Graph-Based Text Reconstruction for Mobile Document Scanning

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Solution Overview

Problem

Character recognition on mobile devices is noisy, especially with small font sizes, and is exacerbated by limited screen area and camera field of view, leading to misread words and loss of context when trying to display and recognize text from documents.

Innovation Solution

A graph-based approach is used to reconstruct text in reading order from multiple images by generating content graphs for each image, stitching them together using graph isomorphism techniques, and selecting cluster labels based on similarity, allowing for improved recognition and noise reduction across images.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If character recognition is performed on mobile device screens, then text identification is enabled, but recognition accuracy deteriorates due to small font sizes and limited screen area

Engineering Contradiction:
Improvecharacter recognition accuracyVSAvoidscreen area
Core Design Contradiction:
Measurement precisionVSArea of stationary object

Solution Approach 1:

The patent divides the document into multiple sections by capturing several images of different portions. Each image is processed independently to identify text, and then the results are combined using graph isomorphism techniques to reconstruct the complete document in reading order, thereby overcoming the limitation of small screen area.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The patent introduces content graphs as an intermediary data structure to represent text elements and their spatial relationships. By using graph isomorphism as a mediator, the system can accurately match and combine text from multiple images, improving recognition accuracy despite small font sizes.

Inventive Principle:
Principle #24Intermediary (Mediator)

2Loss of information

If multiple images are captured to cover the entire document, then complete text coverage is achieved, but context is lost when displaying sections separately

Engineering Contradiction:
Improvecontext informationVSAvoidtext processing efficiency
Core Design Contradiction:
Loss of informationVSProductivity

Solution Approach 1:

The patent transitions from two-dimensional image data to a graph-based representation that captures spatial relationships and reading order. This dimensional transformation allows the system to maintain context information while efficiently processing multiple images by representing text elements as nodes with positional attributes.

Inventive Principle:
Principle #17Another dimension (Dimensionality change)

3Measurement precision

If graph isomorphism techniques are used to stitch content graphs, then text reconstruction accuracy is improved, but computational complexity increases

Engineering Contradiction:
Improvetext reconstruction accuracyVSAvoidcomputational complexity
Core Design Contradiction:
Measurement precisionVSDevice complexity

Solution Approach 1:

The patent applies graph isomorphism techniques locally to match specific content nodes between images based on their spatial relationships and text content. Rather than performing global graph matching, the system compares local regions and their corresponding graphs, reducing computational complexity while maintaining reconstruction accuracy.

Inventive Principle:
Principle #3Local quality

Data Source

PatentUS9424668B1Session-based character recognition for document reconstruction
Publication Date: 2016.08.23 GOOGLE LLC
  • US9424668B1 patent drawing
  • US9424668B1 patent drawing
  • US9424668B1 patent drawing

AI summary

Systems and methods are provided for sharing a screen from a mobile device. For example, a method includes receiving an image from a mobile device, performing recognition on the image to identify space-delimited strings, and generating a content graph for the image, the content graph having content nodes that represent at least some of the strings and the content graph having edges that represent a relative position of strings associated with the content nodes connected by the edges. The method may also include repeating the receiving, performing recognition, and generating for a plurality of images, the plurality of images belonging to a session, and generating a combined graph from the plurality of content graphs based on similarity of content nodes between content graphs, the combined graph representing text from the plurality of images in reading order.