Results 1 - 10
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30
Restoration of archival documents using a wavelet technique
- IEEE Trans. on Pattern Analysis and Machine Intelligence
, 2002
"... Abstract—This paper addresses a problem of restoring handwritten archival documents by recovering their contents from the interfering handwriting on the reverse side caused by the seeping of ink. We present a novel method that works by first matching both sides of a document such that the interferin ..."
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Cited by 34 (8 self)
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Abstract—This paper addresses a problem of restoring handwritten archival documents by recovering their contents from the interfering handwriting on the reverse side caused by the seeping of ink. We present a novel method that works by first matching both sides of a document such that the interfering strokes are mapped with the corresponding strokes originating from the reverse side. This facilitates the identification of the foreground and interfering strokes. A wavelet reconstruction process then iteratively enhances the foreground strokes and smears the interfering strokes so as to strengthen the discriminating capability of an improved Canny edge detector against the interfering strokes. The method has been shown to restore the documents effectively with average precision and recall rates for foreground text extraction at 84 percent and 96 percent, respectively. Index Terms—Document image analysis, wavelet enhancement, wavelet smearing, Canny edge detector, text extraction, image segmentation, bleedthrough, show-through, noise cancellation, denoising. 1
Comparison of some thresholding algorithms for text/background segmentation in difficult document images
- 7 th ICDAR Conference, 2003
, 2003
"... A number of techniques have previously been proposed for effective thresholding of document images. In this paper two new thresholding techniques are proposed and compared against some existing algorithms. The algorithms were evaluated on four types of ‘difficult ’ document images where considerable ..."
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Cited by 31 (0 self)
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A number of techniques have previously been proposed for effective thresholding of document images. In this paper two new thresholding techniques are proposed and compared against some existing algorithms. The algorithms were evaluated on four types of ‘difficult ’ document images where considerable background noise or variation in contrast and illumination exists. The quality of the thresholding was assessed using the Precision and Recall analysis of the resultant words in the foreground. The conclusion is that no single algorithm works well for all types of image but some work better than others for particular types of images suggesting that improved performance can be obtained by automatic selection or combination of appropriate algorithm(s) for the type of document image under investigation. 1.
Correcting document image warping based on regression of curved text lines
- in Proceedings of the International Conference on Document Analysis and Recognition
, 2003
"... Image warping is a common problem when one scans or photocopies a document page from a thick bound volume, resulting in shading and curved text lines in the spine area of the bound volume. This will not only impair readability, but will also reduce the OCR accuracy. Further to our earlier attempt to ..."
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Cited by 27 (6 self)
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Image warping is a common problem when one scans or photocopies a document page from a thick bound volume, resulting in shading and curved text lines in the spine area of the bound volume. This will not only impair readability, but will also reduce the OCR accuracy. Further to our earlier attempt to correct such images, this paper proposes a simpler connected component analysis and regression technique. Compared to our earlier method, the present system is computationally less expensive and is resolution independent too. The implementation of the new system and improvement of OCR accuracy are presented in this paper. 1.
Restoring Warped Document Images through 3D Shape Modeling
- IEEE Trans. Pattern Analysis and Machine Intelligence
, 2006
"... Abstract—Scanning a document page from a thick bound volume often results in two kinds of distortions in the scanned image, i.e., shade along the “spine ” of the book and warping in the shade area. In this paper, we propose an efficient restoration method based on the discovery of the 3D shape of a ..."
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Cited by 23 (0 self)
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Abstract—Scanning a document page from a thick bound volume often results in two kinds of distortions in the scanned image, i.e., shade along the “spine ” of the book and warping in the shade area. In this paper, we propose an efficient restoration method based on the discovery of the 3D shape of a book surface from the shading information in a scanned document image. From a technical point of view, this shape from shading (SFS) problem in real-world environments is characterized by 1) a proximal and moving light source, 2) Lambertian reflection, 3) nonuniform albedo distribution, and 4) document skew. Taking all these factors into account, we first build practical models (consisting of a 3D geometric model and a 3D optical model) for the practical scanning conditions to reconstruct the 3D shape of the book surface. We next restore the scanned document image using this shape based on deshading and dewarping models. Finally, we evaluate the restoration results by comparing our estimated surface shape with the real shape as well as the OCR performance on original and restored document images. The results show that the geometric and photometric distortions are mostly removed and the OCR results are improved markedly. Index Terms—Document image restoration, document image analysis, shape from shading, image warping, image distortion, OCR improvement. 1
Matching of double-sided document images to remove interference
- in IEEE Conference on Computer Vision and Pattern Recognition
, 2001
"... The National Archives of Singapore keeps a large volume of historical handwritten documents. One common problem with the archives is that over the years, ink sipped through the pages of these documents such that characters on the reverse side become visible and interfere with the characters on the f ..."
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Cited by 21 (6 self)
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The National Archives of Singapore keeps a large volume of historical handwritten documents. One common problem with the archives is that over the years, ink sipped through the pages of these documents such that characters on the reverse side become visible and interfere with the characters on the front side. This paper addresses this problem and develops a novel algorithm to extract clear textual images from the interference. We achieve this by mapping images from both sides of a page such that interfering strokes seen on the front side are matched with the strokes originating from the reverse side so as to achieve a cancellation effect. The resultant image is further subjected to an improved Canny edge detection to eliminate remaining background interference. Experimental results have confirmed the validity of our proposed method. 1.
