Feature file standard_v0.1

Overview

Communication between keypoint generator and matcher softwares is performed through ASCII files. The most simple format is considered in the feature-suite. The following sections describe the file standards expected by the softwares provided by feature-suite.

Standards for keypoints files

A keypoints file starts with the number of keypoints carried by the file. Then, each file line describe a keypoint. Keypoints have a structure inherited from OpenCV keypoint structure. The x and y coordinates of the keypoint are the first values on the line. The size, angle, response and octave are the four next values. For more information, please see OpenCV documentation.

A typical keypoints file starts as follow :

979
673.999 1398.92 2.08473 23.5999 0.0788755 10813951
483.803 1418.49 2.08771 289.006 0.0507617 10879487
483.803 1418.49 2.08771 53.4739 0.0507617 10879487
1619.65 1422.05 1.88516 200.793 0.0546359 3539455
...

The number of keypoints is not limited by the file format.

Standards for matches files

Matches files start with the number of matches carried by the file. Then, each line of the file stores one matches descriptor. The first value is the index of the keypoint in the keypoints file of the first image.The second value gives the same information for the keypoint of the second image. The x and y coordinates of the keypoints in the first and second image are the next four values.

1588
478 644 1143.16 434.755 1179.46 400.729
511 665 1185.43 446.775 1221.94 408.879
516 661 1232.54 448.541 1269 408.421
620 786 1135.02 507.123 1171.04 474.402
...

As for keypoints files, the number of matches is not limited.