Operator Reference

phase_correlation_fftphase_correlation_fftPhaseCorrelationFftPhaseCorrelationFftphase_correlation_fft (Operator)

phase_correlation_fftphase_correlation_fftPhaseCorrelationFftPhaseCorrelationFftphase_correlation_fft — Compute the phase correlation of two images in the frequency domain.

Signature

phase_correlation_fft(ImageFFT1, ImageFFT2 : ImagePhaseCorrelation : : )

Description

phase_correlation_fftphase_correlation_fftPhaseCorrelationFftPhaseCorrelationFftphase_correlation_fft calculates the phase correlation of the Fourier-transformed input images in the frequency domain. The phase correlation is calculated by multiplying ImageFFT1ImageFFT1ImageFFT1imageFFT1image_fft1 with the complex conjugate of ImageFFT2ImageFFT2ImageFFT2imageFFT2image_fft2 and dividing by the absolute value of this product. It should be noted that in order to achieve a correct scaling of the phase correlation in the spatial domain, the operators fft_genericfft_genericFftGenericFftGenericfft_generic or rft_genericrft_genericRftGenericRftGenericrft_generic with NormNormNormnormnorm = 'none'"none""none""none""none" must be used for the forward transform and fft_genericfft_genericFftGenericFftGenericfft_generic or rft_genericrft_genericRftGenericRftGenericrft_generic with NormNormNormnormnorm = 'n'"n""n""n""n" for the reverse transform. If ImageFFT1ImageFFT1ImageFFT1imageFFT1image_fft1 and ImageFFT2ImageFFT2ImageFFT2imageFFT2image_fft2 contain the same number of images, the corresponding images are phase-correlated pairwise. Otherwise, ImageFFT2ImageFFT2ImageFFT2imageFFT2image_fft2 must contain only one single image. In this case, the phase correlation is performed for each image of ImageFFT1ImageFFT1ImageFFT1imageFFT1image_fft1 with ImageFFT2ImageFFT2ImageFFT2imageFFT2image_fft2 .

Attention

The filtering is always performed on the entire image, i.e., the domain of the image is ignored.

Execution Information

Multithreading type: reentrant (runs in parallel with non-exclusive operators).
Multithreading scope: global (may be called from any thread).
Automatically parallelized on tuple level.
Automatically parallelized on channel level.

Parameters

ImageFFT1ImageFFT1ImageFFT1imageFFT1image_fft1 (input_object) (multichannel-)image(-array) → object (complex)

Fourier-transformed input image 1.

ImageFFT2ImageFFT2ImageFFT2imageFFT2image_fft2 (input_object) (multichannel-)image(-array) → object (complex)

Fourier-transformed input image 2.

Number of elements: ImageFFT2 == ImageFFT1 || ImageFFT2 == 1

ImagePhaseCorrelationImagePhaseCorrelationImagePhaseCorrelationimagePhaseCorrelationimage_phase_correlation (output_object) image(-array) → object (complex)

Phase correlation of the input images in the frequency domain.

Example (HDevelop)

* Compute the phase correlation of two images.
get_image_size(Image1,Width,Height)
rft_generic(Image1,ImageFFT1,'to_freq','none','complex',Width)
rft_generic(Image2,ImageFFT2,'to_freq','none','complex',Width)
phase_correlation_fft(ImageFFT1,ImageFFT2,PhaseCorrelationFFT)
rft_generic(PhaseCorrelationFFT,PhaseCorrelation,'from_freq','n', \
            'real',Width)
* Determine the translation between the two images.
local_max_sub_pix (PhaseCorrelation, 'facet', 1, 0.02, Row, Column)

Result

phase_correlation_fftphase_correlation_fftPhaseCorrelationFftPhaseCorrelationFftphase_correlation_fft returns 2 ( H_MSG_TRUE) if all parameters are correct. If the input is empty the behavior can be set via set_system(::'no_object_result',<Result>:)set_system("no_object_result",<Result>)SetSystem("no_object_result",<Result>)SetSystem("no_object_result",<Result>)set_system("no_object_result",<Result>). If necessary, an exception is raised.

Possible Predecessors

fft_genericfft_genericFftGenericFftGenericfft_generic, fft_imagefft_imageFftImageFftImagefft_image, rft_genericrft_genericRftGenericRftGenericrft_generic

Possible Successors

fft_genericfft_genericFftGenericFftGenericfft_generic, fft_image_invfft_image_invFftImageInvFftImageInvfft_image_inv, rft_genericrft_genericRftGenericRftGenericrft_generic

Alternatives

correlation_fftcorrelation_fftCorrelationFftCorrelationFftcorrelation_fft

References

C. D. Kuglin, D. C. Hines: “The Phase Correlation Image Alignment Method”; IEEE International Conference on Cybernetics and Society; pp. 163-165; 1975.

Module

Foundation

Operators