DiscreteFourierTransformCommand Class

Computes the Discrete Fourier transform of an image or the Inverse Discrete Fourier transform as specified by the flags.

Object Model

Syntax

C#
Visual Basic
WinRT C#
Java
Objective-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

@interface LTDiscreteFourierTransformCommand : LTRasterCommand

function Leadtools.ImageProcessing.Core.DiscreteFourierTransformCommand()

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

Remarks

This command is available in the Imaging Pro and above toolkits.

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.
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.

*Calculating Master Channel Values

In order to speed up widely used image processing filters in LEADTOOLS, the grayscale value (master channel) of a colored image is calculated using the following formulas:

            #define CalcGrayValue(r, g, b) ((L_UCHAR)(((L_UCHAR) (((2 * (L_UINT) (r)) + (5 * (L_UINT) (g)) + (L_UINT) (b) + 4) / 8))))
            #define CalcGrayValue16(r, g, b) ((L_UINT16) (((2 * (L_UINT32) (r)) + (5 * (L_UINT32) (g)) + (L_UINT32) (b) + 4) / 8))
            #define CalcGrayValue32(r, g, b) ((L_UINT32) (((2 * (L_UINT32) (r)) + (5 * (L_UINT32) (g)) + (L_UINT32) (b) + 4) / 8))

For more information, refer to Removing Noise.

Example

Run the DiscreteFourierTransformCommand on an image.

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

Copy Code

Imports Leadtools
Imports Leadtools.Codecs
Imports Leadtools.ImageProcessing.Core

   
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

using Leadtools;
using Leadtools.Codecs;
using Leadtools.ImageProcessing.Core;

      
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);
      }
   });
}

using Leadtools;
using Leadtools.Codecs;
using Leadtools.ImageProcessing.Core;

      
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

Reference