Image alignment using a virtual gyroscope model

A non-transitory computer-readable apparatus comprising a computer program configured to align a target image to a reference image in the presence of lens distortion, the computer program comprising instructions that, when executed by a processor apparatus, cause the processor apparatus to:

• receive the target image and the reference image;
• detect a first plurality of visual features appearing in the target image at first image feature coordinates in a two-dimensional image space, and a corresponding second plurality of visual features appearing in the reference image at second image feature coordinates in the two-dimensional image space;
• transform the first image feature coordinates and the second image feature coordinates from the two-dimensional image space to a three-dimensional spherical space to generate respective first spherical feature coordinates and second spherical feature coordinates;
• apply a rotation to the target image in the three-dimensional spherical space to generate a rotated target image via at least:
• determination of at least a subset of the first spherical feature coordinates and a corresponding subset of the second spherical feature coordinates as background features in the target image and the reference image, respectively;
• determination of feature tracks representing a distance along a spherical arc and direction from the first spherical feature coordinates to a corresponding one of the second spherical feature coordinates;
• cluster the feature tracks by length to determine a plurality of feature track clusters;
• and
• determine, from the plurality of feature track clusters, a background cluster of feature tracks corresponding to the background features;
• and
• inverse transform the rotated target image to the two-dimensional image space.

A video server comprising:

• one or more processors;
• and
• a non-transitory computer-readable apparatus comprising a computer program configured to align a target image to a reference image in the presence of lens distortion, the computer program comprising instructions that, when executed by the one or more processors, causes the one or more processors to:
• receive the target image and the reference image;
• detect a first plurality of visual features appearing in the target image at first image feature coordinates in a two-dimensional image space, and a corresponding second plurality of visual features appearing in the reference image at second image feature coordinates in the two-dimensional image space;
• transform the first image feature coordinates and the second image feature coordinates from the two-dimensional image space to a three-dimensional spherical space to generate respective first spherical feature coordinates and second spherical feature coordinates;
• apply a rotation to the target image in the three-dimensional spherical space to generate a rotated target image via at least:
• determination of at least a subset of the first spherical feature coordinates and a corresponding subset of the second spherical feature coordinates as background features in the target image and the reference image, respectively;
• determination of feature tracks representing a distance along a spherical arc and direction from the first spherical feature coordinates to a corresponding one of the second spherical feature coordinates;
• cluster the feature tracks by length to determine a plurality of feature track clusters;
• and
• determine, from the plurality of feature track clusters, of a background cluster of feature tracks corresponding to the background features;
• and
• inverse transform the rotated target image to the two-dimensional image space.