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
C#
WinRT C#
WinRT JavaScript
C++

public class DiscreteFourierTransformCommand : Leadtools.ImageProcessing.RasterCommand, Leadtools.ImageProcessing.IRasterCommand

'Declaration
 
Public Class DiscreteFourierTransformCommand 
   Inherits Leadtools.ImageProcessing.RasterCommand
   Implements Leadtools.ImageProcessing.IRasterCommand

'Usage
 
Dim instance As DiscreteFourierTransformCommand

public sealed class DiscreteFourierTransformCommand : Leadtools.ImageProcessing.IRasterCommand

function Leadtools.ImageProcessing.Core.DiscreteFourierTransformCommand()

public ref class DiscreteFourierTransformCommand : public Leadtools.ImageProcessing.RasterCommand, Leadtools.ImageProcessing.IRasterCommand

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.

Example

Visual Basic
C#
WinRT C#
WinRT JavaScript
Silverlight C#
Silverlight VB

Public Sub DiscreteFourierTransformCommandExample()
   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 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)

End Sub

Public NotInheritable Class LEAD_VARS
   Public Const ImagesDir As String = "C:\Users\Public\Documents\LEADTOOLS Images"
End Class

public void DiscreteFourierTransformCommandExample()
   {
      // 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 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);

   }

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

function DiscreteFourierTransformCommandExample()
{
   var codecs = new Leadtools.Codecs.RasterCodecs();
   codecs.throwExceptionsOnInvalidImages = true;

   // Load the image
   var srcFileName = "Assets\\Image1.cmp";
   return Tools.AppInstallFolder().getFileAsync(srcFileName).then(function (loadFile) {
      return codecs.loadAsync(Leadtools.LeadStreamFactory.create(loadFile));
   }).then(function (image){
      // Prepare the command
      with (Leadtools.ImageProcessing.Core) {
         var FTArray = new FourierTransformInformation(image);
         var rcRange = Leadtools.LeadRectHelper.create(0, 0, image.width - 1, image.height - 1);
         var command = new DiscreteFourierTransformCommand();
         
         command.fourierTransformInformation = FTArray;
         command.range = rcRange;
         command.flags = DiscreteFourierTransformCommandFlags.discreteFourierTransform | 
            DiscreteFourierTransformCommandFlags.gray    | 
            DiscreteFourierTransformCommandFlags.range   | 
            DiscreteFourierTransformCommandFlags.insideX | 
            DiscreteFourierTransformCommandFlags.insideY;
         //Apply DFT.
         
         var disCommand = new FourierTransformDisplayCommand();
         disCommand.flags = FourierTransformDisplayCommandFlags.log | FourierTransformDisplayCommandFlags.magnitude;
         disCommand.fourierTransformInformation = command.fourierTransformInformation;
         // plot frequency magnitude
         disCommand.run(image);
      }
   });
}

[TestMethod]
public async Task DiscreteFourierTransformCommandExample()
{
   // Load an image
   RasterCodecs codecs = new RasterCodecs();
   codecs.ThrowExceptionsOnInvalidImages = true;
   // Load the image
   string srcFileName = @"Assets\Image1.cmp";
   StorageFile loadFile = await Tools.AppInstallFolder.GetFileAsync(srcFileName);
   RasterImage image = await codecs.LoadAsync(LeadStreamFactory.Create(loadFile));

   // Prepare the command
   FourierTransformInformation FTArray = new FourierTransformInformation(image);
   LeadRect rcRange = LeadRectHelper.Create(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);

}

Requirements

Target Platforms: Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2

Reference