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Double image background on canvas not sharing the same size

I'm trying to make a section on a website have two background images that will reveal the bottom one as the pointer moves across the screen.
I'm still new to javascript, and my code is made up of bits and pieces that I've found on google, but I can't seem to get the top image to share the same resolution and image size for whatever reason as the bottom image.
Here is the link to my codepen: https://codepen.io/Awktopus/pen/zYwKOKO
And here is my code:
HTML:
<canvas id="main-canvas" id="canvas-size" class="background-size"></canvas>
<image src="https://i.imgur.com/PbGAAIy.jpg" id="upper-image" class="hidden-bg"></img>
<image src="https://i.imgur.com/Gx14sKW.jpg" id="lower-image" class="hidden-bg"></img>
CSS:
.hidden-bg {
display: none;
}
JS:
var can = document.getElementById('main-canvas');
var ctx = can.getContext('2d');
can.width = window.innerWidth;
can.height = window.innerWidth / 2;
var upperImg = document.getElementById("upper-image");
var lowerImg = document.getElementById("lower-image");
var pat = ctx.createPattern(upperImg, "no-repeat");
var canvas = ctx.canvas ;
var hRatio = canvas.width / lowerImg.width ;
var vRatio = canvas.height / lowerImg.height ;
var ratio = Math.max ( hRatio, vRatio );
var centerShift_x = ( canvas.width - lowerImg.width*ratio ) / 2;
var centerShift_y = ( canvas.height - lowerImg.height*ratio ) / 2;
can.addEventListener('mousemove', function(e) {
var mouse = getMouse(e, can);
redraw(mouse);
}, false);
function redraw(mouse) {
can.width = can.width;
ctx.clearRect(0,0,canvas.width, canvas.height);
ctx.drawImage(lowerImg, 0,0, lowerImg.width, lowerImg.height, centerShift_x,centerShift_y,lowerImg.width*ratio, lowerImg.height*ratio);
ctx.beginPath();
ctx.rect(0,0,can.width,can.height);
ctx.arc(mouse.x, mouse.y, 250, 0, Math.PI*2, true)
ctx.clip();
ctx.fillStyle = pat;
ctx.fillRect(0, 0, lowerImg.width, lowerImg.height, centerShift_x, centerShift_y, lowerImg.width*ratio, lowerImg.height*ratio);
}
var img = new Image();
img.onload = function() {
redraw({x: -500, y:-500})
}
function getMouse(e, canvas) {
var element = canvas,
offsetX = 0,
offsetY = 0,
mx, my;
if (element.offsetParent !== undefined) {
do {
offsetX += element.offsetLeft;
offsetY += element.offsetTop;
} while ((element = element.offsetParent));
}
mx = e.pageX - offsetX;
my = e.pageY - offsetY;
return {
x: mx,
y: my
};
}

If I understood this right you will want to set the width and height and draw the upper image using drawImage(). Just use the same ratios as the lowerImage. No need to use createPattern for this.
codepen: https://codepen.io/jfirestorm44/pen/BaRLoxX
var can = document.getElementById('main-canvas');
var ctx = can.getContext('2d');
can.width = window.innerWidth;
can.height = window.innerWidth / 2;
var upperImg = document.getElementById("upper-image");
var lowerImg = document.getElementById("lower-image");
//var pat = ctx.createPattern(upperImg, "no-repeat");
var canvas = ctx.canvas ;
var hRatio = canvas.width / lowerImg.width ;
var vRatio = canvas.height / lowerImg.height ;
var ratio = Math.max ( hRatio, vRatio );
var centerShift_x = ( canvas.width - lowerImg.width*ratio ) / 2;
var centerShift_y = ( canvas.height - lowerImg.height*ratio ) / 2;
can.addEventListener('mousemove', function(e) {
var mouse = getMouse(e, can);
redraw(mouse);
}, false);
function redraw(mouse) {
can.width = can.width;
ctx.clearRect(0,0,canvas.width, canvas.height);
ctx.drawImage(lowerImg, 0,0, lowerImg.width, lowerImg.height, centerShift_x,centerShift_y,lowerImg.width*ratio, lowerImg.height*ratio);
ctx.beginPath();
ctx.rect(0,0,can.width,can.height);
ctx.arc(mouse.x, mouse.y, 250, 0, Math.PI*2, true)
ctx.clip();
ctx.drawImage(upperImg, 0,0, lowerImg.width, lowerImg.height, centerShift_x,centerShift_y,lowerImg.width*ratio, lowerImg.height*ratio);
}
var img = new Image();
img.onload = function() {
redraw({x: -500, y:-500})
}
function getMouse(e, canvas) {
var element = canvas,
offsetX = 0,
offsetY = 0,
mx, my;
if (element.offsetParent !== undefined) {
do {
offsetX += element.offsetLeft;
offsetY += element.offsetTop;
} while ((element = element.offsetParent));
}
mx = e.pageX - offsetX;
my = e.pageY - offsetY;
return {
x: mx,
y: my
};
}
.hidden-bg {
display: none;
}
<canvas id="main-canvas" id="canvas-size" class="background-size"></canvas>
<image src="https://i.imgur.com/PbGAAIy.jpg" id="upper-image" class="hidden-bg"></img>
<image src="https://i.imgur.com/Gx14sKW.jpg" id="lower-image" class="hidden-bg"></img>

How to create fading cursor trails on an image canvas?

I've created a cursor trail over an image canvas where the image canvas is at the background and the cursor trail is on a second canvas on top of the image canvas. The issue I'm currently facing is that I am unable to create a trail that fades away gradually.
I've seen tips on how to make it fade with a plain background using fillStyle but I don't know how to make a fading cursor trail work with an image as the background.
<!DOCTYPE html>
<html>
<head>
<style>
.stack {
position: relative;
}
.stack canvas {
position: absolute;
left: 0;
top: 0;
}
.stack,
#main_canvas {
background-size: contain;
width: 100%;
margin: auto;
}
</style>
</head>
<body>
<div class="stack">
<canvas id="main_canvas"> main canvas</canvas>
</div>
<script>
var SCREEN_WIDTH = window.innerWidth;
var SCREEN_HEIGHT = window.innerHeight;
var RADIUS = 70;
var RADIUS_SCALE = 1;
var RADIUS_SCALE_MIN = 1;
var RADIUS_SCALE_MAX = 1.5;
var QUANTITY = 25;
var canvas;
var canvas_bg;
var context;
var context_bg;
var particles;
var slider_image;
var mouseX = SCREEN_WIDTH * 0.5;
var mouseY = SCREEN_HEIGHT * 0.5;
var mouseIsDown = false;
var ind = 0;
function init() {
canvas = document.getElementById("main_canvas");
canvas_bg = document.createElement("canvas"); //<canvas> predefined
canvas.setAttribute("alt", "countless stars");
if (canvas && canvas.getContext) {
windowResizeHandler();
//background canvas
create_sliders();
//main canvas for creating mouse trails
context = canvas.getContext("2d");
// Register event listeners
window.addEventListener("mousemove", documentMouseMoveHandler, false);
window.addEventListener("mousedown", documentMouseDownHandler, false);
window.addEventListener("mouseup", documentMouseUpHandler, false);
document.addEventListener(
"touchstart",
documentTouchStartHandler,
false
);
document.addEventListener(
"touchmove",
documentTouchMoveHandler,
false
);
window.addEventListener("resize", windowResizeHandler, false);
createParticles();
setInterval(loop, 1000 / 60);
}
}
function create_sliders() {
slider_image = new Image();
slider_image.src =
"https://images.pexels.com/photos/956999/milky-way-starry-sky-night-sky-star-956999.jpeg?auto=compress&cs=tinysrgb&dpr=2&h=650&w=940";
canvas_bg.width = canvas.width;
canvas_bg.height = canvas.height;
// insert into DOM on top:
canvas.parentNode.insertBefore(canvas_bg, canvas);
context_bg = canvas_bg.getContext("2d");
context_bg.drawImage(slider_image, 0, 0, canvas.width, canvas.height);
}
function createParticles() {
particles = [];
for (var i = 0; i < QUANTITY; i++) {
var particle = {
size: 1,
position: { x: mouseX, y: mouseY },
offset: { x: 0, y: 0 },
shift: { x: mouseX, y: mouseY },
speed: 0.01 + Math.random() * 0.04,
targetSize: 1,
fillColor:
"#" + ((Math.random() * 0x404040 + 0xaaaaaa) | 0).toString(16),
orbit: RADIUS * 0.5 + RADIUS * 0.5 * Math.random()
};
particles.push(particle);
}
}
function documentMouseMoveHandler(event) {
mouseX = event.clientX - (window.innerWidth - SCREEN_WIDTH) * 0.5;
mouseY = event.clientY - (window.innerHeight - SCREEN_HEIGHT) * 0.5;
}
function documentMouseDownHandler(event) {
mouseIsDown = true;
}
function documentMouseUpHandler(event) {
