How to make this HTML5 canvas script to full screen?

Question

I am having trouble trying to set the canvas to fill the whole window. It is currently set to 500x500.. I am new to coding and would really appreciate any help! Thank you.

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 to: https://www.timewasters-place.com/starfield-animation-done-in-html-5/

Answer 1

I assume you mean that you want your script to determine the screen size automatically, and then to set the canvas to be the full screen instead of the hardcoded 500 x 500 currently.

You can determine the viewport size programatically using the following where the width and height are as follows 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 as follows:

canvas.width  = width;
canvas.height = height;

So, this would be the full 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 also tested this on Fiddle. Here's the link: Fiddle

Hope this helps! Let me know if it works.

How to make this HTML5 canvas script to full screen?

Question

1 answers

solution1
1 ACCPTED 2017-04-01 23:19:48

How to make this HTML5 canvas script to full screen?

Question

1 answers

solution1 1 ACCPTED 2017-04-01 23:19:48

solution1
1 ACCPTED 2017-04-01 23:19:48