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DiscreteFourierTransformCommand Class
See Also  Members   Example 
Leadtools.ImageProcessing.Core Namespace : DiscreteFourierTransformCommand Class



Computes the Discrete Fourier transform of an image or the Inverse Discrete Fourier transform as specified by the flags. This command is available in the Raster Pro and above toolkits.

Object Model


Syntax

Visual Basic (Declaration) 
Public Class DiscreteFourierTransformCommand 
   Inherits RasterCommand
   Implements IRasterCommand 
Visual Basic (Usage)Copy Code
Dim instance As DiscreteFourierTransformCommand
C# 
public class DiscreteFourierTransformCommand : RasterCommand, IRasterCommand 
C++/CLI 
public ref class DiscreteFourierTransformCommand : public RasterCommand, IRasterCommand 

Example

Run the DiscreteFourierTransformCommand on an image.

Visual BasicCopy Code
Public Sub DiscreteFourierTransformCommandExample()
   RasterCodecs.Startup()
   Dim codecs As New RasterCodecs()
   codecs.ThrowExceptionsOnInvalidImages = True

   Dim leadImage As RasterImage = codecs.Load(LeadtoolsExamples.Common.ImagesPath.Path + "Master.jpg")

   ' Prepare the command
   Dim FTArray As FourierTransformInformation = New FourierTransformInformation(leadImage)
   Dim rcRange As Rectangle = New Rectangle(0, 0, leadImage.Width - 1, leadImage.Height - 1)
   Dim command As DiscreteFourierTransformCommand = New DiscreteFourierTransformCommand

   command.FourierTransformInformation = FTArray
   command.Range = rcRange
   command.Flags = DiscreteFourierTransformCommandFlags.DiscreteFourierTransform Or _
      DiscreteFourierTransformCommandFlags.Gray Or _
      DiscreteFourierTransformCommandFlags.Range Or _
      DiscreteFourierTransformCommandFlags.InsideX Or _
      DiscreteFourierTransformCommandFlags.InsideY
   'Apply DFT.
   command.Run(leadImage)

   Dim disCommand As FourierTransformDisplayCommand = New FourierTransformDisplayCommand
   disCommand.Flags = FourierTransformDisplayCommandFlags.Log Or FourierTransformDisplayCommandFlags.Magnitude
   disCommand.FourierTransformInformation = command.FourierTransformInformation
   'plot frequency magnitude
   disCommand.Run(leadImage)

   RasterCodecs.Shutdown()
End Sub
C#Copy Code
public void DiscreteFourierTransformCommandExample() 
{ 
   // Load an image 
   RasterCodecs.Startup(); 
   RasterCodecs codecs = new RasterCodecs(); 
   codecs.ThrowExceptionsOnInvalidImages = true; 
 
   RasterImage image = codecs.Load(LeadtoolsExamples.Common.ImagesPath.Path + "Master.jpg"); 
 
   // Prepare the command 
   FourierTransformInformation FTArray = new FourierTransformInformation(image); 
   Rectangle rcRange = new Rectangle(0, 0, image.Width - 1, image.Height - 1); 
   DiscreteFourierTransformCommand command = new DiscreteFourierTransformCommand(); 
 
   command.FourierTransformInformation = FTArray; 
   command.Range = rcRange; 
   command.Flags = DiscreteFourierTransformCommandFlags.DiscreteFourierTransform |  
      DiscreteFourierTransformCommandFlags.Gray    |  
      DiscreteFourierTransformCommandFlags.Range   |  
      DiscreteFourierTransformCommandFlags.InsideX |  
      DiscreteFourierTransformCommandFlags.InsideY; 
   //Apply DFT. 
 
   FourierTransformDisplayCommand disCommand = new FourierTransformDisplayCommand(); 
   disCommand.Flags = FourierTransformDisplayCommandFlags.Log|  FourierTransformDisplayCommandFlags.Magnitude; 
   disCommand.FourierTransformInformation = command.FourierTransformInformation; 
   // plot frequency magnitude 
   disCommand.Run(image); 
 
   RasterCodecs.Shutdown(); 
}

Remarks

  • This command converts the image from the time domain to the frequency domain and vice versa using the Discrete Fourier Transform algorithm. Use the FastFourierTransformCommand to use a Fast Fourier Transform algorithm on an image. Please note however, that this command does not impose the size restrictions (the width and height having to be powers of 2) that the Fast Fourier Transform method, FastFourierTransformCommand, imposes upon images.
  • Before using this command, you need to construct an instance from FourierTransformInformation.
  • The image can be transformed back into the original image minus the noise using the InverseDiscreteFourierTransform
  • This command does not work on regions. If the image has a region the command ignores it and processes the entire image.
  • This command does not support 12 and 16-bit grayscale and 48 and 64-bit color images. If the image is 12 and 16-bit grayscale and 48 and 64-bit color, the method will not threw an exception.
  • This command does not support 32-bit grayscale images.
  • This command does not support signed images.
For more information, refer to Removing Noise.

Inheritance Hierarchy

System.Object
   Leadtools.ImageProcessing.RasterCommand
      Leadtools.ImageProcessing.Core.DiscreteFourierTransformCommand

Requirements

Target Platforms: Microsoft .NET Framework 2.0, Windows 98, Windows NT 4.0, Windows Millennium Edition, Windows 2000, Windows XP Home Edition, Windows XP Professional, Windows Server 2003 family

See Also