mouseIsDown = false;
}
function documentTouchStartHandler(event) {
if (event.touches.length == 1) {
event.preventDefault();
mouseX =
event.touches[0].pageX - (window.innerWidth - SCREEN_WIDTH) * 0.5;
mouseY =
event.touches[0].pageY - (window.innerHeight - SCREEN_HEIGHT) * 0.5;
}
}
function documentTouchMoveHandler(event) {
if (event.touches.length == 1) {
event.preventDefault();
mouseX =
event.touches[0].pageX - (window.innerWidth - SCREEN_WIDTH) * 0.5;
mouseY =
event.touches[0].pageY - (window.innerHeight - SCREEN_HEIGHT) * 0.5;
}
}
function windowResizeHandler() {
SCREEN_WIDTH = window.innerWidth;
SCREEN_HEIGHT = window.innerHeight;
canvas.width = SCREEN_WIDTH;
canvas.height = SCREEN_HEIGHT;
}
function loop() {
if (mouseIsDown) {
RADIUS_SCALE += (RADIUS_SCALE_MAX - RADIUS_SCALE) * 0.02;
} else {
RADIUS_SCALE -= (RADIUS_SCALE - RADIUS_SCALE_MIN) * 0.02;
}
RADIUS_SCALE = Math.min(RADIUS_SCALE, RADIUS_SCALE_MAX);
// context.fillStyle = 'rgba(0,0,0,0.05)';
context.fillStyle = "rgba(0, 0, 0, 0)";
context.fillRect(0, 0, context.canvas.width, context.canvas.height);
for (i = 0, len = particles.length; i < len; i++) {
var particle = particles[i];
var lp = { x: particle.position.x, y: particle.position.y };
// Rotation
particle.offset.x += particle.speed;
particle.offset.y += particle.speed;
// Follow mouse with some lag
particle.shift.x += (mouseX - particle.shift.x) * particle.speed;
particle.shift.y += (mouseY - particle.shift.y) * particle.speed;
// Apply position
particle.position.x =
particle.shift.x +
Math.cos(i + particle.offset.x) * (particle.orbit * RADIUS_SCALE);
particle.position.y =
particle.shift.y +
Math.sin(i + particle.offset.y) * (particle.orbit * RADIUS_SCALE);
// Limit to screen bounds
particle.position.x = Math.max(
Math.min(particle.position.x, SCREEN_WIDTH),
0
);
particle.position.y = Math.max(
Math.min(particle.position.y, SCREEN_HEIGHT),
0
);
particle.size += (particle.targetSize - particle.size) * 0.05;
if (Math.round(particle.size) == Math.round(particle.targetSize)) {
particle.targetSize = 1 + Math.random() * 7;
}
if (particle.position) context.beginPath();
context.fillStyle = particle.fillColor;
context.strokeStyle = particle.fillColor;
context.lineWidth = particle.size;
context.moveTo(lp.x, lp.y);
context.lineTo(particle.position.x, particle.position.y);
context.stroke();
context.arc(
particle.position.x,
particle.position.y,
particle.size / 2,
0,
Math.PI * 2,
true
);
context.fill();
}
}
window.onload = init;
</script>
</body>
</html>
Currently, the older trails will not fade away and it is creating something more of like a paint effect which I don't want.

One way to fade out your particles is to replace your (currently transparent) drawRect call with a drawImage that draws semi-transparent copy of your background image over each frame before adding particles to the current frame:
In your loop() function:
// Instead of this:
// context.fillStyle = "rgba(0, 0, 0, 0)";
// context.fillRect(0, 0, context.canvas.width, context.canvas.height);
// Do this:
context.save();
context.globalAlpha = 0.1;
context.drawImage(slider_image, 0, 0, canvas.width, canvas.height);
context.restore();
for (i = 0, len = particles.length; i < len; i++) {
...

