Fisheye Image Stitching via 90-Degree Rotation to Reduce Seam Discontinuities
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Solution Overview
Problem
Conventional methods for processing fisheye images result in noticeable discontinuities at the seam of panoramic images, particularly at high altitudes, leading to poor image quality due to significant distortion during equirectangular projection and stitching.
Innovation Solution
The method involves performing an equirectangular projection on fisheye images, swapping and rotating them by 90 degrees in a spherical coordinate system, stitching them, and then reversing the rotation to create a panoramic image, which alleviates seam discontinuities and enhances image quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If equirectangular projection and stitching are performed on fisheye images using conventional methods, then a panoramic image is generated, but noticeable discontinuities appear at the seam particularly at high altitudes
Solution Approach 1:
The patent applies preliminary action by rotating the equirectangular images by 90 degrees before stitching, so that the stitching operation occurs along the equator rather than at high altitudes. This pre-rotation prepares the images in an optimal orientation that prevents seam discontinuities from appearing in the final panoramic view, thereby resolving the technical contradiction between seam continuity and processing complexity.
Solution Approach 2:
The patent employs inversion by reversing the conventional stitching approach. Instead of stitching images in their standard orientation and accepting high-altitude seams, it inverts the process by rotating images 90 degrees, stitching along the equator, and then rotating back. This inverted approach transforms the harmful high-altitude seam discontinuities into negligible equatorial seams that are not visible in the final panoramic image.
2Device complexity
If fisheye images are directly stitched after equirectangular projection, then processing is simplified, but significant distortion occurs particularly at high altitudes
Solution Approach 1:
The patent applies preliminary action by performing a 90-degree rotation of equirectangular images before stitching. This pre-rotation reorients the images so that the stitching operation occurs along the equator where distortion is minimal, rather than at high altitudes where distortion is severe. This preliminary step prevents excessive distortion while maintaining processing simplicity.
Solution Approach 2:
The patent employs parameter changes by altering the orientation parameter of equirectangular images through 90-degree rotation. This parameter change transforms the images from a state where high-altitude stitching would cause severe distortion to a state where equatorial stitching minimizes distortion. The rotation modifies the spatial parameters of the images to achieve optimal stitching conditions.
3Productivity
If conventional stitching is performed on equirectangular images, then processing time is reduced, but seam discontinuities severely affect image quality
Solution Approach 1:
The patent applies preliminary action by rotating equirectangular images by 90 degrees before stitching. This pre-rotation prepares the images in an optimal orientation that enables fast equatorial stitching while preventing seam discontinuities from appearing in the final panoramic image. The preliminary rotation step is computationally efficient and maintains high processing speed while dramatically improving image quality.
Solution Approach 2:
The patent employs inversion by reversing the conventional stitching orientation. Instead of stitching in the standard orientation where seams appear at high altitudes and degrade image quality, it inverts the approach by rotating images 90 degrees, stitching along the equator, and rotating back. This inverted method maintains processing speed while eliminating visible seam discontinuities, thereby resolving the contradiction between productivity and image quality.
Data Source
AI summary
An image processing method includes: performing an equirectangular projection on a first fisheye image and a second fisheye image to obtain a first equirectangular image and a second equirectangular image; swapping positions of a left-half image of the second equirectangular image and a right-half image of the second equirectangular image to obtain a third equirectangular image; rotating the first equirectangular image and the third equirectangular image by 90 degrees in a spherical coordinate system to obtain a first rotated image and a second rotated image; stitching the first rotated image and the second rotated image to obtain a stitched image; and rotating the stitched image by −90 degrees in the spherical coordinate system to obtain a panoramic image.