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Discrete Fourier transformation
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| // Coding Challenge 130.3: Drawing with Fourier Transform and Epicycles | |
| // Daniel Shiffman | |
| // https://thecodingtrain.com/CodingChallenges/130.1-fourier-transform-drawing.html | |
| // https://thecodingtrain.com/CodingChallenges/130.2-fourier-transform-drawing.html | |
| // https://thecodingtrain.com/CodingChallenges/130.3-fourier-transform-drawing.html | |
| // https://youtu.be/7_vKzcgpfvU | |
| // https://editor.p5js.org/codingtrain/sketches/ldBlISrsQ | |
| class Complex { | |
| constructor(a, b) { | |
| this.re = a; | |
| this.im = b; | |
| } | |
| add(c) { | |
| this.re += c.re; | |
| this.im += c.im; | |
| } | |
| mult(c) { | |
| const re = this.re * c.re - this.im * c.im; | |
| const im = this.re * c.im + this.im * c.re; | |
| return new Complex(re, im); | |
| } | |
| } | |
| function dft(x) { | |
| const X = []; | |
| const N = x.length; | |
| for (let k = 0; k < N; k++) { | |
| let sum = new Complex(0, 0); | |
| for (let n = 0; n < N; n++) { | |
| const phi = (TWO_PI * k * n) / N; | |
| const c = new Complex(cos(phi), -sin(phi)); | |
| sum.add(x[n].mult(c)); | |
| } | |
| sum.re = sum.re / N; | |
| sum.im = sum.im / N; | |
| let freq = k; | |
| let amp = sqrt(sum.re * sum.re + sum.im * sum.im); | |
| let phase = atan2(sum.im, sum.re); | |
| X[k] = { re: sum.re, im: sum.im, freq, amp, phase }; | |
| } | |
| return X; | |
| } |
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| <!DOCTYPE html> | |
| <html> | |
| <head> | |
| <meta charset="UTF-8" /> | |
| <meta http-equiv="X-UA-Compatible" content="IE=edge" /> | |
| <meta name="viewport" content="width=device-width, initial-scale=1" /> | |
| <title>Discrete Fourier transformation</title> | |
| <script src="https://cdnjs.cloudflare.com/ajax/libs/p5.js/0.8.0/p5.min.js"></script> | |
| <script src="https://cdnjs.cloudflare.com/ajax/libs/p5.js/0.8.0/addons/p5.dom.min.js"></script> | |
| <script src="https://cdnjs.cloudflare.com/ajax/libs/raphael/2.2.8/raphael.min.js"></script> | |
| <script src="svg2vec.js"></script> | |
| <script src="fourier.js"></script> | |
| <script src="sketch.js"></script> | |
| </head> | |
| <body></body> | |
| </html> |
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| // Coding Challenge 130.3: Drawing with Fourier Transform and Epicycles | |
| // Daniel Shiffman | |
| // https://thecodingtrain.com/CodingChallenges/130.1-fourier-transform-drawing.html | |
| // https://thecodingtrain.com/CodingChallenges/130.2-fourier-transform-drawing.html | |
| // https://thecodingtrain.com/CodingChallenges/130.3-fourier-transform-drawing.html | |
| // https://youtu.be/7_vKzcgpfvU | |
| // https://editor.p5js.org/codingtrain/sketches/ldBlISrsQ | |
| let x = []; | |
| let fourierX; | |
| let time = 0; | |
| let path = []; | |
| let lengths = []; | |
| if (typeof(drawing) == 'undefined') | |
| var drawing = []; | |
| let w = 300; | |
| let h = 300; | |
| window.onhashchange = function() { | |
| x = []; | |
| time = 0; | |
| path = []; | |
| drawing = []; | |
| current_svg_xml = ''; | |
| setup(); | |
| }; | |
| function setup() { | |
| generatePointsFromSvg((window.location.hash ? window.location.hash.substr(1) : 'gh') + '.svg', (r) => { | |
| let scale = (w/r[1] < h/r[2]) ? w / (r[1] + 1) : h / (r[2] + 1); | |
| drawing = r[0].flat().map((e) => {return {x: e.x * scale, y: e.y * scale}}); | |
| lengths = []; // Do not allow large jumps | |
| for (let i = 1; i < drawing.length; i++) | |
| if (Math.sqrt(Math.pow(drawing[i].x - drawing[i-1].x, 2) + Math.pow(drawing[i].y - drawing[i-1].y, 2)) > 10) | |
| lengths.push(i); | |
