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Accord.NET (logo) SimpleQuadrilateralTransformation Class
Performs quadrilateral transformation of an area in the source image.
Inheritance Hierarchy
SystemObject
  Accord.Imaging.FiltersBaseTransformationFilter
    Accord.Imaging.FiltersSimpleQuadrilateralTransformation

Namespace:  Accord.Imaging.Filters
Assembly:  Accord.Imaging (in Accord.Imaging.dll) Version: 3.4.0
Syntax
public class SimpleQuadrilateralTransformation : BaseTransformationFilter
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The SimpleQuadrilateralTransformation type exposes the following members.

Constructors
Properties
  NameDescription
Public propertyAutomaticSizeCalculaton
Automatic calculation of destination image or not.
Public propertyFormatTranslations
Format translations dictionary.
(Overrides BaseTransformationFilterFormatTranslations.)
Public propertyNewHeight
Height of the new transformed image.
Public propertyNewWidth
Width of the new transformed image.
Public propertySourceQuadrilateral
Quadrilateral's corners in source image.
Public propertyUseInterpolation
Specifies if bilinear interpolation should be used or not.
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Methods
  NameDescription
Public methodApply(Bitmap)
Apply filter to an image.
(Inherited from BaseTransformationFilter.)
Public methodApply(BitmapData)
Apply filter to an image.
(Inherited from BaseTransformationFilter.)
Public methodApply(UnmanagedImage)
Apply filter to an image in unmanaged memory.
(Inherited from BaseTransformationFilter.)
Public methodApply(UnmanagedImage, UnmanagedImage)
Apply filter to an image in unmanaged memory.
(Inherited from BaseTransformationFilter.)
Protected methodCalculateNewImageSize
Calculates new image size.
(Overrides BaseTransformationFilterCalculateNewImageSize(UnmanagedImage).)
Public methodEquals
Determines whether the specified object is equal to the current object.
(Inherited from Object.)
Protected methodFinalize
Allows an object to try to free resources and perform other cleanup operations before it is reclaimed by garbage collection.
(Inherited from Object.)
Public methodGetHashCode
Serves as the default hash function.
(Inherited from Object.)
Public methodGetType
Gets the Type of the current instance.
(Inherited from Object.)
Protected methodMemberwiseClone
Creates a shallow copy of the current Object.
(Inherited from Object.)
Protected methodProcessFilter
Process the filter on the specified image.
(Overrides BaseTransformationFilterProcessFilter(UnmanagedImage, UnmanagedImage).)
Public methodToString
Returns a string that represents the current object.
(Inherited from Object.)
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Fields
  NameDescription
Protected fieldnewHeight
New image height.
Protected fieldnewWidth
New image width.
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Extension Methods
  NameDescription
Public Extension MethodHasMethod
Checks whether an object implements a method with the given name.
(Defined by ExtensionMethods.)
Public Extension MethodToTOverloaded.
Converts an object into another type, irrespective of whether the conversion can be done at compile time or not. This can be used to convert generic types to numeric types during runtime.
(Defined by ExtensionMethods.)
Public Extension MethodToTOverloaded.
Converts an object into another type, irrespective of whether the conversion can be done at compile time or not. This can be used to convert generic types to numeric types during runtime.
(Defined by Matrix.)
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Remarks

The class implements simple algorithm described by Olivier Thill for transforming quadrilateral area from a source image into rectangular image. The idea of the algorithm is based on finding for each line of destination rectangular image a corresponding line connecting "left" and "right" sides of quadrilateral in a source image. Then the line is linearly transformed into the line in destination image.

Note Note
Due to simplicity of the algorithm it does not do any correction for perspective.

Note Note
To make sure the algorithm works correctly, it is preferred if the "left-top" corner of the quadrilateral (screen coordinates system) is specified first in the list of quadrilateral's corners. At least user need to make sure that the "left" side (side connecting first and the last corner) and the "right" side (side connecting second and third corners) are not horizontal.

Use QuadrilateralTransformation to avoid the above mentioned limitations, which is a more advanced quadrilateral transformation algorithms (although a bit more computationally expensive).

The image processing filter accepts 8 grayscale images and 24/32 bpp color images for processing.

Sample usage:

// 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
SimpleQuadrilateralTransformation filter =
    new SimpleQuadrilateralTransformation( corners, 200, 200 );
// apply the filter
Bitmap newImage = filter.Apply( image );

Initial image:

Result image:

See Also