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Fade out tiles in canvas image

Still learning Canvas. How can I fade out each tile in an image that I have as Image Data in an array:
for (let i = 0; i < tilesY; i++) {
for (let j = 0; j < tilesX; j++) {
this.ctxTile.putImageData(this.tileData[itr], j * tileWidth, i * tileHeight);
itr += 1
}
}
I understand that the solution must have something to do with compositing? I want to fade out each tile individually. The putImageData works and the image is inside canvas, and assembled as a set of tiles.
Thanks

Usually you'd just play with the ctx.globalAlpha property at the time of drawing to your context to set your tile's alpha. However, putImageData is kind of a strange beast in the API in that it ignores the context transformation, clipping areas and in our case compositing rules, including globalAlpha.
So one hack around would be to "erase" the given tile after we've drawn it. For this we can use the globalCompositeOperation = "destination-out" property that we'll use on a call to a simple fillRect() with the inverse globalAlpha we want. (Luckily putImageData always draws only rectangles).
const canvas = document.querySelector("canvas");
const ctx = canvas.getContext("2d");
const tileWidth = 50;
const tileHeight = 50;
class Tile {
constructor(x, y, width, height) {
this.x = Math.round(x); // putImageData only renders at integer coords
this.y = Math.round(y);
this.width = width;
this.height = height;
this.img = buildImageData(width, height);
this.alpha = 1;
}
isPointInPath(x, y) {
return x >= this.x && x <= this.x + this.width &&
y >= this.y && y <= this.y + this.height;
}
draw() {
ctx.putImageData(this.img, this.x, this.y);
ctx.globalAlpha = 1 - this.alpha; // inverse alpha
// the next drawing will basically erase what it represents
ctx.globalCompositeOperation = "destination-out";
ctx.fillRect(this.x, this.y, this.width, this.height);
// restore the context
ctx.globalAlpha = 1;
ctx.globalCompositeOperation = "source-over";
}
}
const tiles = Array.from({ length: 5 }, (_, i) => new Tile(i * tileWidth * 1.25, 0, tileWidth, tileHeight));
canvas.onclick = (e) => {
const x = e.clientX - canvas.offsetLeft;
const y = e.clientY - canvas.offsetTop;
const clickedTile = tiles.find((tile) => tile.isPointInPath(x, y));
if (clickedTile) { clickedTile.alpha -= 0.1 };
redraw();
};
redraw();
function redraw() {
ctx.clearRect(0, 0, canvas.width, canvas.height);
tiles.forEach((tile) => tile.draw());
}
function buildImageData(width, height) {
const img = new ImageData(width, height);
const arr = new Uint32Array(img.data.buffer);
for (let i = 0; i < arr.length; i++) {
arr[i] = Math.random() * 0xFFFFFF + 0xFF000000;
}
return img;
}
<p>Click on each tile to lower its alpha.</p>
<canvas></canvas>
However this means that for each tile we have one putImageData + one composited fillRect. If you've got a lot of tiles, that makes for a pretty big overhead.
So instead the best might be to convert all your ImageData objects to ImageBitmap ones. To understand the difference between both I invite you to read this answer of mine.
Once we have ImageBitmaps, we can apply the globalAlpha on our draw call directly:
const canvas = document.querySelector("canvas");
const ctx = canvas.getContext("2d");
const tileWidth = 50;
const tileHeight = 50;
class Tile {
constructor(x, y, width, height) {
this.x = Math.round(x); // putImageData only renders at integer coords
this.y = Math.round(y);
this.width = width;
this.height = height;
this.alpha = 1;
const imgData = buildImageData(width, height);
// createImageBitmap is "async"
this.ready = createImageBitmap(imgData)
.then((bmp) => this.img = bmp);
}
isPointInPath(x, y) {
return x >= this.x && x <= this.x + this.width &&
y >= this.y && y <= this.y + this.height;
}
draw() {
// single draw per tile
ctx.globalAlpha = this.alpha;
ctx.drawImage(this.img, this.x, this.y, this.width, this.height);
ctx.globalAlpha = 1;
}
}
const tiles = Array.from({ length: 5 }, (_, i) => new Tile(i * tileWidth * 1.25, 0, tileWidth, tileHeight));
canvas.onclick = (e) => {
const x = e.clientX - canvas.offsetLeft;
const y = e.clientY - canvas.offsetTop;
const clickedTile = tiles.find((tile) => tile.isPointInPath(x, y));
if (clickedTile) { clickedTile.alpha -= 0.1 };
redraw();
};
// wait for all the ImageBitmaps are generated
Promise.all(tiles.map((tile) => tile.ready)).then(redraw);
function redraw() {
ctx.clearRect(0, 0, canvas.width, canvas.height);
tiles.forEach((tile) => tile.draw());
}
function buildImageData(width, height) {
const img = new ImageData(width, height);
const arr = new Uint32Array(img.data.buffer);
for (let i = 0; i < arr.length; i++) {
arr[i] = Math.random() * 0xFFFFFF + 0xFF000000;
}
return img;
}
<p>Click on each tile to lower its alpha.</p>
<canvas></canvas>

