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# Homography Scale and Rotation

For evaluation of the FeEval challenge scale and rotation, affine 2d homography has to be known.

To evaluate to robustness to scale and rotation we increasingly shrink the videos to a final size of 30% of the original size and rotate them by 10% for every level.

The homography matrices are estimated as follows:

 1 0 0 0 1 0 0 0 1

 1 0 x 0 1 y 0 0 1

 cos(angle) sin(angle) 0 -sin(angle) cos(angle) 0 0 0 1

 scaling factor 0 0 0 scaling factor 0 0 0 1

The final homography matrix is then computed by

H = inv(H_trans) * H_scale * H_rot * H_trans

H_trans is the translation to the frame center.

Example for the TV show videos:

`H1 = estimate_homography(312, 163, -10, 0.9)H2 = estimate_homography(312, 163, -20, 0.8)H3 = estimate_homography(312, 163, -30, 0.7)H4 = estimate_homography(312, 163, -40, 0.6)H5 = estimate_homography(312, 163, -50, 0.5)H6 = estimate_homography(312, 163, -60, 0.4)H7 = estimate_homography(312, 163, -70, 0.3)`