAC)
Technological choices in brackets will be changed in the future by new more efficient algorithms and more suitable to the context.
The details of the technique can be found in the publication in 2012 CIFED: Recognition and Extraction of identity documents (in French).