Gaming functions

I'm trying to get my objects to move in full motion in a <canvas> with things I do understand about javascript (although it's not much yet). I had to do a ton of research but I'm getting nowhere.
Im trying to get my game character, which is in the class of Player, to move. However, it isn't moving with my arrow keys. The console is receiving the logs from my function, but the character isn't moving.
JS dump:
const canvas = document.getElementById('Game-Screen');
const ctx = canvas.getContext('2d');
canvas.width = 1200;
canvas.height = 900;
class Player {
constructor(x, y, radius, speed, x_velocity, y_velocity, forward) {
this.x = x;
this.y = y;
this.radius = radius;
this.speed = speed;
this.x_velocity = x_velocity;
this.y_velocity = y_velocity;
this.forward = forward = true;
}
Appear() {
ctx.beginPath();
ctx.arc(this.x, this.y, this.radius, 0, Math.PI * 2);
ctx.closePath();
ctx.fill();
}
};
controls = {
right: false,
left: false,
up: false,
keyEvent: function(pressed) {
let keyCondition = (pressed.type == 'keydown') ? true : false;
console.log(keyCondition);
switch (pressed.keyCode) {
case 37: //will go left
controls.left = keyCondition;
break;
case 38: //will go up
controls.up = keyCondition;
break;
case 39: // will go down
controls.right = keyCondition;
break;
}
}
};
const movement = function() {
if (controls.up && Ship.forward == false) {
Ship.y_velocity -= 20;
Ship.forward = true;
}
if (controls.left) {
Ship.x_velocity -= 0.5;
}
if (controls.right) {
Ship.x_velocity += 0.5;
}
controls.y_velocity += 1.5;
controls.x += controls.x_velocity;
controls.y += controls.y_velocity;
controls.x_velocity += 0.9;
controls.y_velocity += 0.9;
};
window.addEventListener('keydown', controls.keyEvent);
window.addEventListener('keyup', controls.keyEvent);
const Ship = new Player(550, 800, 25, 0, 0);
const Astroids = [];
Ship.Appear();
function update() {
this.x = this.x + this.x_velocity.x
this.y = this.y + this.y_velocity.y
}
class Astroider {
constructor(x, y, radius, speed, x_velocity, y_velocity, forward) {
this.x = x;
this.y = y;
this.radius = radius;
this.speed = speed;
this.x_velocity = x_velocity;
this.y_velocity = y_velocity;
this.forward = forward = true;
}
Appear() {
ctx.beginPath();
// x y
ctx.arc(this.x, this.y, this.radius, 0, Math.PI * 2);
ctx.closePath();
ctx.fill();
}
};
const Astro = new Astroider(600, 200, 40, 0, 0)
function spawnAstroids() {
setInterval(() => {
const x = 200
const y = 300
const radius = 40
const color = 'grey';
const velocity = {
x: 1,
y: 1
}
Astroid.push(new Astroider(x, y, radius, color, velocity))
}, 2000)
console.log(Astroid);
}
Astroid = [];

How to detect when mouse is outside of a certain circle?

When a mouse is hovering a image. It gets detect by this if statement:
if ((distance(circles[this.index].x, circles[this.index].y, mouse.x, mouse.y)) < circles[this.index].radius)
I also want to detect when a mouse it outside a image.
After that previous if statement I cannot use else the reason is because:
When I generate multiple images on screen and when my mouse if hovering over 1 image. It does hover of that image and the code detects it but it also doesnt hover of all the other images. That is the reason that is display 4 times "outside circle" and 1 time "inside circle"
As seen in the log:
Console.log output:
Mouse inside circle
Mouse outside circle 4
Mouse inside circle
Mouse outside circle 4
Im looking for a way the detect when the mouse is leaving a circle.
You can find the code I'm working with below:
PS: it it important that it detect in what (index) circle the mouse is and leaves.
I want to create a huge amount of pictures, but in the code below I used 5 for demo purpeses.
var mouse = {
x: innerWidth / 2,
y: innerHeight / 2
};
// Mouse Event Listeners
addEventListener('mousemove', event => {
mouse.x = event.clientX;
mouse.y = event.clientY;
});
//Calculate distance between 2 objects
function distance(x1, y1, x2, y2) {
let xDistance = x2 - x1;
let yDistance = y2 - y1;
return Math.sqrt(Math.pow(xDistance, 2) + Math.pow(yDistance, 2));
}
// Sqaure to circle
function makeCircleImage(radius, src, callback) {
var canvas = document.createElement('canvas');
canvas.width = canvas.height = radius * 2;
var ctx = canvas.getContext("2d");
var img = new Image();
img.src = src;
img.onload = function() {
ctx.drawImage(img, 0, 0, canvas.width, canvas.height);
// we use compositing, offers better antialiasing than clip()
ctx.globalCompositeOperation = 'destination-in';
ctx.arc(radius, radius, radius, 0, Math.PI*2);
ctx.fill();
callback(canvas);
};
}
function Circle( x, y, radius, index ) {
//Give var for circle
this.x = x;
this.y = y;
this.dx = 1;
this.dy = 1;
this.radius = radius;
this.index = index;
}
// use prototyping if you wish to make it a class
Circle.prototype = {
//Draw circle on canvas
draw: function () {
var
x = (this.x - this.radius),
y = (this.y - this.radius);
// draw is a single call
c.drawImage( this.image, x, y );
},
//Updates position of images
update: function () {
var
max_right = canvas.width + this.radius,
max_left = this.radius * -1;
this.x += this.dx;
if( this.x > max_right ) {
this.x += max_right - this.x;
this.dx *= -1;
}
if( this.x < max_left ) {
this.x += max_left - this.x;
this.dx *= -1;
}
if ((distance(circles[this.index].x, circles[this.index].y, mouse.x, mouse.y)) < circles[this.index].radius) {
// Mouse inside circle
console.log("Mouse inside circle")
} else{
//The mouse is in one circle
//And out of 4 other circles
console.log("Mouse outside circle")
}
},
init: function(callback) {
var url = "https://t4.ftcdn.net/jpg/02/26/96/25/240_F_226962583_DzHr45pyYPdmwnjDoqz6IG7Js9AT05J4.jpg";
makeCircleImage( this.radius, url, function(img) {
this.image = img;
callback();
}.bind(this));
}
};
//Animate canvas
function animate() {
c.clearRect(0, 0, window.innerWidth, window.innerHeight);
circles.forEach(function( circle ) {
circle.update();
});
circles.forEach(function( circle ) {
circle.draw();
});
requestAnimationFrame(animate);
}
//Init canvas
var canvas = document.querySelector('canvas');
var c = canvas.getContext('2d');
canvas.width = window.innerWidth;
canvas.height = window.innerHeight;
//init circle objects
var circles = [
new Circle(10, 100, 50,0),
new Circle(10, 200, 30,1),
new Circle(10, 300, 50,2),
new Circle(10, 400, 50,3),
new Circle(10, 500, 50,4)
];
var ready = 0;
circles.forEach(function(circle) {
circle.init(oncircledone);
});
function oncircledone() {
if(++ready === circles.length) {
animate()
}
}
<canvas></canvas>

just add another property to circle
function Circle(x, y, radius, index) {
//Give var for circle
this.x = x;
this.y = y;
this.dx = 1;
this.dy = 1;
this.radius = radius;
this.index = index;
this.mouseInside = false
}
and then the update logic change to this
if ((distance(this.x, this.y, mouse.x, mouse.y)) < circles[this.index].radius) {
if (!this.mouseInside) {
this.mouseInside = true
console.log(`mouse enter circele at ${this.index}`)
}
}
else if (this.mouseInside) {
this.mouseInside = false
console.log(`mouse leave circele at ${this.index}`)
}
check if circles overlap and the you can decide if you want to update
var overlapsCircles = circles.filter(circle => {
var diffrentId = circle.index != this.index
var overlapping =
distance(this.x, this.y, circle.x, circle.y) < this.radius
return diffrentId && overlapping
})
if (overlapsCircles.length > 0) {
var overlapCircle = overlapsCircles.map(circle => circle.index)
console.log('overlap circle with index ' + overlapCircle)
}
var mouse = {
x: innerWidth / 2,
y: innerHeight / 2
};
// Mouse Event Listeners
addEventListener('mousemove', event => {
mouse.x = event.clientX;
mouse.y = event.clientY;
});
//Calculate distance between 2 objects
function distance(x1, y1, x2, y2) {
let xDistance = x2 - x1;
let yDistance = y2 - y1;
return Math.sqrt(Math.pow(xDistance, 2) + Math.pow(yDistance, 2));
}
// Sqaure to circle
function makeCircleImage(radius, src, callback) {
var canvas = document.createElement('canvas');
canvas.width = canvas.height = radius * 2;
var ctx = canvas.getContext("2d");
var img = new Image();
img.src = src;
img.onload = function () {
ctx.drawImage(img, 0, 0, canvas.width, canvas.height);
// we use compositing, offers better antialiasing than clip()
ctx.globalCompositeOperation = 'destination-in';
ctx.arc(radius, radius, radius, 0, Math.PI * 2);
ctx.fill();
callback(canvas);
};
}
function Circle(x, y, radius, index) {
//Give var for circle
this.x = x;
this.y = y;
this.dx = 1;
this.dy = 1;
this.radius = radius;
this.index = index;
this.mouseInside = false
}
// use prototyping if you wish to make it a class
Circle.prototype = {
//Draw circle on canvas
draw: function () {
var
x = (this.x - this.radius),
y = (this.y - this.radius);
// draw is a single call
c.drawImage(this.image, x, y);
},
//Updates position of images
update: function () {
var
max_right = canvas.width + this.radius,
max_left = this.radius * -1;
this.x += this.dx;
if (this.x > max_right) {
this.x += max_right - this.x;
this.dx *= -1;
}
if (this.x < max_left) {
this.x += max_left - this.x;
this.dx *= -1;
}
if ((distance(this.x, this.y, mouse.x, mouse.y)) < circles[this.index].radius) {
if (!this.mouseInside) {
this.mouseInside = true
console.log(`mouse enter circele at ${this.index}`)
}
}
else if (this.mouseInside) {
this.mouseInside = false
console.log(`mouse leave circele at ${this.index}`)
}
},
init: function (callback) {
var url = "https://t4.ftcdn.net/jpg/02/26/96/25/240_F_226962583_DzHr45pyYPdmwnjDoqz6IG7Js9AT05J4.jpg";
makeCircleImage(this.radius, url, function (img) {
this.image = img;
callback();
}.bind(this));
}
};
//Animate canvas
function animate() {
c.clearRect(0, 0, window.innerWidth, window.innerHeight);
circles.forEach(function (circle) {
circle.update();
});
circles.forEach(function (circle) {
circle.draw();
});
requestAnimationFrame(animate);
}
//Init canvas
var canvas = document.querySelector('canvas');
var c = canvas.getContext('2d');
canvas.width = window.innerWidth;
canvas.height = window.innerHeight;
//init circle objects
var circles = [
new Circle(10, 100, 50, 0),
new Circle(10, 200, 30, 1),
new Circle(10, 300, 50, 2),
new Circle(10, 400, 50, 3),
new Circle(10, 500, 50, 4)
];
var ready = 0;
circles.forEach(function (circle) {
circle.init(oncircledone);
});
function oncircledone() {
if (++ready === circles.length) {
animate()
}
}
<canvas id="ctx"></canvas>

