Virtual lens simulation for video and photo cropping
In a video capture system, a virtual lens is simulated when applying a crop or zoom effect to an input video. An input video frame is received from the input video that has a first field of view and an input lens distortion caused by a lens used to capture the input video frame. A selection of a sub-frame representing a portion of the input video frame is obtained that has a second field of view smaller than the first field of view. The sub-frame is processed to remap the input lens distortion to a desired lens distortion in the sub-frame. The processed sub-frame is the outputted.
1. A system that simulates image distortion of a virtual lens in an image, the system comprising:
one or more processors; and
a non-transitory computer-readable storage medium storing instructions that when executed cause the one or more processors to perform steps including:
accessing an input image, the input image including a first field of view of a scene, the input image depicting the scene with an input lens distortion centered in the first field of view;
selecting a sub-frame representing a portion of the input image, the sub-frame including a second field of view of the scene smaller than the first field of view, the sub-frame including a lens distortion effect as a function of the input lens distortion present in the input image, a position of an area of the input image included within the second field of view, and a size of the area of the input image included within the second field of view; and
generating an output image based on a desired lens distortion and the lens distortion effect in the sub-frame, the desired lens distortion and the input lens distortion exhibiting consistent lens characteristics, wherein the output image includes the sub-frame remapped from the input lens distortion centered in the first field of view to the desired lens distortion centered in the second field of view to transform the lens distortion effect present in the sub-frame to the desired lens distortion such that a portion of the scene depicted in the sub-frame appears to have been captured using the second field of view.
2. The system of claim 1 , wherein image stabilization is applied to the input image.
3. The system of claim 1 , wherein the sub-frame is selected based on metadata associated with the input image.
4. The system of claim 3 , wherein the metadata indicates motion of a camera that captured the input image.
5. The system of claim 3 , wherein the metadata indicates orientation of a camera that captured the input image.
6. The system of claim 5 , wherein the metadata is generated by a sensor of the camera.
7. The system of claim 6 , wherein the sensor includes an orientation sensor, an accelerometer, a gyroscope, or a magnetometer.
8. The system of claim 1 , wherein generating the output image comprises:
applying an inverse input function to the sub-frame to remove the input lens distortion effect present in the sub-frame; and
applying a desired lens distortion function to apply the desired lens distortion to the subframe.
9. The system of claim 8 , wherein:
the application of the inverse input function to the sub-frame transforms the sub-frame to a rectilinear image in which straight lines in the portion of the scene depicted in the sub-frame appear straight; and
the desired lens distortion function is centered at a center of the sub-frame.
10. The system of claim 1 , wherein generating the output image comprises:
applying a direct function to remap the sub-frame without an intermediate step of removing the input lens distortion effect present in the sub-frame.
11. A method for simulating image distortion of a virtual lens in an image, the method comprising:
accessing an input image, the input image including a first field of view of a scene, the input image depicting the scene with an input lens distortion centered in the first field of view;
selecting a sub-frame representing a portion of the input image, the sub-frame including a second field of view of the scene smaller than the first field of view, the sub-frame including a lens distortion effect as a function of the input lens distortion present in the input image, a position of an area of the input image included within the second field of view, and a size of the area of the input image included within the second field of view; and
generating an output image based on a desired lens distortion and the lens distortion effect in the sub-frame, the desired lens distortion and the input lens distortion exhibiting consistent lens characteristics, wherein the output image includes the sub-frame remapped from the input lens distortion centered in the first field of view to the desired lens distortion centered in the second field of view to transform the lens distortion effect present in the sub-frame to the desired lens distortion such that a portion of the scene depicted in the sub-frame appears to have been captured using the second field of view.
12. The method of claim 11 , wherein image stabilization is applied to the input image.
13. The method of claim 11 , wherein the sub-frame is selected based on metadata associated with the input image.
14. The method of claim 13 , wherein the metadata indicates motion of a camera that captured the input image.
15. The method of claim 13 , wherein the metadata indicates orientation of a camera that captured the input image.
16. The method of claim 15 , wherein the metadata is generated by a sensor of the camera.
17. The method of claim 16 , wherein the sensor includes an orientation sensor, an accelerometer, a gyroscope, or a magnetometer.
18. The method of claim 11 , wherein generating the output image comprises:
applying an inverse input function to the sub-frame to remove the input lens distortion effect present in the sub-frame; and
applying a desired lens distortion function to apply the desired lens distortion to the subframe.
19. The method of claim 18 , wherein:
the application of the inverse input function to the sub-frame transforms the sub-frame to a rectilinear image in which straight lines in the portion of the scene depicted in the sub-frame appear straight; and
the desired lens distortion function is centered at a center of the sub-frame.
20. The method of claim 11 , wherein generating the output image comprises:
applying a direct function to remap the sub-frame without an intermediate step of removing the input lens distortion effect present in the sub-frame.