How do I get this canvas animation script to work in Firefox?

I wrote this canvas animation script in hopes to use it on my portfolio website, but it is basically non-functional in Firefox, and I am not sure why. The script draws stars on the canvas that slowly rotate, and if you hold down the mouse button they spin faster creating trails. It works awesome in chrome, but is extremely slow and choppy in Firefox.
let canvas = document.querySelector('canvas');
let c = canvas.getContext('2d');
canvas.width = window.innerWidth;
canvas.height = window.innerHeight;
let mouse = {
x: window.innerWidth / 2,
y: window.innerHeight / 2
}
let stars = [];
const starCount = 800;
class Star {
constructor(x, y, radius, color){
this.x = x;
this.y = y;
this.radius = radius;
this.color = color;
this.draw = () => {
c.save();
c.beginPath();
c.arc(this.x, this.y, this.radius, 0, Math.PI * 2);
c.fillStyle = this.color;
c.shadowColor = this.color;
c.shadowBlur = 15;
c.fill();
c.closePath();
c.restore();
};
this.update = () => {
this.draw();
};
}
}
let colors = [
"#A751CC",
"#DE9AF9",
"#F9E0F9",
"#B5ECFB",
"#5F86F7"
];
(initializeStars = () =>{
for(let i = 0; i < starCount; i++){
let randomColorIndex = Math.floor(Math.random() * 5);
let randomRadius = Math.random() * 2;
let x = (Math.random() * (canvas.width + 400)) - (canvas.width + 400) / 2;
let y = (Math.random() * (canvas.width + 400)) - (canvas.width + 400) / 2;
stars.push(new Star(x, y, randomRadius, colors[randomColorIndex]));
}
})();
let opacity = 1;
let speed = 0.0005;
let time = 0;
let spinSpeed = desiredSpeed => {
speed += (desiredSpeed - speed) * 0.01;
time += speed;
return time;
}
let starOpacity = (desiredOpacity, ease) => {
opacity += (desiredOpacity - opacity) * ease;
return c.fillStyle = `rgba(18, 18, 18, ${opacity})`;
}
let animate = () => {
window.requestAnimationFrame(animate);
c.save();
if(mouseDown){
starOpacity(0.01, 0.03);
spinSpeed(0.012);
}else{
starOpacity(1, 0.01);
spinSpeed(0.001);
}
c.fillRect(0,0, canvas.width, canvas.height);
c.translate(canvas.width / 2, canvas.height / 2);
c.rotate(time);
for(let i = 0; i < stars.length; i++){
stars[i].update();
}
c.restore();
}
window.addEventListener('mousemove', e => {
mouse.x = e.clientX - canvas.width / 2;
mouse.y = e.clientY - canvas.height / 2;
});
window.addEventListener('resize', () => {
canvas.width = window.innerWidth;
canvas.height = window.innerHeight;
stars = [];
initializeStars();
});
let mouseDown = false;
window.addEventListener("mousedown", () =>{
mouseDown = true;
});
window.addEventListener("mouseup", () => {
mouseDown = false;
});
animate();
Here is the link to the demo on Code Pen; any help is appreciated.

You can use rect instead of arc to draw your stars:
c.rect(this.x, this.y, 2*this.radius, 2*this.radius);
remove the blur It's extremely expensive:
//c.shadowBlur = 15;
You can use a radial gradient going from opaque in the center to transparent in his stead.