Ambiguities
It is not clear what you need in regard to circles and some point (in this answer point is a substitute for mouse and only requires that it have the properties x and y to be valid ).
The lack of information in your question concerns the facts
that many circles can be under the point at the same time.
and that more than one circle can move from under to out or out to under the point per frame.
the wording of the question suggest you are after just one circle which conflicts with the above 2 concerns.
Assumptions
I will assume that the interaction with the circles are more than just a simple on under event like interaction. That they may include animation related behaviors that are triggered by the state related to the point.
I assume that the visual order of the circles will determine how you select circles of interest.
That all circles per frame that meet the required conditions and can be accessed quickly.
That performance is important as you wish to have many circles that interact with a point.
That there is only one point (mouse, touch, other source) per frame that interacts with the circles
There is no requirement for circle circle interaction
Solution
The example below covers the above assumptions and resolves any ambiguities in the question. It is designed to be efficient and flexible.
The circles are stored in an array that has had its properties extended called circles
Rendering and state sets
The function circles.updateDraw(point) updates and draws all the circles. The argument point is a point to check the circle against. It defaults to the mouse.
All circles are drawn with an outline. Circles under the point (eg mouse) are filled with green, Circles just moved to under the point (eg onMouseOver) are filled with yellow, circle that have just move out from under are filled with red.
There are 3 arrays as properties of circles that contain circles as define...
circles.under All circles under the point
circles.outFromUnder All circles just out from under the point
circles.newUnder All circles new to under the point
These array are populated by the function circles.updateDraw(point)
Query all circles point state
Circles also have 3 functions that refer to the above arrays as set the default set is circles.under.
The functions are..
circles.firstInSet(set) Returns the first circle (The visual bottom most) in set or undefined
circles.lastInSet(set) Returns the last circle (The visual top most) in set or undefined
circles.closestInSet(set) Returns the closest circle to the point in set or undefined
For example to get the visual top most circle just under the mouse you would call circles.lastInSet(circles.newUnder) or to get the circle closest to the mouse from all circles under the mouse you would call circles.closestInSet(circles.newUnder) (or as it defaults to set under call circles.closestInSet() )
Circle additional states
Each Circle has some additional properties.
Circle.distSqr is the square of the distance from the point
Circle.rSqr is the square of the radius calculated when constructed.
Circle.underCount This value can be used to apply animations to the circle based on its relative state to the point.
If positive is the number of frames plus 1, the circle is under the point.
If this value is 1 then the circle is just moved from not under to under.
If this value is 0 the it has just moved out from under the point.
If negative this value is the number of frames the circle is not under the point
Running Demo
Use mouse to move over circles.
The circle closest and under the mouse is filled with white with alpha = 0.5
addEventListener('mousemove', event => {
mouse.x = event.clientX;
mouse.y = event.clientY;
});
Math.TAU = Math.PI * 2;
Math.rand = (min, max) => Math.random() * (max - min) + min;
const CIRCLE_RADIUS = 50;
const UNDER_STYLE = "#0A0";
const NEW_UNDER_STYLE = "#FF0";
const OUT_STYLE = "#F00";
const CIRCLE_STYLE = "#000";
const CIRCLE_LINE_WIDTH = 1.5;
const CIRCLE_COUNT = 100;
const CIRCLE_CLOSEST = "#FFF";
const ctx = canvas.getContext('2d');
const mouse = {x: 0, y: 0};
requestAnimationFrame(() => {
sizeCanvas();
var i = CIRCLE_COUNT;
while (i--) {
const r = Math.rand(CIRCLE_RADIUS / 3, CIRCLE_RADIUS);
circles.push(new Circle(
Math.rand(r, canvas.width - r),
Math.rand(r, canvas.height - r),
Math.rand(-1, 1),
Math.rand(-1, 1),
r
));
}
animate()
});
function animate() {
sizeCanvas();
ctx.clearRect(0, 0, ctx.canvas.width, ctx.canvas.height);
circles.updateDraw();
const c = circles.closestInSet(circles.under);
if(c) {
ctx.globalAlpha = 0.5;
ctx.beginPath();
ctx.fillStyle = CIRCLE_CLOSEST;
c.draw();
ctx.fill();
ctx.globalAlpha = 1;
}
requestAnimationFrame(animate);
}
function sizeCanvas() {
if (canvas.width !== innerWidth || canvas.height !== innerHeight) {
canvas.width = innerWidth;
canvas.height = innerHeight;
}
}
function Circle( x, y, dx = 0, dy = 0, radius = CIRCLE_RADIUS) {
this.x = x + radius;
this.y = y + radius;
this.dx = dx;
this.dy = dy;
this.radius = radius;
this.rSqr = radius * radius; // radius squared
this.underCount = 0; // counts frames under point
}
Circle.prototype = {
draw() {
ctx.moveTo(this.x + this.radius, this.y);
ctx.arc(this.x, this.y, this.radius, 0, Math.TAU);
},
update() {
this.x += this.dx;
this.y += this.dy;
if (this.x >= canvas.width - this.radius) {
this.x += (canvas.width - this.radius) - this.x;
this.dx = -Math.abs(this.dx);
} else if (this.x < this.radius) {
this.x += this.radius - this.x;
this.dx = Math.abs(this.dx);
}
if (this.y >= canvas.height - this.radius) {
this.y += (canvas.height - this.radius) - this.y;
this.dy = -Math.abs(this.dx);
} else if (this.y < this.radius) {
this.y += this.radius - this.y;
this.dy = Math.abs(this.dy);
}
},
isUnder(point = mouse) {
this.distSqr = (this.x - point.x) ** 2 + (this.y - point.y) ** 2; // distance squared
return this.distSqr < this.rSqr;
}
};
const circles = Object.assign([], {
under: [],
outFromUnder: [],
newUnder: [],
firstInSet(set = this.under) { return set[0] },
lastInSet(set = this.under) { return set[set.length - 1] },
closestInSet(set = this.under) {
var minDist = Infinity, closest;
if (set.length <= 1) { return set[0] }
for (const circle of set) {
if (circle.distSqr < minDist) {
minDist = (closest = circle).distSqr;
}
}
return closest;
},
updateDraw(point) {
this.under.length = this.newUnder.length = this.outFromUnder.length = 0;
ctx.strokeStyle = CIRCLE_STYLE;
ctx.lineWidth = CIRCLE_LINE_WIDTH;
ctx.beginPath();
for(const circle of this) {
circle.update();
if (circle.isUnder(point)) {
if (circle.underCount <= 0) {
circle.underCount = 1;
this.newUnder.push(circle);
} else { circle.underCount ++ }
this.under.push(circle);
} else if (circle.underCount > 0) {
circle.underCount = 0;
this.outFromUnder.push(circle);
} else {
circle.underCount --;
}
circle.draw();
}
ctx.stroke();
ctx.globalAlpha = 0.75;
ctx.beginPath();
ctx.fillStyle = UNDER_STYLE;
for (const circle of this.under) {
if (circle.underCount > 1) { circle.draw() }
}
ctx.fill();
ctx.beginPath();
ctx.fillStyle = OUT_STYLE;
for (const circle of this.outFromUnder) { circle.draw() }
ctx.fill();
ctx.beginPath();
ctx.fillStyle = NEW_UNDER_STYLE;
for (const circle of this.newUnder) { circle.draw() }
ctx.fill();
ctx.globalAlpha = 1;
}
});
#canvas {
position: absolute;
top: 0px;
left: 0px;
background: #6AF;
}
<canvas id="canvas"></canvas>