IODetector: A generic service for indoor outdoor detection
- In SenSys’ 12
"... The location and context switching, especially the indoor/outdoor switching, provides essential and primitive information for upper layer mobile applications. In this paper, we present IODetector: a lightweight sensing service which runs on the mobile phone and detects the indoor/outdoor environment ..."
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Cited by 19 (5 self)
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The location and context switching, especially the indoor/outdoor switching, provides essential and primitive information for upper layer mobile applications. In this paper, we present IODetector: a lightweight sensing service which runs on the mobile phone and detects the indoor/outdoor environment in a fast, accurate, and efficient manner. Constrained by the energy budget, IODetector leverages primarily lightweight sensing resources including light sensors, magnetism sensors, celltower signals, etc. For universal applicability, IODetector assumes no prior knowledge (e.g., fingerprints) of the environment and uses only on-board sensors common to mainstream mobile phones. Being a generic and lightweight service component, IODetector greatly benefits many location-based and context-aware applications. We prototype the IODetector on Android mobile phones and evaluate the system comprehensively with data collected from 19 traces which include 84 different places during one month period, employing different phone models. We further perform a case study where we make use of IODetector to instantly infer the GPS availability and localization accuracy in different indoor/outdoor environments.
Restoration of curved document images through 3d shape modeling
- In International Conference on Computer Vision and Pattern Recognition (CVPR2004
, 2004
"... In this paper, we address the problem of discovering the 3D shape of a book surface from the shading information in a scanned document image. This shapefrom-shading problem is characterized in real world environments by a proximal and a moving light source, Lambertian reflection and a non-uniform al ..."
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Cited by 19 (2 self)
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In this paper, we address the problem of discovering the 3D shape of a book surface from the shading information in a scanned document image. This shapefrom-shading problem is characterized in real world environments by a proximal and a moving light source, Lambertian reflection and a non-uniform albedo distribution. By considering all these factors, we first build the practical model (consists of geometric model and optical model) to reconstruct the 3D shape of book surface. We next restore the scanned image using this shape based on two models, namely de-shading and dewarping models. Finally, we compare the OCR results on the original and restored document image. The experiments show that the geometric and photometric distortions are mostly removed and the OCR results are improved markedly. 1.
Document image enhancement using directional wavelet
- in Proceedings of the 2003 IEEE Conference on Computer Vision and Pattern Recognition
, 2003
"... This paper proposes a novel algorithm to clean up a large collection of historical handwritten documents kept in the National Archives of Singapore. Due to the seepage of ink over long period of storage, the front page of each document has been severely marred by the reverse side writing. Earlier at ..."
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Cited by 13 (0 self)
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This paper proposes a novel algorithm to clean up a large collection of historical handwritten documents kept in the National Archives of Singapore. Due to the seepage of ink over long period of storage, the front page of each document has been severely marred by the reverse side writing. Earlier attempts have been made to match both sides of a page to identify the offending strokes originating from the back so as to eliminate them with the aid of a wavelet transform. Perfect matching, however, is difficult due to document skews, differing resolutions, inadvertently missing out reverse side and warped pages during image capture. A new approach is now proposed to do away with double side mapping by using a directional wavelet transform that is able to distinguish the foreground and reverse side strokes much better than the conventional wavelet transform. Experiments have shown that the method indeed enhances the readability of each document significantly after the directional wavelet operation without the need for mapping with its reverse side. 1.
Color Binarization for complex camera-based images
- Proc. of the Electronic Imaging Conference of SPIE/IS&T, 2005
"... This paper describes a new automatic color thresholding based on wavelet denoising and color clustering with K-means in order to segment text information in a camera-based image. Several parameters bring different information and this paper tries to explain how to use this complementarity. It is mai ..."
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Cited by 10 (1 self)
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This paper describes a new automatic color thresholding based on wavelet denoising and color clustering with K-means in order to segment text information in a camera-based image. Several parameters bring different information and this paper tries to explain how to use this complementarity. It is mainly based on the discrimination between two kinds of backgrounds: clean or complex. On one hand, this separation is useful to apply a particular algorithm on each of these cases and on the other hand to decrease the computation time for clean cases for which a faster method could be considered. Finally, several experiments were done to discuss results and to conclude that the use of a discrimination between kinds of backgrounds gives better results in terms of Precision and Recall.
Removal of interfering strokes in double-sided document images
- IEEE Workshop on the Application of Computer Vision, WACV2000
, 2000
"... This paper addresses a special problem with historical document images where handwritten characters from the reverse side appear as noise on the front side and even interfere with the front side characters. A novel method to extract clear textual images from interfering and overlapping areas of text ..."
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Cited by 9 (3 self)
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This paper addresses a special problem with historical document images where handwritten characters from the reverse side appear as noise on the front side and even interfere with the front side characters. A novel method to extract clear textual images from interfering and overlapping areas of text is presented here. The proposed algorithm is interesting in that, with an observation that the edges of the sipping strokes from the reverse side are not as sharp as those on the front side, it adopts an edge detection approach to suppress unwanted background patterns. By further concentrating on the orientation of the strokes, other remaining long and strong noisy edges are removed by using an orientation filter and a size filter. The proposed method proves to perform well regardless of the intensity differences between the foreground writing and the interfering strokes. The segmentation results of real images are shown and evaluated.
