Spherical Image Compression via Latitude-Dependent Coefficient Discard
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing digital image compression techniques, such as JPEG, face challenges in achieving efficient compression for spherical images without compromising picture quality, particularly when projecting rectangular images onto a sphere, as they fail to account for latitude-based distortion and unnecessary detail retention.
Innovation Solution
A non-uniform compression method that identifies and discards horizontal frequency coefficients based on latitude information, increasing the number of discarded coefficients as the latitude approaches the pole, thereby reducing the image file size without impacting picture quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of substance
If uniform compression is applied across the entire spherical image, then the compression ratio is improved, but the picture quality deteriorates due to loss of important details in equatorial regions
Solution Approach 1:
The patent applies different compression strategies to different latitude regions of the spherical image. Equatorial regions (lower latitudes) use standard JPEG compression to preserve important visual details, while polar regions (higher latitudes) use enhanced compression that discards more coefficients. This local differentiation resolves the contradiction by maintaining picture quality where it matters most while achieving better overall compression ratio through aggressive compression in less visually critical polar areas.
2Loss of substance
If aggressive quantization is used to reduce storage space, then the compression ratio is improved, but the picture quality deteriorates due to loss of image details
Solution Approach 1:
The patent implements latitude-dependent quantization where the aggressiveness of compression varies by region. In equatorial regions, milder quantization preserves important image details, while in polar regions, more aggressive quantization discards coefficients that contribute less to perceived image quality. This resolves the contradiction by achieving greater overall storage savings without sacrificing picture quality in visually critical areas.
Solution Approach 2:
The patent exploits the natural distortion and pixel squeezing that occurs at polar regions during spherical projection. Instead of treating this as a harmful distortion that must be preserved, it converts this characteristic into a benefit by applying enhanced compression to these regions, discarding coefficients that would otherwise be wasted storage space but contribute minimally to the final displayed image quality.
3Manufacturing precision
If all frequency coefficients are retained to maintain picture quality, then the picture quality is improved, but the storage space requirement increases
Solution Approach 1:
The patent selectively retains frequency coefficients based on latitude. In equatorial regions, more coefficients are retained to preserve picture quality, while in polar regions, fewer coefficients are retained as the squeezed pixels contribute less to perceived quality. This resolves the contradiction by optimizing the balance between storage space and picture quality in a region-specific manner.
Data Source
AI summary
Disclosed herein is a projection-aware compression, which may be used on image data such as, for example, spherical image data. The compression may be considered to be non-uniform in a sense that the compression need not be uniformly applied, but may be applied to image data as a function of latitude information associated with the image data.