Well, the mouse is moving and you can simply create a Set which will contain circle objects that will store the circle(s) you are in:
let circleOfTrust = new Set();
//At the initialization you need to add any circles your point is currently in
and then at the loop:
circles.forEach(function( circle ) {
circleOfTrust[circle.update(circleOfTrust.has(circle)) ? "add" : "delete"](circle);
});
if (circleOfTrust.size() === 0) {
//point is outside the circles
} else {
//point is inside the circles in the set
}
and the update:
update: function (isInside) {
var
max_right = canvas.width + this.radius,
max_left = this.radius * -1;
this.x += this.dx;
if( this.x > max_right ) {
this.x += max_right - this.x;
this.dx *= -1;
}
if( this.x < max_left ) {
this.x += max_left - this.x;
this.dx *= -1;
}
return distance(circles[this.index].x, circles[this.index].y, mouse.x, mouse.y)) < circles[this.index].radius;
},

I would propose the following:
Keep a stack of figures with the order of how they were created (or any other meaningful order). This is needed to detect moves over overlapping figures.
Implement a function/method that iterates the stack and determines if the cursor is inside any of the figures.
Remember the last state, on state transition inside->ouside triggers an event.
function FiguresCollection(canvas, callback)
{
var buffer = [];
var lastHitFigure = null;
var addFigure = function(figure)
{
buffer.push(figure);
}
var onMouseMove = function(e)
{
var currentHit = null;
// iterating from the other end, recently added figures are overlapping previous ones
for (var i= buffer.length-1;i>=0;i--)
{
if (distance(e.offsetX, e.offsetY, buffer[i].x, buffer[i].y) <= buffer[i].radius) {
// the cursor is inside Figure i
// if it come from another figure
if (lastHitFigure !== i)
{
console.log("The cursor had left figure ", lastHitFigure, " and entered ",i);
callback(buffer[i]);
}
lastHitFigure = i;
currentHit = i;
break; // we do not care about figures potentially underneath
}
}
if (lastHitFigure !== null && currentHit == null)
{
console.log("the cursor had left Figure", lastHitFigure, " and is not over any other ");
lastHitFigure = null;
callback(buffer[lastHitFigure]);
}
}
}
canvas.addEventListener("mousemove", onMouseMove);
this.addFigure = addFigure;
}
Now use it:
var col = new FiguresCollection(canvas, c=> console.log("The cursor had left, ", c) );
for(let i in circles)
{
c.addFigure(circles[i]);
}
// I hope I got the code right. I haven't tested it. Please point out any issues or errors.

