10,000 poisson-disc samples of Van Gogh’s The Starry Night. Compare to uniform random samples.
Last active
September 11, 2024 10:57
-
-
Save mbostock/22fd67be72552774736d to your computer and use it in GitHub Desktop.
Poisson-Disc III
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
license: gpl-3.0 |
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
<!DOCTYPE html> | |
<meta charset="utf-8"> | |
<body> | |
<script src="//d3js.org/d3.v3.min.js"></script> | |
<script> | |
var width = 960, | |
height = 500; | |
var sample = poissonDiscSampler(width, height, 5.45), | |
samples = [], | |
s; | |
while (s = sample()) samples.push(s); | |
var voronoi = d3.geom.voronoi() | |
.clipExtent([[0, 0], [width, height]]); | |
var canvas = d3.select("body").append("canvas") | |
.attr("width", width) | |
.attr("height", height); | |
var context = canvas.node().getContext("2d"); | |
var image = new Image; | |
image.src = "starry-night.jpg"; | |
image.onload = start; | |
function start() { | |
context.drawImage(image, 0, 0); | |
image = context.getImageData(0, 0, width, height); | |
voronoi(samples).forEach(function(cell) { | |
var x = Math.floor(cell.point[0]), | |
y = Math.floor(cell.point[1]), | |
i = (y * width + x) << 2; | |
context.fillStyle = d3.rgb(image.data[i + 0], image.data[i + 1], image.data[i + 2]) + ""; | |
context.beginPath(); | |
context.moveTo(cell[0][0], cell[0][1]); | |
for (var i = 1, n = cell.length; i < n; ++i) context.lineTo(cell[i][0], cell[i][1]); | |
context.closePath(); | |
context.fill(); | |
}); | |
} | |
// Based on https://www.jasondavies.com/poisson-disc/ | |
function poissonDiscSampler(width, height, radius) { | |
var k = 30, // maximum number of samples before rejection | |
radius2 = radius * radius, | |
R = 3 * radius2, | |
cellSize = radius * Math.SQRT1_2, | |
gridWidth = Math.ceil(width / cellSize), | |
gridHeight = Math.ceil(height / cellSize), | |
grid = new Array(gridWidth * gridHeight), | |
queue = [], | |
queueSize = 0, | |
sampleSize = 0; | |
return function() { | |
if (!sampleSize) return sample(Math.random() * width, Math.random() * height); | |
// Pick a random existing sample and remove it from the queue. | |
while (queueSize) { | |
var i = Math.random() * queueSize | 0, | |
s = queue[i]; | |
// Make a new candidate between [radius, 2 * radius] from the existing sample. | |
for (var j = 0; j < k; ++j) { | |
var a = 2 * Math.PI * Math.random(), | |
r = Math.sqrt(Math.random() * R + radius2), | |
x = s[0] + r * Math.cos(a), | |
y = s[1] + r * Math.sin(a); | |
// Reject candidates that are outside the allowed extent, | |
// or closer than 2 * radius to any existing sample. | |
if (0 <= x && x < width && 0 <= y && y < height && far(x, y)) return sample(x, y); | |
} | |
queue[i] = queue[--queueSize]; | |
queue.length = queueSize; | |
} | |
}; | |
function far(x, y) { | |
var i = x / cellSize | 0, | |
j = y / cellSize | 0, | |
i0 = Math.max(i - 2, 0), | |
j0 = Math.max(j - 2, 0), | |
i1 = Math.min(i + 3, gridWidth), | |
j1 = Math.min(j + 3, gridHeight); | |
for (j = j0; j < j1; ++j) { | |
var o = j * gridWidth; | |
for (i = i0; i < i1; ++i) { | |
if (s = grid[o + i]) { | |
var s, | |
dx = s[0] - x, | |
dy = s[1] - y; | |
if (dx * dx + dy * dy < radius2) return false; | |
} | |
} | |
} | |
return true; | |
} | |
function sample(x, y) { | |
var s = [x, y]; | |
queue.push(s); | |
grid[gridWidth * (y / cellSize | 0) + (x / cellSize | 0)] = s; | |
++sampleSize; | |
++queueSize; | |
return s; | |
} | |
} | |
</script> |
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment