Equatorial Stitching for Spherical Image Distortion Reduction
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Solution Overview
Problem
Conventional image stitching algorithms for spherical images often result in undesirable artifacts around stitch lines due to distortion introduced during the projection of images from a spherical to a rectangular format, particularly exacerbated near the poles in equirectangular projections.
Innovation Solution
The equatorial stitching technique remaps the spherical images so that the stitch line is placed along the equator, where distortion is minimal, allowing for a single stitch line with reduced distortion and enabling accurate feature matching and smooth transitions across all axes, even with non-sphere-aware stitching software.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional stitching algorithms are used to combine multiple spherical images, then the stitching process can be completed, but undesirable artifacts appear around stitch lines due to distortion introduced during projection to rectangular format
Solution Approach 1:
The patent applies preliminary action by performing the remapping of spherical images to reposition stitch lines along the equator before the actual stitching process. This preliminary repositioning ensures that stitching occurs in the region of minimal distortion, preventing artifacts from appearing in the final stitched image while maintaining efficient processing.
Solution Approach 2:
The patent changes the spatial parameter of the stitch line location by remapping the spherical coordinate system. Instead of stitching along arbitrary or conventional lines, the system transforms the image data so that stitch lines align with the equator where distortion parameters are minimized, thereby resolving the contradiction between productivity and precision.
2Adaptability or versatility
If equirectangular projection is used to convert spherical images to rectangular format, then the images can be processed with standard software, but distortion is exacerbated near the poles
Solution Approach 1:
The patent applies local quality by identifying that different regions of the spherical image have different distortion characteristics. The equatorial region has minimal distortion while polar regions have maximal distortion. By remapping to perform stitching along the equator, the system utilizes the high-quality low-distortion region for the critical stitching operation, while accepting that polar regions will have distortion but are not used for stitching.
3Area of stationary object
If multiple stitch lines are created to capture full spherical view, then complete coverage is achieved, but more artifacts and complexity are introduced
Solution Approach 1:
The patent applies merging by combining multiple hemispherical or spherical image captures into a unified coordinate system where all stitching operations occur along the equator. This consolidation reduces the number of separate stitch line operations needed, as the equatorial stitching approach allows for more efficient tiling and assembly of multiple spherical views with minimal artifacts and reduced overall system complexity.
Data Source
AI summary
Hyper-hemispherical images may be combined to generate a rectangular projection of a spherical image having an equatorial stitch line along of a line of lowest distortion in the two images. First and second circular images are received representing respective hyper-hemispherical fields of view. A video processing device may project each circular image to a respective rectangular image by mapping an outer edge of the circular image to a first edge of the rectangular image and mapping a center point of the circular image to a second edge of the first rectangular image. The rectangular images may be stitched together along the edges corresponding to the outer edge of the original circular image.