How to clear a circle drawn with arc in javascript?

I am having problems when drawing a circle. How do I clear it?
I also still want to maintain the transparent background as much as possible as I am planning on making particles rain down. I also would want to not use images to lower the load on the server.
var canvas = document.getElementById("canvas");
canvas.width = window.innerWidth;
canvas.height = window.innerHeight;
var ctx = canvas.getContext("2d");
const ParticleFactory = function(){
this.interval = 100;
this.lastOutput = Date.now();
this.particles = [];
}
ParticleFactory.prototype.tick = function(){
if (Date.now() > this.lastOutput + this.interval) {
const particle = new Particle(500, 100, 4);
this.particles.push(particle);
this.lastOutput = Date.now();
}
for (var i=0; i < this.particles.length; i++) {
this.particles[i].tick();
};
}
ParticleFactory.prototype.draw = function(){
for (var i=0; i < this.particles.length; i++) {
this.particles[i].draw();
};
}
ParticleFactory.prototype.del = function(toDelete){
this.particles = this.particles.filter(item => item !== toDelete);
}
const Particle = function(x, y, r){
this.x = x;
this.y = y;
this.r = r;
}
Particle.prototype.tick = function(){
this.x -= 0.1;
}
Particle.prototype.draw = function(){
ctx.beginPath();
ctx.arc(this.x, this.y, this.r, 0, 2 * Math.PI, false);
ctx.fillStyle = "rgb(0, 0, 255)";
ctx.fill();
ctx.closePath();
}
// Definitions
let particleFactory = new ParticleFactory;
function draw(){
ctx.clearRect(0, 0, canvas.width, canvas.height);
particleFactory.draw();
}
function tick(){
particleFactory.tick();
draw()
window.requestAnimationFrame(tick)
}
document.addEventListener("DOMContentLoaded", function() {
tick();
});
ctx.clearRect() doesn't clear the curcle that is being draws every tick by Particle.draw()
The dot moves and leaves a trail behind even when ctx.clearRect() is run before every draw.

How can I get my firework objects to have random colors like my confetti objects?

