dft | 易学教程

洛谷P5158 【模板】多项式快速插值

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https://www.luogu.org/problemnew/show/P5158 题解： https://www.cnblogs.com/zzqsblog/p/7923192.html 备份版本1：基于版本1 1 #prag\ 2 ma GCC optimize(2) 3 #include<cstdio> 4 #include<algorithm> 5 #include<cstring> 6 #include<vector> 7 #include<cmath> 8 using namespace std; 9 #define fi first 10 #define se second 11 #define mp make_pair 12 #define pb push_back 13 typedef long long ll; 14 typedef unsigned long long ull; 15 const int md=998244353; 16 const int N=262144; 17 #define delto(a,b) ((a)-=(b),((a)<0)&&((a)+=md)) 18 inline int del(int a,int b) 19 { 20 a-=b; 21 return a<0?a+md:a; 22 } 23 int rev[N]; 24

Inverse fourier transformation in OpenCV

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问题 I am new in OpenCV and image processing algorithms. I need to do inverse discrete fourier transformation in OpenCV in C++, but I don't know how. I searched over internet and I didn't find answer. I am doing fourier transformation in my program with this code from this page: http://opencv.itseez.com/doc/tutorials/core/discrete_fourier_transform/discrete_fourier_transform.html. I have tried to do inverse to that code, but I don't know where I am doing wrong. My code is here (I think that whole

Convert OpenCv DFT example from C++ to Android

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问题 I want to implement follwoing OpenCV example in a Android app: http://docs.opencv.org/doc/tutorials/core/discrete_fourier_transform/discrete_fourier_transform.html My code is the foll0wing: //First convert Bitmap to Mat Mat ImageMat = new Mat ( image.getHeight(), image.getWidth(), CvType.CV_64FC1, new Scalar(4)); Bitmap myBitmap32 = image.copy(Bitmap.Config.ARGB_8888, true); Utils.bitmapToMat(myBitmap32, ImageMat); Imgproc.cvtColor(ImageMat, ImageMat, Imgproc.COLOR_RGB2GRAY); Mat padded = new

Verify the convolution theorem

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问题 My main goal is to show that the convolution theorem works (just a reminder: the convolution theorem means that idft(dft(im) .* dft(mask)) = conv(im, mask) ). I'm trying to program that. Here is my code: function displayTransform( im ) % This routine displays the Fourier spectrum of an image. % % Input: im - a grayscale image (values in [0,255]) % % Method: Computes the Fourier transform of im and displays its spectrum, % (if F(u,v) = a+ib, displays sqrt(a^2+b^2)). % Uses display techniques

How to compute Discrete Fourier Transform?

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I've been trying to find some places to help me better understand DFT and how to compute it but to no avail. So I need help understanding DFT and it's computation of complex numbers. Basically, I'm just looking for examples on how to compute DFT with an explanation on how it was computed because in the end, I'm looking to create an algorithm to compute it. I assume 1D DFT/IDFT ... All DFT's use this formula: X(k) is transformed sample value (complex domain) x(n) is input data sample value (real or complex domain) N is number of samples/values in your dataset This whole thing is usually

How to compute Discrete Fourier Transform?

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问题 I\'ve been trying to find some places to help me better understand DFT and how to compute it but to no avail. So I need help understanding DFT and it\'s computation of complex numbers. Basically, I\'m just looking for examples on how to compute DFT with an explanation on how it was computed because in the end, I\'m looking to create an algorithm to compute it. 回答1: I assume 1D DFT/IDFT ... All DFT's use this formula: X(k) is transformed sample value (complex domain) x(n) is input data sample