Rectification of characters and text as transform invariant low-rank textures
First Claim
1. A method for rectifying text in an image, comprising using a computing device to perform steps for:
- receiving a single input image;
selecting a single region of the input image containing deformed text;
iteratively processing the selected region using an iterative convex optimization process that models the selected region as a low-rank matrix and repeatedly estimates and updates transforms that would cause the deformation of the text in the modeled region until a rank of the matrix is minimized; and
recovering a low-rank texture from the selected image region using the estimated transforms associated with the minimized rank to construct a low-rank texture version of the selected region from which the deformations have been removed from the text and wherein the text has been rectified to an upright position.
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Abstract
A “Text Rectifier” provides various techniques for processing selected regions of an image containing text or characters by treating those images as matrices of low-rank textures and using a rank minimization technique that recovers and removes image deformations (e.g., affine and projective transforms as well as general classes of nonlinear transforms) while rectifying the text or characters in the image region. Once distortions have been removed and the text or characters rectified, the resulting text is made available for a variety of uses or further processing such as optical character recognition (OCR). In various embodiments, binarization and/or inversion techniques are applied to the selected image regions during the rank minimization process to both improve text rectification and to present the resulting images of text to an OCR engine in a form that enhances the accuracy of the OCR results.
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Citations
20 Claims
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1. A method for rectifying text in an image, comprising using a computing device to perform steps for:
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receiving a single input image; selecting a single region of the input image containing deformed text; iteratively processing the selected region using an iterative convex optimization process that models the selected region as a low-rank matrix and repeatedly estimates and updates transforms that would cause the deformation of the text in the modeled region until a rank of the matrix is minimized; and recovering a low-rank texture from the selected image region using the estimated transforms associated with the minimized rank to construct a low-rank texture version of the selected region from which the deformations have been removed from the text and wherein the text has been rectified to an upright position. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A system for modeling an image containing text as a low-rank texture in order to rectify the text, comprising:
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a general purpose computing device; and a computer program comprising program modules executable by the computing device, wherein the computing device is directed by the program modules of the computer program to; receive a single input image; select a single region of the input image containing deformed text; perform binarization of the selected image region that makes the selected image region white text on a black background prior to performing each iteration of a convex optimization process; iteratively process the selected region using the iterative convex optimization process that models the selected region as a low-rank matrix and repeatedly estimates and updates transforms that would cause the deformation of the text in the modeled region until a rank of the matrix is minimized; and recover a low-rank texture from the selected image region using the estimated transforms associated with the minimized rank to construct a low-rank texture version of the selected region from which the deformations have been removed from the text and wherein the text has been rectified to an upright position. - View Dependent Claims (9, 10, 11, 12, 13)
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14. A computer-readable storage device having computer executable instructions stored therein for extracting low-rank textural and geometric information and a sparse error component from an image, said instructions comprising:
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receiving a single input image; selecting a single region of the input image containing deformed text; converting the selected image region to a binary image prior to performing each iteration of a convex optimization process; iteratively processing the selected region using the iterative convex optimization process that models the selected region as a low-rank matrix and repeatedly estimates and updates transforms that would cause the deformation of the text in the modeled region until a rank of the matrix is minimized; and recovering a low-rank texture from the selected image region using the estimated transforms associated with the minimized rank to construct a low-rank texture version of the selected region from which the deformations have been removed from the text and wherein the text has been rectified to an upright position. - View Dependent Claims (15, 16, 17, 18, 19, 20)
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Specification