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130 | /*
BSD Zero Clause License
Permission to use, copy, modify, and/or distribute this software for any
purpose with or without fee is hereby granted.
THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH
REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT,
INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR
OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
PERFORMANCE OF THIS SOFTWARE.
*/
window.addEventListener('load', function () {
'use strict';
var canvas, ctx, reqAnimFrame;
canvas = document.getElementById("primeSpiralCanvas");
ctx = canvas.getContext("2d");
ctx.clearRect(0, 0, canvas.width, canvas.height);
reqAnimFrame =
window.requestAnimationFrame ||
window.webkitRequestAnimationFrame ||
window.mozRequestAnimationFrame ||
window.msRequestAnimationFrame ||
window.oRequestAnimationFrame ||
function (callback) {
return setTimeout(callback, 1);
};
var primes = [];
var curNum = 2;
var xInc = 0;
var yInc = 1;
var stepsTaken = 0;
var steps = 1;
var currentNum = 2;
var currentPoint = { x : Math.floor(canvas.width / 2),
y : Math.floor(canvas.height / 2) };
var getNextColour = function () {
var colours = ["red", "darkgray","blue"];
var i = colours.length - 1;
return function() {
i = (i + 1) % colours.length;
return colours[i];
};
}();
var curColour = getNextColour();
function resetVars() {
primes = [];
curNum = 2;
xInc = 0;
yInc = 1;
stepsTaken = 0;
steps = 1;
currentNum = 2;
currentPoint = { x : Math.floor(canvas.width / 2),
y : Math.floor(canvas.height / 2) };
}
function resizeCanvas() {
if (canvas.width != canvas.clientWidth ||
canvas.height != canvas.clientHeight) {
canvas.width = canvas.clientWidth;
canvas.height = canvas.clientHeight;
resetVars();
}
}
function nextPoint() {
if (stepsTaken >= steps) {
// rotate
var oldX = xInc;
xInc = yInc;
yInc = oldX;
xInc *= -1;
steps += 0.5;
stepsTaken = 0;
}
currentPoint.x += xInc;
currentPoint.y += yInc;
stepsTaken += 1;
}
function isPrime(myNum) {
var i;
for (i = 0; i < primes.length; i++) {
if(myNum % primes[i] === 0) {
return false;
}
}
primes.push(myNum);
return true;
}
function plotPoint() {
if (isPrime(currentNum)) {
ctx.fillRect(currentPoint.x, currentPoint.y, 1, 1);
}
nextPoint();
currentNum += 1;
}
function render() {
ctx.fillStyle = curColour;
resizeCanvas();
var i;
for (i = 0; i < steps / 2; i++) {
plotPoint();
}
// and again
if (currentPoint.x < 0 || currentPoint.x >= canvas.width
|| currentPoint.y < 0 || currentPoint.y >= canvas.height) {
// change colour
curColour = getNextColour();
resetVars();
}
reqAnimFrame(render);
}
render();
});
|