| /*lengths = r[0].map((e) => e.length).slice(0, -1); | |
| for (let i = 1; i < lengths.length; i++) | |
| lengths[i] += lengths[i-1];*/ | |
| setup(); | |
| }); | |
| createCanvas(w, h); | |
| frameRate(60); | |
| const skip = 1; | |
| for (let i = 0; i < drawing.length; i += skip) { | |
| const c = new Complex(drawing[i].x, drawing[i].y); | |
| x.push(c); | |
| } | |
| fourierX = dft(x); | |
| fourierX.sort((a, b) => b.amp - a.amp); | |
| } | |
| function epicycles(x, y, rotation, fourier) { | |
| for (let i = 0; i < fourier.length; i++) { | |
| let prevx = x; | |
| let prevy = y; | |
| let freq = fourier[i].freq; | |
| let radius = fourier[i].amp; | |
| let phase = fourier[i].phase; | |
| x += radius * cos(freq * time + phase + rotation); | |
| y += radius * sin(freq * time + phase + rotation); | |
| stroke(255, 100); | |
| noFill(); | |
| ellipse(prevx, prevy, radius * 2); | |
| stroke(255); | |
| line(prevx, prevy, x, y); | |
| } | |
| return createVector(x, y); | |
| } | |
| function waves(fourierX) { | |
| /*if (fourierX.length < 1) return; | |
| let fourier = fourierX.slice(0, 10).sort((a, b) => a.freq - b.freq); | |
| let l = fourier.length; | |
| colorMode(HSB, l); | |
| for (let i = 0; i < l; i++) { | |
| beginShape(); | |
| for (let i2 = 0; i2 <= (time / TWO_PI) * width; i2++) { | |
| vertex(i2, height / 4 + fourier[i].amp + fourier[i].amp * sin(i2 / (TWO_PI * 4) + fourier[i].phase)); | |
| stroke(i, l, l); | |
| } | |
| endShape(); | |
| } | |
| colorMode(RGB, 255);*/ | |
| } | |
| function draw() { | |
| background(0); | |
| waves(fourierX); | |
| let v = epicycles(width / 2, height / 2, 0, fourierX); | |
| path.unshift(v); | |
| beginShape(); | |
| noFill(); | |
| for (let i = 0; i < path.length; i++) { | |
| if (lengths.includes(path.length - i)) { | |
| endShape(); | |
| beginShape(); | |
| } | |
| vertex(path[i].x, path[i].y); | |
| } | |
| endShape(); | |
| const dt = TWO_PI / fourierX.length; | |
| time += dt; | |
| if (time > TWO_PI) { | |
| time = 0; | |
| path = []; | |
| } | |
| } |
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| // Based on: https://github.com/Shinao/PathToPoints | |
| // To generate text: https://danmarshall.github.io/google-font-to-svg-path/ | |
| // Also consider: https://vecta.io/nano | |
| let current_svg_xml = ''; | |
| function generatePointsFromSvg(file, cb, step_point) { | |
| if (typeof(step_point) == 'undefined') step_point = 0.5; | |
| if (current_svg_xml == '') { | |
| let xhr = new XMLHttpRequest(); | |
| xhr.open('GET', file, true); | |
| xhr.onload = function(e) { | |
| current_svg_xml = this.response; | |
| cb(generatePointsFromSvg(file, cb, step_point)); | |
| }; | |
| xhr.send(); | |
| return; | |
| } | |
| let doc = (new DOMParser()).parseFromString(current_svg_xml, "application/xml"); | |
| let paths = doc.getElementsByTagName('path'); | |
| // Read each paths from svg | |
| let all_points = []; | |
| let bbox_path = doc.children[0].getAttribute('viewBox').split(' '); | |
| let width = parseFloat(bbox_path[2]), height = parseFloat(bbox_path[3]); | |
| for (let i = 0; i < paths.length; ++i) { | |
| let path = paths[i].getAttribute('d').replace(' ', ','); | |
| // get points at regular intervals | |
| let data_points = []; | |
| let c, l = Raphael.getTotalLength(path), step = step_point * Math.pow(Math.floor(Math.log(l) / Math.log(10)), 2); | |
| for (c = 0; c < l; c += step) { | |
| let point = Raphael.getPointAtLength(path, c); | |
| point.x = (point.x - (width / 2)); | |
| point.y = (point.y - (height / 2)); | |
| delete point.alpha; | |
| data_points.push(point); | |
| } | |
| all_points.push(data_points); | |
| } | |
| return [all_points, width, height]; | |
| } |
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