How to run multiple instances of a single object JavaScript

Currently attempting to make a physics simulation for elastic collisions of circles. I am having an issue where I do not know how to run the simulation with two circles interacting at the same time. I am not yet looking to create the interaction between the circles just to have them both running simultaneously. Any help is much appreciated. This is my first post so I apologize if I formatted something incorrectly.
var width = 400;
var height = 400;
var canvas = ctx = false;
var frameRate = 1 / 60; // Seconds
var frameDelay = frameRate * 1000; // ms
var loopTimer = false;
var ball = {
position: {
x: width / 2,
y: height / 2
},
velocity: {
x: 0,
y: 0
},
radius: 15, // 1px = 1cm
restitution: -1
};
var mouse = {
x: 0,
y: 0,
isDown: false
};
function getMousePosition(event) {
mouse.x = event.pageX - canvas.offsetLeft;
mouse.y = event.pageY - canvas.offsetTop;
}
var mouseDown = function(event) {
if (event.which == 1) {
getMousePosition(event);
mouse.isDown = true;
ball.position.x = mouse.x;
ball.position.y = mouse.y;
}
}
var mouseUp = function(event) {
if (event.which == 1) {
mouse.isDown = false;
ball.velocity.y = (ball.position.y - mouse.y) / 10;
ball.velocity.x = (ball.position.x - mouse.x) / 10;
}
}
var setup = function() {
canvas = document.getElementById("canvas");
ctx = canvas.getContext("2d");
canvas.onmousemove = getMousePosition;
canvas.onmousedown = mouseDown;
canvas.onmouseup = mouseUp;
ctx.fillStyle = 'blue';
ctx.strokeStyle = '#000000';
loopTimer = setInterval(loop, frameDelay);
}
var loop = function() {
if (!mouse.isDown) {
ball.position.x += ball.velocity.x * frameRate * 100;
ball.position.y += ball.velocity.y * frameRate * 100;
}
if (ball.position.y > height - ball.radius) {
ball.velocity.y *= ball.restitution;
ball.position.y = height - ball.radius;
}
if (ball.position.x > width - ball.radius) {
ball.velocity.x *= ball.restitution;
ball.position.x = width - ball.radius;
}
if (ball.position.x < ball.radius) {
ball.velocity.x *= ball.restitution;
ball.position.x = ball.radius;
}
if (ball.position.y < ball.radius) {
ball.velocity.y *= ball.restitution;
ball.position.y = ball.radius;
}
ctx.clearRect(0, 0, width, height);
ctx.save();
ctx.translate(ball.position.x, ball.position.y);
ctx.beginPath();
ctx.arc(0, 0, ball.radius, 0, Math.PI * 2, true);
ctx.fill();
ctx.closePath();
ctx.restore();
if (mouse.isDown) {
ctx.beginPath();
ctx.moveTo(ball.position.x, ball.position.y);
ctx.lineTo(mouse.x, mouse.y);
ctx.stroke();
ctx.closePath();
}
}
setup();
#canvas {
border: solid 1px #ccc;
}
<canvas id="canvas"></canvas>

