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FourierTransformDisplayCommand Class
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Leadtools.ImageProcessing.Core Namespace : FourierTransformDisplayCommand Class



This command is used to display the results of a Fast Fourier Transform or a Discrete Fourier analysis as an image. This command is available in the Raster Pro and above toolkits.

Object Model

FourierTransformDisplayCommand ClassFourierTransformInformation Class

Syntax

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

Example

Runs the Leadtools.ImageProcessing.Core.FourierTransformDisplayCommand on an image, applies the Discrete Fourier Transform command to it, and displays the data.

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

   Dim leadImage As RasterImage = codecs.Load(Path.Combine(LEAD_VARS.ImagesDir, "Master.jpg"))

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

   DFTcommand.FourierTransformInformation = FTArray
   DFTcommand.Range = rcRange
   DFTcommand.Flags = DiscreteFourierTransformCommandFlags.DiscreteFourierTransform _
   Or DiscreteFourierTransformCommandFlags.Gray _
   Or DiscreteFourierTransformCommandFlags.Range _
   Or DiscreteFourierTransformCommandFlags.InsideX _
   Or DiscreteFourierTransformCommandFlags.OutsideY
   ' apply DFT
   DFTcommand.Run(leadImage)

   command.Flags = FourierTransformDisplayCommandFlags.Log Or FourierTransformDisplayCommandFlags.Magnitude
   command.FourierTransformInformation = FTArray
   'plot frequency magnitude
   command.Run(leadImage)

End Sub

Public NotInheritable Class LEAD_VARS
   Public Const ImagesDir As String = "C:\Users\Public\Documents\LEADTOOLS Images"
End Class
C#Copy Code
public void FourierTransformDisplayCommandExample()
   {
      // Load an image
      RasterCodecs codecs = new RasterCodecs();
      codecs.ThrowExceptionsOnInvalidImages = true;

      RasterImage image = codecs.Load(Path.Combine(LEAD_VARS.ImagesDir, "Master.jpg"));

      // Prepare the command
      FourierTransformInformation FTArray = new FourierTransformInformation(image);
      LeadRect rcRange = new LeadRect(0, 0, image.Width - 1, image.Height - 1);
      DiscreteFourierTransformCommand DFTcommand = new DiscreteFourierTransformCommand();
      FourierTransformDisplayCommand  command = new FourierTransformDisplayCommand();

      DFTcommand.FourierTransformInformation = FTArray;
      DFTcommand.Range = rcRange;
      DFTcommand.Flags = DiscreteFourierTransformCommandFlags.DiscreteFourierTransform | 
         DiscreteFourierTransformCommandFlags.Gray    | 
         DiscreteFourierTransformCommandFlags.Range   | 
         DiscreteFourierTransformCommandFlags.InsideX | 
         DiscreteFourierTransformCommandFlags.InsideY; 
      // apply DFT
      DFTcommand.Run(image);

      command.Flags = FourierTransformDisplayCommandFlags.Log | FourierTransformDisplayCommandFlags.Magnitude;
      command.FourierTransformInformation = FTArray;
      //plot frequency magnitude.
      command.Run(image);

   }

static class LEAD_VARS
{
   public const string ImagesDir = @"C:\Users\Public\Documents\LEADTOOLS Images";
}
SilverlightCSharpCopy Code


SilverlightVBCopy Code


 
            
            
Remarks
    
    
  • This command converts the Data property of the FourierTransformInformation object computed by FastFourierTransformCommand or FastFourierTransformCommand commands into an image. The resulting image may be displayed such that it shows either the frequency harmonics amplitude data or phase data. The (0,0) frequency is located in the image center, positive X harmonics in the right half and positive Y harmonics located in the lower half of the image.
    • 

    
  • This command does not work on regions. If the image has a region the command ignores it and processes the entire image.
    • 

    
  • The Run method image should be allocated prior to calling this command. The size of the image must be the same size as the image that was used to generate the information in the Data property of the FourierTransformInformation object.
    • 

    
  • 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 command will not threw an exception.
    • 

    
  • This command does not support signed data images.
    • 

    
  • This command does not support 32-bit grayscale images.
    • 

For more information, refer to Removing Noise.

            
Inheritance Hierarchy
System.Object
   Leadtools.ImageProcessing.RasterCommand
      Leadtools.ImageProcessing.Core.FourierTransformDisplayCommand
 
            
Requirements
Target Platforms: Silverlight 3.0, Windows XP, Windows Server 2003 family, Windows Server 2008 family, Windows Vista, Windows 7, MAC OS/X (Intel Only) 

            
            
See Also