View source: R/template_matching.R
convFFT | R Documentation |
Convolve a three-dimensinal array with another three-dimensional arry using the Fast Fourier Transform (FFT).
convFFT(A, B, C, FFTA = NULL)
A |
is a three-dimensional array (“the template”). |
B |
is a three-dimensional array (“the target”). |
C |
is a vector of length three (the center of “the template”). |
FFTA |
is the three-dimensional Fourier transform of |
The arrays A and B are transformed into the Fourier domain and multiplied together (equivalent to a convolution in the image domain across all spatial locations simultaneously).
A three-dimensional array, the same dimension as the input arrays, that is the convolution of the “target” to the “template” at all spatial locations.
Brandon Whitcher bwhitcher@gmail.com
Briggs, W.L. and Henson, V.E. (1995) The DFT: An Owner's Manual for the Discrete Fourier Transform, SIAM: Philadelphia.
fft
, fastTemplateMatching
, shift3D
cube <- array(0, c(20,20,1)) cube[9:12,9:12,1] <- 1 tkernel <- array(0, c(20,20,1)) tkernel[,,1] <- c(.5, 1, .5, rep(0,20-3)) %o% c(.5, 1, .5, rep(0,20-3)) tcenter <- findCenter(ifelse(tkernel > 0, TRUE, FALSE)) out <- convFFT(tkernel, cube, tcenter) out[8:13,8:13,1] ## text output par(mfrow=c(2,2)) ## graphic output image(drop(tkernel), col=oro.nifti::tim.colors(), main="Template") image(drop(cube), col=oro.nifti::tim.colors(), main="Target") image(drop(out), col=oro.nifti::tim.colors(), main="Output")
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