Euro money bill recognition

The project shows detection and recognition of euro money bill from input image (webcam). For each existing euro money bill is chosen template that contains number value of bill and also its structure. For matching templates with input images is used Flann Based matcher of local descriptors extracted by SURF algorithm.

Functions used: medianBlur, FlannBasedmatcher, SerfFeatureDetector, SurfDescriptorExtractor, findHomography

Process

1. Preprocessing – Conversion to grayscale + median filter

   cvtColor(input_image_color, input_image, CV_RGB2GRAY);
   medianBlur(input_image, input_image, 3);
   

2. Compute local descriptors

   SurfFeatureDetector detector( minHessian );
   vector<KeyPoint> template_keypoints;
   detector.detect( money_template, template_keypoints );
   SurfDescriptorExtractor extractor;
   extractor.compute( money_template, template_keypoints, template_image );
   detector.detect( input_image, input_keypoints );
   extractor.compute( input_image, input_keypoints, destination_image );
   

3. Matching local descriptors

   FlannBasedMatcher matcher;
   matcher.knnMatch(template_image, destination_image, matches, 2);
   

4. Finding homography and drawing output

   Mat H = findHomography( template_object_points, input_object_points, CV_RANSAC );
   perspectiveTransform( template_corners, input_corners, H);
   drawLinesToOutput(input_corners, img_matches, money_template.cols);
   

Sample