FastFourierTransformCommand Class

Computes the Fast Fourier transform of an image or the Inverse Fast Fourier transform as specified by 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 FastFourierTransformCommand : Leadtools.ImageProcessing.RasterCommand, Leadtools.ImageProcessing.IRasterCommand

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

'Usage
 
Dim instance As FastFourierTransformCommand

public sealed class FastFourierTransformCommand : Leadtools.ImageProcessing.IRasterCommand

function Leadtools.ImageProcessing.Core.FastFourierTransformCommand()

public ref class FastFourierTransformCommand : 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 a Fast Fourier Transform algorithm. Fast Fourier Transform algorithms are a simplification of a Discrete Fourier Transform and require that the image dimensions must be power of two (i.e. 2, 4, 8, 16, 32_etc). The number of computations needed are reduced from 2N2 to 2N LgN. Use the DiscreteFourierTransformCommand to use a Discrete Fourier Transform algorithm on an image. If you try to use this method with an image with dimensions that are not a power of two, the method will return an ERROR_INV_PARAMETER error.
Before using this command, you must create an instance of FourierTransformInformation
The image can be transformed back into the original image minus the noise using the InverseFastFourierTransform
This command does not work on regions. If the image has a region the method 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 command will not threw an exception.
This command does not support 32-bit grayscale images.

For more information, refer to Removing Noise.

Example

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

Public Sub FastFourierTransformCommandExample()
   Dim codecs As New RasterCodecs()
   codecs.ThrowExceptionsOnInvalidImages = True

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

   ' Prepare the command
   ' Resize the image to make sure the image's dimensions are power of two.
   Dim sizecommand As SizeCommand = New SizeCommand(256, 256, RasterSizeFlags.Bicubic)

   sizecommand.Run(leadImage)

   Dim FTArray As FourierTransformInformation = New FourierTransformInformation(leadImage)
   ' Apply FFT.
   Dim command As FastFourierTransformCommand = New FastFourierTransformCommand(FTArray, FastFourierTransformCommandFlags.FastFourierTransform Or FastFourierTransformCommandFlags.Gray)

   command.Run(leadImage)
   Dim rcRect As LeadRect = New LeadRect(0, 0, leadImage.Width \ 2, leadImage.Height \ 2)
   Dim FreqCommand As FrequencyFilterCommand = New FrequencyFilterCommand(FTArray, rcRect, FrequencyFilterCommandFlags.InsideX Or FrequencyFilterCommandFlags.OutsideY)

   Dim InvCommand As FastFourierTransformCommand = New FastFourierTransformCommand(FTArray, FastFourierTransformCommandFlags.InverseFastFourierTransform Or FastFourierTransformCommandFlags.Gray Or FastFourierTransformCommandFlags.Scale Or FastFourierTransformCommandFlags.Both)

   InvCommand.Run(leadImage)

End Sub

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

public void FastFourierTransformCommandExample()
   {
      // Load an image
      RasterCodecs codecs = new RasterCodecs();
      codecs.ThrowExceptionsOnInvalidImages = true;

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

      // Prepare the command
      // Resize the image to make sure the image's dimensions are power of two.
      SizeCommand sizecommand = new SizeCommand(256, 256, Leadtools.RasterSizeFlags.Bicubic);

      sizecommand.Run(image);

      FourierTransformInformation FTArray = new FourierTransformInformation(image);
      // Apply FFT.
      FastFourierTransformCommand command = new FastFourierTransformCommand(FTArray, FastFourierTransformCommandFlags.FastFourierTransform |  FastFourierTransformCommandFlags.Gray);
      command.Run(image);
      LeadRect rcRect = new LeadRect(0, 0, image.Width / 2, image.Height / 2);
      FrequencyFilterCommand FreqCommand = new FrequencyFilterCommand(FTArray, rcRect, FrequencyFilterCommandFlags.InsideX | FrequencyFilterCommandFlags.OutsideY);

      FastFourierTransformCommand InvCommand = new FastFourierTransformCommand(FTArray, FastFourierTransformCommandFlags.InverseFastFourierTransform |  FastFourierTransformCommandFlags.Gray | FastFourierTransformCommandFlags.Scale | FastFourierTransformCommandFlags.Both);
      InvCommand.Run(image);

   }

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

function FastFourierTransformCommandExample()
{
   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) {
         // Resize the image to make sure the image's dimensions are power of two.
         var sizecommand = new Leadtools.ImageProcessing.SizeCommand(256, 256, Leadtools.RasterSizeFlags.bicubic);
         
         sizecommand.run(image);
            
         var FTArray = new FourierTransformInformation(image);
         // Apply FFT.
         var command = new FastFourierTransformCommand(FTArray, FastFourierTransformCommandFlags.fastFourierTransform |  FastFourierTransformCommandFlags.gray);
         command.run(image);
         var rcRect = Leadtools.LeadRectHelper.create(0, 0, image.width / 2, image.height / 2);
         var FreqCommand = new FrequencyFilterCommand(FTArray, rcRect, FrequencyFilterCommandFlags.insideX | FrequencyFilterCommandFlags.outsideY);
         
         var InvCommand = new FastFourierTransformCommand(FTArray, FastFourierTransformCommandFlags.inverseFastFourierTransform |  FastFourierTransformCommandFlags.gray | FastFourierTransformCommandFlags.scale | FastFourierTransformCommandFlags.both);
         InvCommand.run(image);
      }
   });
}

[TestMethod]
public async Task FastFourierTransformCommandExample()
{
   // 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
   // Resize the image to make sure the image's dimensions are power of two.
   SizeCommand sizecommand = new SizeCommand(256, 256, Leadtools.RasterSizeFlags.Bicubic);

   sizecommand.Run(image);

   FourierTransformInformation FTArray = new FourierTransformInformation(image);
   // Apply FFT.
   FastFourierTransformCommand command = new FastFourierTransformCommand(FTArray, FastFourierTransformCommandFlags.FastFourierTransform |  FastFourierTransformCommandFlags.Gray);
   command.Run(image);
   LeadRect rcRect = LeadRectHelper.Create(0, 0, image.Width / 2, image.Height / 2);
   FrequencyFilterCommand FreqCommand = new FrequencyFilterCommand(FTArray, rcRect, FrequencyFilterCommandFlags.InsideX | FrequencyFilterCommandFlags.OutsideY);

   FastFourierTransformCommand InvCommand = new FastFourierTransformCommand(FTArray, FastFourierTransformCommandFlags.InverseFastFourierTransform |  FastFourierTransformCommandFlags.Gray | FastFourierTransformCommandFlags.Scale | FastFourierTransformCommandFlags.Both);
   InvCommand.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