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Quadrilateral transformation and finding

AForge.NET framework provides set of set of image processing classes, which
allow doing quadrilateral transformation and finding quadrilateral’s corners.

Source image

Quadrilateral Transformation

The class implements quadrilateral transformation algorithm, which extracts any quadrilateral from the
specified source image and puts it into rectangular destination image.

// define quadrilateral's corners
List<IntPoint> corners = new List<IntPoint>( );
corners.Add( new IntPoint(  99,  99 ) );
corners.Add( new IntPoint( 156,  79 ) );
corners.Add( new IntPoint( 184, 126 ) );
corners.Add( new IntPoint( 122, 150 ) );
// create filter
QuadrilateralTransformation filter =
    new QuadrilateralTransformationBilinear( corners, 200, 200 );
// apply the filter
Bitmap newImage = filter.Apply( image );

Backward Quadrilateral Transformation

The class implements backward quadrilateral transformation algorithm, which allows to transform any rectangular image into any
quadrilateral area in a given destination image.

// define quadrilateral's corners
List<IntPoint> corners = new List<IntPoint>( );
corners.Add( new IntPoint(  99,  99 ) );
corners.Add( new IntPoint( 156,  79 ) );
corners.Add( new IntPoint( 184, 126 ) );
corners.Add( new IntPoint( 122, 150 ) );
// create filter
BackwardQuadrilateralTransformation filter =
    new BackwardQuadrilateralTransformation( sourceImage, corners );
// apply the filter
Bitmap newImage = filter.Apply( image );

Quadrilateral Finder

In order to allow finding corners of quadrilateral area the framework provides the
QuadrilateralFinder
class, which processes image searching for objects corners. It is assumed that object consists of none black pixel (all black is background).

// get corners of the quadrilateral
QuadrilateralFinder qf = new QuadrilateralFinder( );
List<IntPoint> corners = qf.ProcessImage( image );

Once corners are found the above mentioned classes for quadrilateral transformation can be used.