Document Skew Estimation via Edge Buffer Processing
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Solution Overview
Problem
Existing image processing systems face challenges in accurately determining document skew angles, especially when documents are scanned at angles or using automatic document feeders, which affects content boundaries and requires efficient skew detection for image-processing techniques and scanning systems with limited computational resources.
Innovation Solution
A method and system for determining a rotation vector associated with a scanned document's skew angle by generating edge buffers from a normalized input image, processing them through a layer processor or constrained-histogram generator to estimate the rotation vector, involving edge detection, baseline computation, and delta determination to accurately calculate the skew angle.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional skew detection methods are used, then skew angle can be determined, but computational resources are excessively consumed
Solution Approach 1:
The patent segments the image processing task by first generating edge buffers that extract only the essential edge information from the document image, then processing these simplified edge buffers rather than the full image. This segmentation reduces computational complexity while maintaining skew detection accuracy, as the edge buffers contain only the critical structural information needed for rotation vector calculation.
Solution Approach 2:
The patent introduces edge buffers as an intermediary data structure between the original image and the skew detection algorithm. These edge buffers serve as a simplified representation that mediates between the complex original image and the computational skew detection process, reducing the data volume and computational requirements while preserving the essential geometric information needed for accurate skew angle determination.
2Measurement precision
If accurate skew angle estimation is achieved, then content boundaries can be accurately determined, but processing complexity increases
Solution Approach 1:
The patent performs preliminary edge detection and buffer generation before the actual skew detection process. By pre-processing the image to create edge buffers that highlight document boundaries and structural features, the system simplifies the subsequent skew detection task. This preliminary action ensures that the main detection algorithm works with already-processed data, reducing its complexity while maintaining accuracy in content boundary determination.
Solution Approach 2:
The patent replaces complex mechanical or iterative optimization methods with a more efficient computational approach using edge buffers and rotation vector calculation. Instead of using resource-intensive methods like exhaustive search or complex iterative optimization, the system uses the geometric properties of edge buffers to directly calculate the rotation vector, simplifying the processing algorithm while achieving accurate skew angle estimation.
Data Source
AI summary
Aspects of the present invention are related to systems and methods for determining a skew angle associated with a document image. According to a first aspect of the present invention, a rotation vector may be estimated for at least one layer in a vertical-edge buffer and a horizontal-edge buffer. According to a second aspect of the present invention, a rotation vector may be estimated directly from the vertical-edge buffer and the horizontal-edge buffer using a fixed-sized, progressively constrained histogram.