Document Edge Detection via Luminance Adjustment
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Solution Overview
Problem
Existing multi-cropping processing methods for scanning documents on a glass platen face challenges in detecting document edges due to low luminance contrast between white documents and the white glass platen background, leading to issues like user discomfort and decreased image quality.
Innovation Solution
An image processing apparatus that adjusts luminance to preserve high signal values, detects document positions, and crops document images based on detected coordinates, using luminance adjustment units to enhance edge detection and image quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the glass platen cover is opened to output black background, then document edge detection is facilitated, but user comfort deteriorates due to illumination light hitting eyes
Solution Approach 1:
The patent changes the luminance parameter of the background region through image processing. By detecting the glass platen cover region and adjusting its luminance to be lower than the document region, the system creates sufficient luminance difference for accurate edge detection without requiring the cover to be physically opened, thus avoiding user discomfort from direct illumination light.
2Measurement precision
If the glass platen cover is opened for scanning, then document edge detection is improved, but document pressing capability is lost causing curled documents to raise
Solution Approach 1:
The patent maintains the glass platen cover in the closed state during scanning to ensure proper document pressing. Through image processing, the system adjusts the luminance parameter of the background region to create sufficient contrast with the document region, enabling accurate edge detection while maintaining document flatness and image quality consistency.
3Measurement precision
If luminance adjustment is performed to enhance document-background contrast, then edge detection accuracy is improved, but processing complexity increases
Solution Approach 1:
The patent applies luminance adjustment locally only to the glass platen cover region rather than the entire image. By detecting the cover region boundaries and adjusting luminance specifically in this area, the system achieves the required contrast enhancement with minimal processing complexity, avoiding the need for complex global image processing algorithms.
4Measurement precision
If black sheet is placed on documents to facilitate edge detection, then document edge detection is improved, but user operation burden increases
Solution Approach 1:
The patent enables the system to automatically differentiate between document regions and glass platen cover regions through luminance analysis and region detection algorithms. The system performs self-service by automatically adjusting the luminance of the background region without requiring user intervention to place black sheets or other physical aids, thereby maintaining ease of operation while achieving accurate edge detection.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Facilitates accurate detection and cropping of document edges, improving image quality and user experience by differentiating document and background luminance, thus overcoming previous limitations.
Implementation Method 1
an image acquired by reading the document placed on a glass platen
Implementation Method 2
reading a document by a scanner
Data Source
AI summary
An image processing apparatus generates a first image by adjusting luminance so as to preserve a signal value on a high-luminance side among signal values acquired by reading a document by a scanner, and detects a position of a region corresponding to the document in the generated first image. The image processing apparatus further generates a second image by performing adjustment so as to increase luminance of a pixel contained in the first image, and crops a document image from the generated second image based on the detected position of the region corresponding to the document.