C# Class Accord.Imaging.DocumentSkewChecker

Skew angle checker for scanned documents.

The class implements document's skew checking algorithm, which is based on Hough line transformation. The algorithm is based on searching for text base lines - black line of text bottoms' followed by white line below.

The routine supposes that a white-background document is provided with black letters. The algorithm is not supposed for any type of objects, but for document images with text.

The range of angles to detect is controlled by MaxSkewToDetect property.

The filter accepts 8 bpp grayscale images for processing.

Sample usage:

 // create instance of skew checker DocumentSkewChecker skewChecker = new DocumentSkewChecker( ); // get documents skew angle double angle = skewChecker.GetSkewAngle( documentImage ); // create rotation filter RotateBilinear rotationFilter = new RotateBilinear( -angle ); rotationFilter.FillColor = Color.White; // rotate image applying the filter Bitmap rotatedImage = rotationFilter.Apply( documentImage );

Initial image:

Deskewed image:

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Private Properties

Property	Type	Description
CollectLines	void
GetMostIntensiveLines	Accord.Imaging.HoughLine[]
InitHoughMap	void

Public Methods

Method	Description
DocumentSkewChecker ( ) : System	Initializes a new instance of the DocumentSkewChecker class.
GetSkewAngle ( Bitmap image ) : double	Get skew angle of the provided document image.
GetSkewAngle ( Bitmap image, Rectangle rect ) : double	Get skew angle of the provided document image.
GetSkewAngle ( BitmapData imageData ) : double	Get skew angle of the provided document image.
GetSkewAngle ( BitmapData imageData, Rectangle rect ) : double	Get skew angle of the provided document image.
GetSkewAngle ( UnmanagedImage image ) : double	Get skew angle of the provided document image.
GetSkewAngle ( UnmanagedImage image, Rectangle rect ) : double	Get skew angle of the provided document image.

Private Methods

Method	Description
CollectLines ( short minLineIntensity ) : void
GetMostIntensiveLines ( int count ) : Accord.Imaging.HoughLine[]
InitHoughMap ( ) : void

Method Details

DocumentSkewChecker() public method

Initializes a new instance of the DocumentSkewChecker class.

public DocumentSkewChecker ( ) : System
return	System