kissfft

FFTW fftwf_plan_r2r_2d() with FFTW_REDFT01 equivalent

由 别来无恙 提交于 2019-12-08 11:52:29
问题 I am trying to port code that uses FFTW to use KissFFT. The code uses fftwf_plan_r2r_2d() with FFTW_REDFT01. What would be the equivalent call in KissFFT? If this call (with FFTW_REDFT01 ) is equivalent to a DCT, could I just use a direct DCT transform instead, e.g. such as OpenCV cv::dct? Is there some input data modification I'd need to do, like reflections and symmetrizations? 回答1: Answering my own question... With the help of these two references, I ended up not using DFT at all, but

How to perform FFT2D (Fast Fourier Transform 2D) R, G, B color component

由 …衆ロ難τιáo~ 提交于 2019-12-06 04:23:37
问题 I am new in fast fourier transform (FFT) and does not have much idea, how it calculate in programming language such as C++. Here is method of FFT2D void FFT2D(Complex<double> *f, Complex<double> *F, int width, int height); It takes an input image f of size width * height and output the transformed coefficients into F. Hints: Image pixels are stored as three separate image color (R, G, B) planes, with each of them being represented by a 1D array of complex numbers. Suppose an image is of size

Gaussian Blur with FFT Questions

由 回眸只為那壹抹淺笑 提交于 2019-12-04 13:08:04
问题 I have a current implementation of Gaussian Blur using regular convolution. It is efficient enough for small kernels, but once the kernels size gets a little bigger, the performance takes a hit. So, I am thinking to implement the convolution using FFT. I've never had any experience with FFT related image processing so I have a few questions. Is a 2D FFT based convolution also separable into two 1D convolutions ? If true, does it go like this - 1D FFT on every row, and then 1D FFT on every

How to perform FFT2D (Fast Fourier Transform 2D) R, G, B color component

由 随声附和 提交于 2019-12-04 10:51:30
I am new in fast fourier transform (FFT) and does not have much idea, how it calculate in programming language such as C++. Here is method of FFT2D void FFT2D(Complex<double> *f, Complex<double> *F, int width, int height); It takes an input image f of size width * height and output the transformed coefficients into F. Hints: Image pixels are stored as three separate image color (R, G, B) planes, with each of them being represented by a 1D array of complex numbers. Suppose an image is of size width W and height H, then the color component values (R, G and B) of the pixels at image location (m,

Gaussian Blur with FFT Questions

由 这一生的挚爱 提交于 2019-12-03 08:49:44
I have a current implementation of Gaussian Blur using regular convolution. It is efficient enough for small kernels, but once the kernels size gets a little bigger, the performance takes a hit. So, I am thinking to implement the convolution using FFT. I've never had any experience with FFT related image processing so I have a few questions. Is a 2D FFT based convolution also separable into two 1D convolutions ? If true, does it go like this - 1D FFT on every row, and then 1D FFT on every column, then multiply with the 2D kernel and then inverse transform of every column and the inverse

Not getting the exact data when reversing FFT

由 喜夏-厌秋 提交于 2019-12-02 16:57:15
问题 Okay, what I'm trying to achieve is simple. Apply FFT on some random data and then apply the reverse algorithm on the output to get back the input. I'm using kissFFT library for this. Code: const int fft_siz = 512; const int inverse = 1; kiss_fft_cpx* in = (kiss_fft_cpx*)malloc(sizeof(kiss_fft_cpx) * fft_siz); kiss_fft_cpx* out = (kiss_fft_cpx*)malloc(sizeof(kiss_fft_cpx) * fft_siz); kiss_fft_cpx* rec = (kiss_fft_cpx*)malloc(sizeof(kiss_fft_cpx) * fft_siz); kiss_fft_cfg cfg = kiss_fft_alloc

Not getting the exact data when reversing FFT

由 我是研究僧i 提交于 2019-12-02 12:30:27
Okay, what I'm trying to achieve is simple. Apply FFT on some random data and then apply the reverse algorithm on the output to get back the input. I'm using kissFFT library for this. Code: const int fft_siz = 512; const int inverse = 1; kiss_fft_cpx* in = (kiss_fft_cpx*)malloc(sizeof(kiss_fft_cpx) * fft_siz); kiss_fft_cpx* out = (kiss_fft_cpx*)malloc(sizeof(kiss_fft_cpx) * fft_siz); kiss_fft_cpx* rec = (kiss_fft_cpx*)malloc(sizeof(kiss_fft_cpx) * fft_siz); kiss_fft_cfg cfg = kiss_fft_alloc(fft_siz, !inverse, NULL, NULL); kiss_fft_cfg icfg = kiss_fft_alloc(fft_siz, inverse, NULL, NULL); srand(

kissfft scaling

由 删除回忆录丶 提交于 2019-11-29 03:12:36
问题 I am looking to compute a fast correlation using FFTs and the kissfft library, and scaling needs to be precise. What scaling is necessary (forward and backwards) and what value do I use to scale my data? 回答1: The 3 most common FFT scaling factors are: 1.0 forward FFT, 1.0/N inverse FFT 1.0/N forward FFT, 1.0 inverse FFT 1.0/sqrt(N) in both directions, FFT & IFFT Given any possible ambiguity in the documentation, and for whatever scaling the user expects to be "correct" for their purposes,
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