Here is how I would do it:
Instead of making the ball a kind of static object I made a constructor function (More about that here).
Then I made a ball array to store all the balls.
To make the dragging possible I store a seperate ball, which is not being moved by "physics" in the newBall variable. This ball is either invisible or is the ball currently being dragged.
In mouseDown() the newBall gets positioned under the cursor.
In mouseUp() it gets it's velocity and gets added to the array of animated balls. Also a new newBall gets created.
In loop() I loop two times through the array of animated balls. Once for the physics, once for the painting.
(Normally you would use two different methods with different tickRates to make animation more smooth, because physics calculation doesn't need to happen 60 times per second.
var width = 400;
var height = 400;
var canvas = ctx = false;
var frameRate = 1 / 60; // Seconds
var frameDelay = frameRate * 1000; // ms
var loopTimer = false;
function ball() {
this.position = {
x: width / 2,
y: height / 2
};
this.velocity = {
x: 0,
y: 0
};
this.radius = 15; // 1px = 1cm
this.restitution = -1
};
var balls = [];
var newBall = new ball();
var mouse = {
x: 0,
y: 0,
isDown: false
};
function getMousePosition(event) {
mouse.x = event.pageX - canvas.offsetLeft;
mouse.y = event.pageY - canvas.offsetTop;
}
var mouseDown = function(event) {
if (event.which == 1) {
getMousePosition(event);
mouse.isDown = true;
newBall.position.x = mouse.x;
newBall.position.y = mouse.y;
}
}
var mouseUp = function(event) {
if (event.which == 1) {
mouse.isDown = false;
newBall.velocity.y = (newBall.position.y - mouse.y) / 10;
newBall.velocity.x = (newBall.position.x - mouse.x) / 10;
balls.push(newBall);
newBall = new ball();
}
}
var setup = function() {
canvas = document.getElementById("canvas");
ctx = canvas.getContext("2d");
canvas.onmousemove = getMousePosition;
canvas.onmousedown = mouseDown;
canvas.onmouseup = mouseUp;
ctx.fillStyle = 'blue';
ctx.strokeStyle = '#000000';
loopTimer = setInterval(loop, frameDelay);
}
var loop = function() {
for (var ball of balls) {
ball.position.x += ball.velocity.x * frameRate * 100;
ball.position.y += ball.velocity.y * frameRate * 100;
if (ball.position.y > height - ball.radius) {
ball.velocity.y *= ball.restitution;
ball.position.y = height - ball.radius;
}
if (ball.position.x > width - ball.radius) {
ball.velocity.x *= ball.restitution;
ball.position.x = width - ball.radius;
}
if (ball.position.x < ball.radius) {
ball.velocity.x *= ball.restitution;
ball.position.x = ball.radius;
}
if (ball.position.y < ball.radius) {
ball.velocity.y *= ball.restitution;
ball.position.y = ball.radius;
}
}
ctx.clearRect(0, 0, width, height);
for (var ball of balls) {
ctx.save();
ctx.translate(ball.position.x, ball.position.y);
ctx.beginPath();
ctx.arc(0, 0, ball.radius, 0, Math.PI * 2, true);
ctx.fill();
ctx.closePath();
ctx.restore();
}
ctx.save();
ctx.translate(newBall.position.x, newBall.position.y);
ctx.beginPath();
ctx.arc(0, 0, newBall.radius, 0, Math.PI * 2, true);
ctx.fill();
ctx.closePath();
ctx.restore();
if (mouse.isDown) {
ctx.beginPath();
ctx.moveTo(newBall.position.x, newBall.position.y);
ctx.lineTo(mouse.x, mouse.y);
ctx.stroke();
ctx.closePath();
}
}
setup();
#canvas {
border: solid 1px #ccc;
}
<canvas id="canvas"></canvas>
Now to get a bit more complex:
I added tickDelay and tickTimer to use them in a tickLoop
The ball constructor now has two methods:
show() draws the ball on the canvas
tick() does the pysics stuff (dt= deltaTime: time since last tick)
newBall is now null if the mouse isn't pressed
setup() initializes the width and height according to the <canvas> elements real size
tick() loops through the balls and calls .tick() tickDelay is in milliseconds so it gets divided by 1000
drawFrame() is your former loop() and does the drawing stuff
var width = 400;
var height = 400;
var canvas = ctx = false;
var frameRate = 1 / 60; // Seconds
var frameDelay = frameRate * 1000; // ms
var tickDelay = frameDelay * 2; //ticks 2 times slower than frames
var frameTimer;
var tickTimer;
function ball() {
this.position = {
x: width / 2,
y: height / 2
};
this.velocity = {
x: 0,
y: 0
};
this.radius = 15; // 1px = 1cm
this.restitution = -.99;
this.show = function() {
ctx.save();
ctx.translate(this.position.x, this.position.y);
ctx.beginPath();
ctx.arc(0, 0, this.radius, 0, Math.PI * 2, true);
ctx.fill();
ctx.closePath();
ctx.restore();
};
this.tick = function(dt) {
this.position.x += this.velocity.x * dt;
this.position.y += this.velocity.y * dt;
if (this.position.y > height - this.radius) {
this.velocity.y *= this.restitution;
this.position.y = height - this.radius;
}
if (this.position.x > width - this.radius) {
this.velocity.x *= this.restitution;
this.position.x = width - this.radius;
}
if (this.position.x < this.radius) {
this.velocity.x *= this.restitution;
this.position.x = this.radius;
}
if (this.position.y < this.radius) {
this.velocity.y *= this.restitution;
this.position.y = this.radius;
}
}
};
var balls = [];
var newBall;
var mouse = {
x: 0,
y: 0,
isDown: false
};
function getMousePosition(event) {
mouse.x = event.pageX - canvas.offsetLeft;
mouse.y = event.pageY - canvas.offsetTop;
}
function mouseDown(event) {
if (event.which == 1) {
getMousePosition(event);
mouse.isDown = true;
if (!newBall) newBall = new ball();
newBall.position.x = mouse.x;
newBall.position.y = mouse.y;
}
}
function mouseUp(event) {
if (event.which == 1) {
mouse.isDown = false;
newBall.velocity.y = (newBall.position.y - mouse.y);
newBall.velocity.x = (newBall.position.x - mouse.x);
balls.push(newBall);
newBall = null;
}
}
function setup() {
canvas = document.getElementById("canvas");
width = canvas.getBoundingClientRect().width;
height = canvas.getBoundingClientRect().height;
ctx = canvas.getContext("2d");
canvas.onmousemove = getMousePosition;
canvas.onmousedown = mouseDown;
canvas.onmouseup = mouseUp;
ctx.fillStyle = 'blue';
ctx.strokeStyle = '#000000';
requestAnimationFrame(drawFrame);
frameTimer = setInterval(drawFrame, frameDelay);
tickTimer = setInterval(tick, tickDelay);
}
function tick() {
for (var ball of balls) ball.tick(tickDelay * .001);
}
function drawFrame() {
ctx.clearRect(0, 0, width, height);
for (var ball of balls) ball.show();
if (newBall) newBall.show(ctx);
if (mouse.isDown && newBall) {
ctx.beginPath();
ctx.moveTo(newBall.position.x, newBall.position.y);
ctx.lineTo(mouse.x, mouse.y);
ctx.stroke();
ctx.closePath();
}
}
setup();
#canvas {
border: solid 1px #ccc;
}
<canvas id="canvas"></canvas>

