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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 
Managed Extensions for C++ 
public __gc class DiscreteFourierTransformCommand : public RasterCommand, IRasterCommand 
C++/CLI 
public ref class DiscreteFourierTransformCommand : public RasterCommand, IRasterCommand 

Example

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

      Dim leadImage As RasterImage = codecs.Load("C:\Program Files\LEAD Technologies\LEADTOOLS 15\Images\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
ImageProcessing.Core.DiscreteFourierTransformCommand 
      public void DiscreteFourierTransformCommandExample() 
      { 
         // Load an image 
         RasterCodecs.Startup(); 
         RasterCodecs codecs = new RasterCodecs(); 
         codecs.ThrowExceptionsOnInvalidImages = true; 
 
         RasterImage image = codecs.Load(@"C:\Program Files\LEAD Technologies\LEADTOOLS 15\Images\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.
  • 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