I'm making an eCard with falling confetti and fireworks flying up from the bottom of the screen. The logic for both are almost identical:
I make an empty array for fireworks and confetti, and then fill them with objects, using my GetRandom(mix,max) function to create each one with a random value:
//fill confetti object array
for (i = 0; i < NUM_CONFETTI; i++) {
ConfettiArray.push(new Confetti(GetRandom(0,canvas.width), GetRandom(-200,-10), GetRandom(10,30), GetRandom(10,30), colorChoices[GetRandom(0,NUM_COLORS)], GetRandom(0,2*Math.PI),GetRandom(50,80)));
}
//fill firework object array
for (i = 0; i < NUM_FIREWORKS; i++) {
FireworkArray.push(new Firework(GetRandom(0,canvas.width), canvas.height, GetRandom(4,20), colorChoices[GetRandom(0,NUM_COLORS)], GetRandom(30,100), GetRandom(-10,10), GetRandom(50,200)));
}
Then they are drawn and updated in their specific ways, each one starting by setting context.fillStyle and .strokeStyle as the current object's color value:
//confetti.draw
Draw: function(x, y, width, height, color, rotationAngle) {
context.translate(x,y)
context.rotate(rotationAngle)
context.strokeStyle = color;
context.fillStyle = color;
context.beginPath();
context.rect(0, 0, width, height);
context.fill();
context.closePath();
context.resetTransform();
},
//firework.draw
Draw: function(x, y, lineWidth, color, speedY, swayX, blastRadius) {
context.fillStyle = color;
context.strokeStyle = color;
context.moveTo(x,y);
context.lineTo(x-swayX,y-speedY);
context.stroke();
},
Then they are each updated:
//confetti.update
Update: function(modifier) {
this.y = this.y + (this.fallSpeed * modifier);
if (this.y > canvas.height) {this.x = GetRandom(0,canvas.width);this.y = GetRandom(-100,0);}
},
//firework.update
Update: function(modifier) {
this.x = this.x - this.swayX;
this.y = this.y - this.speedY;
if (this.y < -10) {this.x = GetRandom(0,canvas.width);this.y = canvas.height;this.speedY = GetRandom(30,100);this.swayX = GetRandom(-10,10)}
},
I have scoured the code over and over and I just can't seem to get a reason as to why the confetti all has random sizes, angles, fallrates, and colors, AND the fireworks all have random swayX and speedY values but all the same colors. The full code is below if anyone wants to run it in full:
//james gossling multimedia for web design spring 2018
var canvas = document.getElementById('canvas'),
context = canvas.getContext('2d');
var GetRandom = function(min, max) {
//set mins and maxes for ball speed to change angle slightly after ball reset
min = min;
max = max;
return Math.floor(Math.random() * (max - min + 1) + min);
};
//game classes go here
var Background = function(context,color) {
this.context = context;
this.color = color;
};
Background.prototype = {
DrawBackground: function() {
//for testing
//console.log('here')
context.strokeStyle = this.color;
context.fillStyle = this.color;
context.beginPath();
context.rect(0,0,canvas.width,canvas.height);
context.stroke(); // invoke stroke
context.fill(); // invoke fill
context.closePath();
},
};
Confetti = function(x, y, width, height, color, rotationAngle, fallSpeed) {
this.x = x;
this.y = y;
this.width = width;
this.height = height;
this.color = color;
this.rotationAngle = rotationAngle;
this.fallSpeed = fallSpeed;
};
Confetti.prototype = {
Draw: function(x, y, width, height, color, rotationAngle) {
context.translate(x,y)
context.rotate(rotationAngle)
context.strokeStyle = color;
context.fillStyle = color;
context.beginPath();
context.rect(0, 0, width, height);
context.fill();
context.closePath();
context.resetTransform();
},
GetX: function() {
return this.x;
},
GetY: function() {
return this.y;
},
GetWidth: function() {
return this.width;
},
GetHeight: function() {
return this.height;
},
GetColor: function() {
return this.color;
},
GetRotationAngle: function() {
return this.rotationAngle;
},
GetFallSpeed: function() {
return this.fallSpeed;
},
Update: function(modifier) {
this.y = this.y + (this.fallSpeed * modifier);
if (this.y > canvas.height) {this.x = GetRandom(0,canvas.width);this.y = GetRandom(-100,0);}
},
};
var DrawConfetti = function() {
for (i = 0; i < NUM_CONFETTI; i++) {
ConfettiArray[i].Draw(ConfettiArray[i].GetX(),ConfettiArray[i].GetY(),ConfettiArray[i].GetWidth(),ConfettiArray[i].GetHeight(),ConfettiArray[i].GetColor(),ConfettiArray[i].GetRotationAngle());
}
}
var UpdateConfetti = function(modifier) {
for (i = 0; i < NUM_CONFETTI; i++) {
ConfettiArray[i].Update(modifier);
}
};
Firework = function(x, y, lineWidth, color, speedY, swayX, blastRadius) {
this.x = x;
this.y = y;
this.lineWidth = lineWidth;
this.color = color;
this.speedY = speedY;
this.swayX = swayX;
//this.rotationAngle = rotationAngle;
this.blastRadius = blastRadius;
};
Firework.prototype = {
Draw: function(x, y, lineWidth, color, speedY, swayX, blastRadius) {
context.fillStyle = color;
context.strokeStyle = color;
context.moveTo(x,y);
context.lineTo(x-swayX,y-speedY);
context.stroke();
},
GetX: function() {
return this.x;
},
GetY: function() {
return this.y;
},
GetLineWidth: function() {
return this.lineWidth;
},
GetColor: function() {
return this.color;
},
GetSpeedY: function() {
return this.speedY;
},
GetSwayX: function() {
return this.swayX;
},
GetRotationAngle: function() {
return this.rotationAngle;
},
GetBlastRadius: function() {
return this.blastRadius;
},
Update: function(modifier) {
this.x = this.x - this.swayX;
this.y = this.y - this.speedY;
if (this.y < -10) {this.x = GetRandom(0,canvas.width);this.y = canvas.height;this.speedY = GetRandom(30,100);this.swayX = GetRandom(-10,10)}
},
};
var DrawFireworks = function() {
//create confetti object array
for (i = 0; i < NUM_FIREWORKS; i++) {
FireworkArray[i].Draw(FireworkArray[i].GetX(), FireworkArray[i].GetY(), FireworkArray[i].GetLineWidth(), FireworkArray[i].GetColor(), FireworkArray[i].GetSpeedY(), FireworkArray[i].GetSwayX(), FireworkArray[i].GetBlastRadius());