A really simple way would to do exactly the same as you do now, but not initiate all functions as a variable. Change all the variables that are functions to just functions, and where you call them. At least the variable called ball. Then after that you could make two variables like this
ball1 = new ball();
ball2 = new ball();
Your script is kind of messy so hard for me to say if this will go through without any errors, but if it does, I am more than happy to help. This is not the very best solution if you only go for the way i presented now so please do not use this as you solution, but more as a way to get started. Also you will not really learn anything of it if we just gave you the answer
Edit:
Another thing to mark is that using setInterval for games and graphical projects may be a bad idea since JavaScript is single threaded. A better solution is using requestAnimationFrame()
It would look something like this
function mainLoop() {
update();
draw();
requestAnimationFrame(mainLoop);
}
// Start things off
requestAnimationFrame(mainLoop);

Canvas scalable arc position

http://jsfiddle.net/cs5Sg/11/
I want to do the scalable canvas. I created two circles (arcs) and one line, when you click on circle and move it, the line will follow and change position. The problem is when I added code for resize:
var canvas = document.getElementById('myCanvas'),
context = canvas.getContext('2d'),
radius = 12,
p = null,
point = {
p1: { x:100, y:250 },
p2: { x:400, y:100 }
},
moving = false;
window.addEventListener("resize", OnResizeCalled, false);
function OnResizeCalled() {
var gameWidth = window.innerWidth;
var gameHeight = window.innerHeight;
var scaleToFitX = gameWidth / 800;
var scaleToFitY = gameHeight / 480;
var currentScreenRatio = gameWidth / gameHeight;
var optimalRatio = Math.min(scaleToFitX, scaleToFitY);
if (currentScreenRatio >= 1.77 && currentScreenRatio <= 1.79) {
canvas.style.width = gameWidth + "px";
canvas.style.height = gameHeight + "px";
}
else {
canvas.style.width = 800 * optimalRatio + "px";
canvas.style.height = 480 * optimalRatio + "px";
}
}
function init() {
return setInterval(draw, 10);
}
canvas.addEventListener('mousedown', function(e) {
for (p in point) {
var
mouseX = e.clientX - 1,
mouseY = e.clientY - 1,
distance = Math.sqrt(Math.pow(mouseX - point[p].x, 2) + Math.pow(mouseY - point[p].y, 2));
if (distance <= radius) {
moving = p;
break;
}
}
});
canvas.addEventListener('mouseup', function(e) {
moving = false;
});
canvas.addEventListener('mousemove', function(e) {
if(moving) {
point[moving].x = e.clientX - 1;
point[moving].y = e.clientY - 1;
}
});
function draw() {
context.clearRect(0, 0, canvas.width, canvas.height);
context.beginPath();
context.moveTo(point.p1.x,point.p1.y);
context.lineTo(point.p2.x,point.p2.y);
context.closePath();
context.fillStyle = '#8ED6FF';
context.fill();
context.stroke();
for (p in point) {
context.beginPath();
context.arc(point[p].x,point[p].y,radius,0,2*Math.PI);
context.fillStyle = 'red';
context.fill();
context.stroke();
}
context.closePath();
}
init();
The canvas is scalable, but the problem is with the points (circles). When you change the window size, they still have the same position on the canvas area, but the distance change (so the click option fails). How to fix that?

