Conversion between aspect ratios in camera
A camera system captures an image in a source aspect ratio and applies a transformation to the input image to scale and warp the input image to generate an output image having a target aspect ratio different than the source aspect ratio. The output image has the same field of view as the input image, maintains image resolution, and limits distortion to levels that do not substantially affect the viewing experience. In one embodiment, the output image is non-linearly warped relative to the input image such that a distortion in the output image relative to the input image is greater in a corner region of the output image than a center region of the output image.
1. An image capture apparatus, comprising:
an image sensor configured to capture an input image having a source aspect ratio, the input image including pixels located at input positions;
a display coupled to one or more physical processors; and
the one or more physical processors configured to:
obtain the input image;
generate an output image by applying a transformation to the input image that distorts the input image while preserving entire field of view of the input image within the output image, the output image having a target aspect ratio different than the source aspect ratio, the output image including the pixels located at output positions; and
present the output image on the display;
wherein:
the transformation includes a linear scaling to uniformly stretch or compress the input image and a non-linear warping to non-uniformly warp the input image;
the linear scaling and the non-linear warping change the pixels from being located at the input positions in the input image to the output positions in the output image; and
the nonlinear warping includes:
a horizontal warping that changes pixel positions as a function of horizontal coordinates of the pixels; an amount of horizontal change in pixel positions characterized by a horizontal distortion offset that an individual pixel moves away from a first reference edge; and
a vertical warping that changes the pixel positions as a function of vertical coordinates of the pixels, an amount of vertical change in pixel positions characterized by a vertical distortion offset that the individual pixel moves away from a second reference edge different from the first reference edge.
2. The image capture apparatus of claim 1 , wherein the horizontal warping is tuned in combination with the vertical warping to preserve width of objects throughout a horizontal plane.
3. A system that converts between aspect ratios, the system comprising:
one or more physical processors configured to:
obtain an input image, the input image having a source aspect ratio, the input image including pixels located at input positions; and
generate an output image by applying a transformation to the input image, the output image having a target aspect ratio different than the source aspect ratio, the output image including the pixels located at output positions, wherein:
the transformation includes a linear scaling to uniformly stretch or compress the input image and a non-linear warping to non-uniformly warp the input image;
the linear scaling and the non-linear warping change the pixels from being located at the input positions in the input image to the output positions in the output image; and
the nonlinear warping includes:
a horizontal warping that changes pixel positions as a function of horizontal coordinates of the pixels, an amount of horizontal change in pixel positions characterized by a horizontal distortion offset that an individual pixel moves away from a first reference edge; and
a vertical warping that changes the pixel positions as a function of vertical coordinates of the pixels, an amount of vertical change in pixel positions characterized by a vertical distortion offset that the individual pixel moves away from a second reference edge different from the first reference edge.
4. The system of claim 3 , wherein the first reference edge includes a right edge or a left edge, and the second reference edge includes a top edge or a bottom edge.
5. The system of claim 3 , wherein the linear scaling changes the source aspect ratio to the target aspect ratio.
6. The system of claim 3 , wherein the nonlinear warping does not offset pixels along edges to prevent padding in the output image.
7. The system of claim 3 , wherein the vertical warping changes the pixel positions further as a function of the horizontal coordinates of the pixels.
8. The system of claim 3 , wherein magnitudes of distortion performed by the horizontal warping are horizontally symmetrical.
9. The system of claim 3 , wherein degradation in image quality caused by the horizontal warping is compensated for by the vertical warping.
10. The system of claim 3 , wherein the horizontal warping is tuned in combination with the vertical warping to preserve width of objects throughout a horizontal plane.
11. A method for converting between aspect ratios, the method performed by a computing system including one or more physical processors, the method comprising:
obtaining, by the computing system, an input image, the input image having a source aspect ratio, the input image including pixels located at input positions; and
generating, by the computing system, an output image by applying a transformation to the input image, the output image having a target aspect ratio different than the source aspect ratio, the output image including the pixels located at output positions, wherein:
the transformation includes a linear scaling to uniformly stretch or corn press the input image and a non-linear warping to non-uniformly warp the input image;
the linear scaling and the non-linear warping change the pixels from being located at the input positions in the input image to the output positions in the output image; and
the nonlinear warping includes:
a horizontal warping that changes pixel positions as a function of horizontal coordinates of the pixels, an amount of horizontal change in pixel positions characterized by a horizontal distortion offset that an individual pixel moves away from a first reference edge; and
a vertical warping that changes the pixel positions as a function of vertical coordinates of the pixels, an amount of vertical change in pixel positions characterized by a vertical distortion offset that the individual pixel moves away from a second reference edge different from the first reference edge.
12. The method of claim 11 , wherein the first reference edge includes a right edge or a left edge, and the second reference edge includes a top edge or a bottom edge.
13. The method of claim 11 , wherein the linear scaling changes the source aspect ratio to the target aspect ratio.
14. The method of claim 11 , wherein the nonlinear warping does not offset pixels along edges to prevent padding in the output mage.
15. The method of claim 11 , wherein the vertical warping changes the pixel positions further as a function of the horizontal coordinates of the pixels.
16. The method of claim 11 , wherein magnitudes of distortion performed by the horizontal warping are horizontally symmetrical.
17. The method of claim 11 , wherein degradation in image quality caused by the horizontal warping is compensated for by the vertical warping.
18. The method of claim 11 , wherein the horizontal warping is tuned in combination with the vertical warping to preserve width of objects throughout a horizontal plane.