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tompiler/.block

Last active May 30, 2017 13:10
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Adding text to Canvas
Raw
.block
license: mit
Raw
README.md
Raw
generate-prims.js
var N = 1 << 0,
S = 1 << 1,
W = 1 << 2,
E = 1 << 3;
self.addEventListener("message", function(event) {
postMessage(generateMaze(event.data.width, event.data.height));
});
function generateMaze(cellWidth, cellHeight) {
var cells = new Array(cellWidth * cellHeight),
frontier = minHeap(function(a, b) { return a.weight - b.weight; }),
startIndex = (cellHeight - 1) * cellWidth;
cells[startIndex] = 0;
frontier.push({index: startIndex, direction: N, weight: Math.random()});
frontier.push({index: startIndex, direction: E, weight: Math.random()});
while ((edge = frontier.pop()) != null) {
var edge,
i0 = edge.index,
d0 = edge.direction,
i1 = i0 + (d0 === N ? -cellWidth : d0 === S ? cellWidth : d0 === W ? -1 : +1),
x0 = i0 % cellWidth,
y0 = i0 / cellWidth | 0,
x1,
y1,
d1,
open = cells[i1] == null; // opposite not yet part of the maze
if (d0 === N) x1 = x0, y1 = y0 - 1, d1 = S;
else if (d0 === S) x1 = x0, y1 = y0 + 1, d1 = N;
else if (d0 === W) x1 = x0 - 1, y1 = y0, d1 = E;
else x1 = x0 + 1, y1 = y0, d1 = W;
if (open) {
cells[i0] |= d0, cells[i1] |= d1;
if (y1 > 0 && cells[i1 - cellWidth] == null) frontier.push({index: i1, direction: N, weight: Math.random()});
if (y1 < cellHeight - 1 && cells[i1 + cellWidth] == null) frontier.push({index: i1, direction: S, weight: Math.random()});
if (x1 > 0 && cells[i1 - 1] == null) frontier.push({index: i1, direction: W, weight: Math.random()});
if (x1 < cellWidth - 1 && cells[i1 + 1] == null) frontier.push({index: i1, direction: E, weight: Math.random()});
}
}
return cells;
}
function minHeap(compare) {
var heap = {},
array = [],
size = 0;
heap.empty = function() {
return !size;
};
heap.push = function(value) {
up(array[size] = value, size++);
return size;
};
heap.pop = function() {
if (size <= 0) return;
var removed = array[0], value;
if (--size > 0) value = array[size], down(array[0] = value, 0);
return removed;
};
function up(value, i) {
while (i > 0) {
var j = ((i + 1) >> 1) - 1,
parent = array[j];
if (compare(value, parent) >= 0) break;
array[i] = parent;
array[i = j] = value;
}
}
function down(value, i) {
while (true) {
var r = (i + 1) << 1,
l = r - 1,
j = i,
child = array[j];
if (l < size && compare(array[l], child) < 0) child = array[j = l];
if (r < size && compare(array[r], child) < 0) child = array[j = r];
if (j === i) break;
array[i] = child;
array[i = j] = value;
}
}
return heap;
}
Raw
index.html
<!DOCTYPE html>
<html>
<head>
<script src="https://d3js.org/d3.v4.min.js"></script>
</head>
<body>
<canvas id="canvas", width="1500" height="750"></canvas>
<script src="slide1.js" type="text/javascript"></script>
</body>
</html>
Raw
slide1.js
var canvas = d3.select("canvas"),
context = canvas.node().getContext("2d"),
width = canvas.property("width"),
height = canvas.property("height");
var worker = new Worker("generate-prims.js");
worker.postMessage({width: width, height: height});
worker.addEventListener("message", function(event) {
worker.terminate();
var N = 1 << 0,
S = 1 << 1,
W = 1 << 2,
E = 1 << 3;
var cells = event.data,
distance = 0,
visited = new Array(width * height),
frontier = [(height - 1) * width],
image = context.createImageData(width, height);
function flood() {
var frontier1 = [],
i0,
n0 = frontier.length,
i1,
color = d3.hsl((distance += .5) % 360, 0.5, .5).rgb();
for (var i = 0; i < n0; ++i) {
i0 = frontier[i] << 2;
image.data[i0 + 0] = color.r;
image.data[i0 + 1] = color.g;
image.data[i0 + 2] = color.b;
image.data[i0 + 3] = 255;
}
for (var i = 0; i < n0; ++i) {
i0 = frontier[i];
if (cells[i0] & E && !visited[i1 = i0 + 1]) visited[i1] = true, frontier1.push(i1);
if (cells[i0] & W && !visited[i1 = i0 - 1]) visited[i1] = true, frontier1.push(i1);
if (cells[i0] & S && !visited[i1 = i0 + width]) visited[i1] = true, frontier1.push(i1);
if (cells[i0] & N && !visited[i1 = i0 - width]) visited[i1] = true, frontier1.push(i1);
}
frontier = frontier1;
return !frontier1.length;
}
d3.timer(function() {
for (var i = 0, done; i < 3 && !(done = flood()); ++i);
context.putImageData(image, 0, 0);
context.font = 'bold 110px Arial, sans-serif';
context.fillStyle = '#ffffff';
context.fillText('Tech Lab:', 50, 320);
context.font = 'bold 90px Arial, sans-serif';
context.fillText('Interactive', 50, 420);
context.strokeStyle = 'black';
context.fillText('Data', 50, 500);
context.fillText('Visualisation', 50, 580);
context.fillText('with d3.js', 50, 650);
context.font = 'bold 70px Arial, sans-serif';
context.fillText('22nd March 2017', 800, 650);
context.textBaseline = 'bottom';
return done;
});
});
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