Decision Making Scenario

To identify or reject the individuals concerning the matched SRs in the proposed hierarchical matching structure, we propose a decision making scenario based on the matching results of SRs. This decision making scenario is defined so that the identification or rejection of an individual with the least number of SR matching process is carried out. For this purpose, according to matched SRs of the query in each irritation, decision making scenario determines that the SR matching process should be continued or stopped.

Assume and be the first two matched SRs (SR a and SR b) that belong to the same individual in the database and , be the centroids of these two SRs. Moreover, and be their corresponding matched SRs in the query image with the centroids of and . Euclidean distance between the centroids of each pair of these matched SRs in the query and enrolled image in the database is computed as,

(14)

Since the centroid of SR is the most robust point of a SR against noise and movement factors in whole of a retinal image (because the centroid is obtained by averaging all points of a region and not only border points), we use the distance between the centroids of two SRs in the query and enrolled images in the database to decide in the decision making scenario as in the following,

(15)

where is a predefined threshold. In Eq. (15), if individual is identified, the SR matching process will be stopped. Otherwise, the SR matching process continue until our decision making scenario identify an individual image in the database or all greatest extracted SR from the query image are investigated and finally the query image is rejected if none of the matched SR pairs does not satisfy the condition in our decision making scenario(Eq. (15)). Fig. 8 shows a query image that has been identified by an enrolled image in the database. In the images of Fig. (8-a) and Fig. (8-b), two pairs of the matched SRs in the enrolled image in the database and query image are shown with their centroids. Notice that the distance between two centroids described in Eq. (14) is completely different from centroid distance explained in section (2.2.1.4) and used in corner matching (section (2.3.2))

(a) (b)

Fig. 8: Decision making scenario. (a) Two matched SRs in an enrolled image of the database with their centroids, (b) Two matched SRs in the query image with their centroids.

Date: 2016-04-22; view: 747