ComplexFft

Computes the Fast Fourier Transform of an image.

Access to parameter description

For an introduction: see section Frequency Domain.

This algorithm computes the FFT of an image. The result is two floating point images, respectively: the real and imaginary parts of the transform.

Remarks

To compute the module and phase of the FFT, the CartesianToPolar2d algorithm can be used.
The output images are centered in the upper left corner.
The SwapQuadrants algorithm can be used to move low frequencies in the image center.
The ComplexCenteredFft algorithm can be used to directly get a centered FFT.

See also

Function Syntax

This function returns a ComplexFftOutput structure containing the outputRealImage and outputImaginaryImage output parameters.

// Output structure.
struct ComplexFftOutput
{
    std::shared_ptr< iolink::ImageView > outputRealImage;
    std::shared_ptr< iolink::ImageView > outputImaginaryImage;
};

// Function prototype.
ComplexFftOutput
complexFft( std::shared_ptr< iolink::ImageView > inputImage,
            std::shared_ptr< iolink::ImageView > outputRealImage = NULL,
            std::shared_ptr< iolink::ImageView > outputImaginaryImage = NULL );

This function returns a tuple containing the output_real_image and output_imaginary_image output parameters.

// Function prototype.
complex_fft( input_image, output_real_image = None, output_imaginary_image = None )

This function returns a ComplexFftOutput structure containing the outputRealImage and outputImaginaryImage output parameters.

/// Output structure of the ComplexFft function.
public struct ComplexFftOutput
{
    public IOLink.ImageView outputRealImage;
    public IOLink.ImageView outputImaginaryImage;
};

// Function prototype.
public static ComplexFftOutput
ComplexFft( IOLink.ImageView inputImage,
            IOLink.ImageView outputRealImage = null,
            IOLink.ImageView outputImaginaryImage = null );

Class Syntax

Parameters

Class Name	ComplexFft

	Description	Type	Supported Values	Default Value
inputImage	The input image.	Image	Binary, Label, Grayscale or Multispectral	nullptr
outputRealImage	The output real part image. Its dimensions are forced to the same values as the input. Its data type is forced to floating point.	Image		nullptr
outputImaginaryImage	The output imaginary part image. Its dimensions are forced to the same values as the input. Its data type is forced to floating point.	Image		nullptr

Object Examples

auto polystyrene_float = readVipImage( std::string( IMAGEDEVDATA_IMAGES_FOLDER ) + "polystyrene_float.vip" );

ComplexFft complexFftAlgo;
complexFftAlgo.setInputImage( polystyrene_float );
complexFftAlgo.execute();

std::cout << "outputRealImage:" << complexFftAlgo.outputRealImage()->toString();
std::cout << "outputImaginaryImage:" << complexFftAlgo.outputImaginaryImage()->toString();

polystyrene_float = imagedev.read_vip_image(imagedev_data.get_image_path("polystyrene_float.vip"))

complex_fft_algo = imagedev.ComplexFft()
complex_fft_algo.input_image = polystyrene_float
complex_fft_algo.execute()

print( "output_real_image:", str( complex_fft_algo.output_real_image ) )
print( "output_imaginary_image:", str( complex_fft_algo.output_imaginary_image ) )

ImageView polystyrene_float = Data.ReadVipImage( @"Data/images/polystyrene_float.vip" );

ComplexFft complexFftAlgo = new ComplexFft
{
    inputImage = polystyrene_float
};
complexFftAlgo.Execute();

Console.WriteLine( "outputRealImage:" + complexFftAlgo.outputRealImage.ToString() );
Console.WriteLine( "outputImaginaryImage:" + complexFftAlgo.outputImaginaryImage.ToString() );

Function Examples

auto polystyrene_float = readVipImage( std::string( IMAGEDEVDATA_IMAGES_FOLDER ) + "polystyrene_float.vip" );

auto result = complexFft( polystyrene_float );

std::cout << "outputRealImage:" << result.outputRealImage->toString();
std::cout << "outputImaginaryImage:" << result.outputImaginaryImage->toString();

polystyrene_float = imagedev.read_vip_image(imagedev_data.get_image_path("polystyrene_float.vip"))

result_output_real_image, result_output_imaginary_image = imagedev.complex_fft( polystyrene_float )

print( "output_real_image:", str( result_output_real_image ) )
print( "output_imaginary_image:", str( result_output_imaginary_image ) )

ImageView polystyrene_float = Data.ReadVipImage( @"Data/images/polystyrene_float.vip" );

Processing.ComplexFftOutput result = Processing.ComplexFft( polystyrene_float );

Console.WriteLine( "outputRealImage:" + result.outputRealImage.ToString() );
Console.WriteLine( "outputImaginaryImage:" + result.outputImaginaryImage.ToString() );