How do I make this HTML5 script canvas full screen?
I am having trouble trying to set the canvas to fill the entire window. It is currently set at 500x500. I am new to coding and would greatly appreciate any help! Thank.
Here is the code:
<!DOCTYPE html>
<html>
<head>
<title>Starfield effect done in HTML 5</title>
<script>
window.onload = function() {
/* --- config start --- */
var starfieldCanvasId = "starfieldCanvas", // id of the canvas to use
framerate = 60, // frames per second this animation runs at (this is not exact)
numberOfStarsModifier = 0.15, // Number of stars, higher numbers have performance impact
flightSpeed = 0.003; // speed of the flight, the higher this number the faster
/* ---- config end ---- */
var canvas = document.getElementById(starfieldCanvasId),
context = canvas.getContext("2d"),
width = canvas.width,
height = canvas.height,
numberOfStars = width * height / 1000 * numberOfStarsModifier,
dirX = width / 2,
dirY = height / 2,
stars = [],
TWO_PI = Math.PI * 2;
// initialize starfield
for(var x = 0; x < numberOfStars; x++) {
stars[x] = {
x: range(0, width),
y: range(0, height),
size: range(0, 1)
};
}
// when mouse moves over canvas change middle point of animation
canvas.onmousemove = function(event) {
dirX = event.offsetX,
dirY = event.offsetY;
}
// start tick at specified fps
window.setInterval(tick, Math.floor(1000 / framerate));
// main routine
function tick() {
var oldX,
oldY;
// reset canvas for next frame
context.clearRect(0, 0, width, height);
for(var x = 0; x < numberOfStars; x++) {
// save old status
oldX = stars[x].x;
oldY = stars[x].y;
// calculate changes to star
stars[x].x += (stars[x].x - dirX) * stars[x].size * flightSpeed;
stars[x].y += (stars[x].y - dirY) * stars[x].size * flightSpeed;
stars[x].size += flightSpeed;
// if star is out of bounds, reset
if(stars[x].x < 0 || stars[x].x > width || stars[x].y < 0 || stars[x].y > height) {
stars[x] = {
x: range(0, width),
y: range(0, height),
size: 0
};
}
// draw star
context.strokeStyle = "rgba(255, 255, 255, " + Math.min(stars[x].size, 1) + ")";
context.lineWidth = stars[x].size;
context.beginPath();
context.moveTo(oldX, oldY);
context.lineTo(stars[x].x, stars[x].y);
context.stroke();
}
}
// get a random number inside a range
function range(start, end) {
return Math.random() * (end - start) + start;
}
};
</script>
</head>
<body style="background:#000;">
<canvas width="500" height="500" id="starfieldCanvas"></canvas>
</body>
</html>
Original code and credit: https://www.timewasters-place.com/starfield-animation-done-in-html-5/
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1 answer
I assume you want your script to auto-detect the screen size and then to set the canvas to full screen instead of a 500 x 500 hard drive currently.
You can determine the size of the viewport programmatically using the following, where the width and height correspond respectively. (Source) :
var width = window.innerWidth
|| document.documentElement.clientWidth
|| document.body.clientWidth;
var height = window.innerHeight
|| document.documentElement.clientHeight
|| document.body.clientHeight;
Then you can set the dimensions of your canvas like this:
canvas.width = width;
canvas.height = height;
So this would be the complete code in your case:
<!DOCTYPE html>
<html>
<head>
<title>Starfield effect done in HTML 5</title>
<script>
window.onload = function() {
/* --- config start --- */
var starfieldCanvasId = "starfieldCanvas", // id of the canvas to use
framerate = 60, // frames per second this animation runs at (this is not exact)
numberOfStarsModifier = 0.15, // Number of stars, higher numbers have performance impact
flightSpeed = 0.003; // speed of the flight, the higher this number the faster
var width = window.innerWidth
|| document.documentElement.clientWidth
|| document.body.clientWidth;
var height = window.innerHeight
|| document.documentElement.clientHeight
|| document.body.clientHeight;
/* ---- config end ---- */
var canvas = document.getElementById(starfieldCanvasId),
context = canvas.getContext("2d"),
stars = [],
TWO_PI = Math.PI * 2;
canvas.width = width;
canvas.height = height;
numberOfStars = width * height / 1000 * numberOfStarsModifier;
dirX = width / 2;
dirY = height / 2;
// initialize starfield
for(var x = 0; x < numberOfStars; x++) {
stars[x] = {
x: range(0, width),
y: range(0, height),
size: range(0, 1)
};
}
// when mouse moves over canvas change middle point of animation
canvas.onmousemove = function(event) {
dirX = event.offsetX,
dirY = event.offsetY;
}
// start tick at specified fps
window.setInterval(tick, Math.floor(1000 / framerate));
// main routine
function tick() {
var oldX,
oldY;
// reset canvas for next frame
context.clearRect(0, 0, width, height);
for(var x = 0; x < numberOfStars; x++) {
// save old status
oldX = stars[x].x;
oldY = stars[x].y;
// calculate changes to star
stars[x].x += (stars[x].x - dirX) * stars[x].size * flightSpeed;
stars[x].y += (stars[x].y - dirY) * stars[x].size * flightSpeed;
stars[x].size += flightSpeed;
// if star is out of bounds, reset
if(stars[x].x < 0 || stars[x].x > width || stars[x].y < 0 || stars[x].y > height) {
stars[x] = {
x: range(0, width),
y: range(0, height),
size: 0
};
}
// draw star
context.strokeStyle = "rgba(255, 255, 255, " + Math.min(stars[x].size, 1) + ")";
context.lineWidth = stars[x].size;
context.beginPath();
context.moveTo(oldX, oldY);
context.lineTo(stars[x].x, stars[x].y);
context.stroke();
}
}
// get a random number inside a range
function range(start, end) {
return Math.random() * (end - start) + start;
}
};
</script>
</head>
<body style="background:#000;">
<canvas id="starfieldCanvas"></canvas>
</body>
</html>
I have also checked this on Fiddle. Here's the link: Fiddle
Hope this helps! Let me know if it works.
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