Live Demo
Basically you just need a scaler value that takes into account the actual dimensions of the canvas, and the css dimensions like so
var scaledX = canvas.width/ canvas.offsetWidth,
scaledY = canvas.height/ canvas.offsetHeight;
And then every time the window is resized you need to make sure to update the scaler values.
function OnResizeCalled() {
scaledX = canvas.width/ canvas.offsetWidth;
scaledY = canvas.height/ canvas.offsetHeight;
}
To get the correct coords you need to multiply the clientX and clientY by the scaler in all of your mouse events
canvas.addEventListener('mousedown', function(e) {
for (p in point) {
var
mouseX = e.clientX*scaledX,
mouseY = e.clientY*scaledY,
distance = Math.sqrt(Math.pow(mouseX - point[p].x, 2) + Math.pow(mouseY - point[p].y, 2));
if (distance <= radius) {
moving = p;
break;
}
}
});
canvas.addEventListener('mousemove', function(e) {
var mouseX = e.clientX*scaledX,
mouseY = e.clientY*scaledY;
if(moving) {
point[moving].x = mouseX;
point[moving].y = mouseY;
}
});
Full code
var canvas = document.getElementById('myCanvas'),
context = canvas.getContext('2d'),
radius = 12,
p = null,
point = {
p1: { x:100, y:250},
p2: { x:400, y:100}
},
moving = false,
scaledX = canvas.width/ canvas.offsetWidth,
scaledY = canvas.height/ canvas.offsetHeight;
window.addEventListener("resize", OnResizeCalled, false);
function OnResizeCalled() {
var gameWidth = window.innerWidth;
var gameHeight = window.innerHeight;
var scaleToFitX = gameWidth / 800;
var scaleToFitY = gameHeight / 480;
var currentScreenRatio = gameWidth / gameHeight;
var optimalRatio = Math.min(scaleToFitX, scaleToFitY);
if (currentScreenRatio >= 1.77 && currentScreenRatio <= 1.79) {
canvas.style.width = gameWidth + "px";
canvas.style.height = gameHeight + "px";
}
else {
canvas.style.width = 800 * optimalRatio + "px";
canvas.style.height = 480 * optimalRatio + "px";
}
scaledX = canvas.width/ canvas.offsetWidth;
scaledY = canvas.height/ canvas.offsetHeight;
}
function init() {
return setInterval(draw, 10);
}
canvas.addEventListener('mousedown', function(e) {
for (p in point) {
var
mouseX = e.clientX*scaledX,
mouseY = e.clientY*scaledY,
distance = Math.sqrt(Math.pow(mouseX - point[p].x, 2) + Math.pow(mouseY - point[p].y, 2));
if (distance <= radius) {
moving = p;
break;
}
}
});
canvas.addEventListener('mouseup', function(e) {
moving = false;
});
canvas.addEventListener('mousemove', function(e) {
var mouseX = e.clientX*scaledX,
mouseY = e.clientY*scaledY;
if(moving) {
point[moving].x = mouseX; //1 is the border of your canvas
point[moving].y = mouseY;
}
});
function draw() {
context.clearRect(0, 0, canvas.width, canvas.height);
context.beginPath();
context.moveTo(point.p1.x,point.p1.y);
context.lineTo(point.p2.x,point.p2.y);
context.closePath();
context.fillStyle = '#8ED6FF';
context.fill();
context.stroke();
for (p in point) {
context.beginPath();
context.arc(point[p].x,point[p].y,radius,0,2*Math.PI);
context.fillStyle = 'red';
context.fill();
context.stroke();
}
context.closePath();
}
init();