Document comparison and analysis
First Claim
1. A computerized method comprising:
- a. obtaining a first digital image of a first document page;
b. obtaining a second digital image of a second document page;
c. performing global geometrical transformation on at least one of said first and second digital images to obtain first and second aligned digital images;
d. selecting a window of said first aligned digital image;
e. selecting a window of said second aligned digital image;
f. estimating residual local geometrical shifts, radiometric differences and blurring differences between said selected windows to obtain a second transformation;
g. applying said second transformation to at least one of said windows;
h. repeating steps (d) through (g) for consecutive windows of said first and second aligned images to obtain first and second similar images;
i. comparing said first and second similar images to obtain a difference image;
j. analyzing said difference image to determine whether at least one of the group consisting of;
characters, images and components thereof have been added, deleted, changed or shifted; and
k. displaying said differences.
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Abstract
A method including a process by which a first digital image of the document is obtained. A second digital image of a document is retrieved from a computer, a mobile device, a computer network or by imaging of a second document. The method includes calculating the transformation between the first and second digital images such as geometrical distortion, local ‘brightness and contrast differences and blurring due to the optical imaging process. The method estimates the parameters of these transformations so that the transformations can be applied to one of the images, rendering it as similar as possible to the other image. The method further compares the two images in order to find differences such as addition, deletion or changing of characters or words.
The method further displays the differences on a display such as a computer screen or mobile device screen or reports to the user that the two documents are identical.
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Citations
48 Claims
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1. A computerized method comprising:
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a. obtaining a first digital image of a first document page; b. obtaining a second digital image of a second document page; c. performing global geometrical transformation on at least one of said first and second digital images to obtain first and second aligned digital images; d. selecting a window of said first aligned digital image; e. selecting a window of said second aligned digital image; f. estimating residual local geometrical shifts, radiometric differences and blurring differences between said selected windows to obtain a second transformation; g. applying said second transformation to at least one of said windows; h. repeating steps (d) through (g) for consecutive windows of said first and second aligned images to obtain first and second similar images; i. comparing said first and second similar images to obtain a difference image; j. analyzing said difference image to determine whether at least one of the group consisting of;
characters, images and components thereof have been added, deleted, changed or shifted; andk. displaying said differences. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24)
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25. A system comprising:
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a processor; communication means connected with the processor; display means; means for obtaining a first digital image of a first document page; means for obtaining a second digital image of a second document page; and memory means coupled to the processor, said memory means configured to store a plurality of modules for execution by the processor, the plurality of modules comprising; logic for performing global geometrical transformation on at least one of first and second digital images to obtain first and second aligned digital images; logic for selecting a window of said first aligned digital image; logic for selecting a window of said second aligned digital image; logic for estimating local residual geometrical shifts, radiometric differences and blurring differences between said selected windows to obtain a second transformation; logic for applying said second transformation to at least one of said windows; logic for repeating said estimating and applying for consecutive windows of said first and second aligned images to obtain first and second similar images; logic for comparing said first and second similar images to obtain a difference image; logic for analyzing said difference image to determine whether one or more characters have been added, deleted, changed or shifted; and logic for displaying said changes between the images. - View Dependent Claims (26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48)
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Specification