}
};
var UpdateFireworks = function(modifier) {
for (i = 0; i < NUM_FIREWORKS; i++) {
FireworkArray[i].Update(modifier);
}
};
UncleSam = function() {
};
UncleSam.prototype = {
};
Text = function(context,title,x,y,color) {
this.context = context;
this.title = title;
this.x = x;
this.y = y;
this.color = color;
this.lineWidth = 2;
this.lineHeight =(this.context.measureText('W').width) + Math.pow((this.context.measureText('W').width),2);
this.font = '70pt Times New Roman';
//GET METRICS
this.metrics = this.context.measureText(this.title);
this.width = this.metrics.width;
this.maxWidth = canvas.width;
this.GradChangeSpeed = .5;
this.GradChangeOffset = .3;
this.debugCounter = 0;
};
Text.prototype = {
SetAttributes: function() {
context.font
context.textAlign = 'center'
context.font = this.font;
context.lineWidth = this.lineWidth;
context.lineHeight = this.GetHeight;
context.fillStyle = TextGradient;
context.strokeStyle = this.color;
//shadow attributes
context.shadowColor = undefined;
context.shadowOffsetX = 0;
context.shadowOffsetY = 0;
context.shadowBlur = 0;
},
//GETTTERS SETTERS///////////////////
GetTextX: function() {
return this.x;
},
GetTextY: function() {
return this.y;
},
GetTextLineHeight: function() {
return this.lineHeight;
},
GetTextWidth: function() {
return this.width;
},
//GETTERS SETTERS////////////
SetColorGradient: function() {
TextGradient.addColorStop(0,"red");
TextGradient.addColorStop(this.GradChangeOffset,"white");
TextGradient.addColorStop(.8,"blue");
},
Update: function(modifier) {
this.GradChangeOffset = this.GradChangeOffset + (this.GradChangeSpeed * modifier);
//GRADIENT DEBUGGERS
context.strokeText(this.GradChangeOffset.toFixed(2),canvas.width/2,canvas.height/2);
//GRADIENT DEBUGGERS
if (this.GradChangeOffset > .7 || this.GradChangeOffset < .2) {this.GradChangeSpeed = -(this.GradChangeSpeed);}
},
DrawText: function() {
this.WrapText(this.context, this.title, this.x, this.y, this.maxWidth, this.lineHeight);
},
WrapText: function(context, title, x, y, maxWidth, lineHeight) {
var words = title.split(' ');
var line = '';
for(var n = 0; n < words.length; n++) {
var testLine = line + words[n] + ' ';
var metrics = context.measureText(testLine);
var testWidth = metrics.width;
if (testWidth > maxWidth && n > 0) {
context.fillText(line, x, y);
context.strokeText(line, x, y);
line = words[n] + ' ';
y += lineHeight;
}
else {
line = testLine;
}
}
context.fillText(line, x, y);
context.strokeText(line, x, y);
},
};
//other functions
var ClearScreen = function() {
context.clearRect(0, 0, canvas.width, canvas.height);
};
var DrawObjects = function() {
ClearScreen();
Background1.DrawBackground();
Text1.SetAttributes();
Text1.SetColorGradient();
Text1.DrawText();
DrawFireworks();
DrawConfetti();
};
var UpdateObjects = function(modifier) {
//Text1.Update(modifier);
UpdateFireworks(modifier);
UpdateConfetti(modifier);
};
var Reset = function() {
};
//MAIN GAME LOOP FXN///////////////////
// The main game loop
var main = function() {
var now = Date.now();
var delta = now - then;
var frameRateAdjust = delta/1000;
DrawObjects(frameRateAdjust);
UpdateObjects(frameRateAdjust);
then = now;
//possibly do RESET
// Request to do this again ASAP
requestAnimationFrame(main);
};
// Cross-browser support for requestAnimationFrame
var w = window;
requestAnimationFrame = w.requestAnimationFrame || w.webkitRequestAnimationFrame || w.msRequestAnimationFrame || w.mozRequestAnimationFrame;
//START ECARD
//create variables
var then = Date.now();
var colorChoices = ["red","white","blue","deeppink","orange","limegreen","darkred"];
var NUM_CONFETTI = 25;
var NUM_FIREWORKS = 10;
var NUM_COLORS = colorChoices.length;
//create arrays for objects
var ConfettiArray = [];
var FireworkArray = [];
//create objects
Background1 = new Background(context,'black');
var Text1 = new Text(context,'Happy 4th of July!',canvas.width/2,canvas.height/10,'red');
var TextGradient = context.createLinearGradient(Text1.GetTextX(),Text1.GetTextY(),Text1.GetTextX()+Text1.GetTextWidth(),Text1.GetTextY()+Text1.GetTextLineHeight()/2)
//fill confetti object array
for (i = 0; i < NUM_CONFETTI; i++) {
ConfettiArray.push(new Confetti(GetRandom(0,canvas.width), GetRandom(-200,-10), GetRandom(10,30), GetRandom(10,30), colorChoices[GetRandom(0,NUM_COLORS)], GetRandom(0,2*Math.PI),GetRandom(50,80)));
}
//fill firework object array
for (i = 0; i < NUM_FIREWORKS; i++) {
FireworkArray.push(new Firework(GetRandom(0,canvas.width), canvas.height, GetRandom(4,20), colorChoices[GetRandom(0,NUM_COLORS)], GetRandom(30,100), GetRandom(-10,10), GetRandom(50,200)));
}
//start eCard animations
Reset();
main();

Begin a new path with ctx.beginPath()
The reason is because you are creating one path out of all the firework lines.
//firework.draw
Draw: function(x, y, lineWidth, color, speedY, swayX, blastRadius) {
context.fillStyle = color;
context.strokeStyle = color; // sets the stroke color
context.moveTo(x,y); // adds another line
context.lineTo(x-swayX,y-speedY);
context.stroke(); // stroke all lines up to this point
},
Each time stroke is called all the firework lines are render up to that point.
The result is that the last stroke call draws all the lines again the color of the last firework.
The fix
The fix is simple. Just start a new path with ctx.beginPath()
//firework.draw
Draw: function(x, y, lineWidth, color, speedY, swayX, blastRadius) {
context.fillStyle = color;
context.strokeStyle = color; // sets the stroke color
//========================================================
context.beginPath(); // start a new path
//========================================================
context.moveTo(x,y);
context.lineTo(x-swayX,y-speedY);
context.stroke();
},