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How to use L.canvas to draw a fluctuating circle

I am a back-end programmer who is using leaflet for the first time. I don’t know much about js animation steps. I want to use L.canvas to draw a dynamic circle, just like the picture below.
Specify the range of the circle or the latitude and longitude of the center of the circle, and the radius will continue to fluctuate and spread outward, similar to water waves (this effect in the picture is made by me using a highly encapsulated animation library)
I hope someone can provide me with an example, or give me a suggestion so that I can smoothly draw a dynamic circle on the map. thanks a lot

You can create mutliple circles and update the radius each millisecond:
var canvasRenderer = L.canvas();
function createWavingCircle(latlng, color, fromRadius, toRadius){
var circle = L.circle(latlng, {radius: fromRadius, color, renderer: canvasRenderer}).addTo(map);
var nextCircle;
var interval = setInterval(()=>{
var radius = circle.getRadius()+1;
if(radius <= toRadius){
circle.setRadius(radius);
if(Math.round((radius / toRadius) * 100) >= 30 && !nextCircle){
nextCircle = createWavingCircle(latlng, color, fromRadius, toRadius);
}
} else {
if(nextCircle && nextCircle.getRadius() >= toRadius){
circle.remove();
clearInterval(interval);
}
}
},1)
return circle;
}
// replace this values with your custom ones
createWavingCircle(map.getCenter(), 'red', 10, 400);
https://plnkr.co/edit/IT5VcxokeCWpkpEx

Create a new L.canvas object and specify the desired options, and use the addTo() method to add the circle to your map.
This will create a circle that is initially drawn with a radius of 10, and will have its radius redrawn with a new random value every second. The circle will continue to fluctuate in size until the setInterval() loop is stopped.
import { L } from 'leaflet';
const circle = L.canvas({
center: [51.505, -0.09],
radius: 10,
color: 'red',
});
circle.addTo(map);
setInterval(() => {
const newRadius = Math.random() * 50;
circle.setRadius(newRadius);
}, 1000);
Hope it works!

// build CircleMarker
createFloatCircle(latLng, color, fromRadius, toRadius){
var _this = this;
var circle = L.circleMarker(latLng,
{radius: fromRadius,
color: color,
renderer: L.canvas({ padding: 0.5 }),
fillColor: color,
fillOpacity: 0.5,
stroke: false,
});
circle.addTo(_this.offMap);
setInterval(() => {
var newRadius = circle.getRadius() + 1;
if(newRadius <= toRadius){
circle.setRadius(newRadius);
} else {
circle.setRadius(fromRadius);
}
circle.setStyle({fillColor: _this.getColor(newRadius, fromRadius, toRadius)});
}, 20);
},
getColor(radius, fromRadius, toRadius){
var _this = this;
var color = 'red';
var percent = (radius - fromRadius) / (toRadius - fromRadius);
var red = Math.round(255 * percent);
var green = Math.round(255 * (1 - percent));
color = 'rgb(' + red + ',' + green + ',0)';
return color;
},
This is my implementation, as the circle expands, the color of the layer gradually deepens

Limit dragged line to an arc / radius of a given length

I'm currently using Phaser 3, although my question isn't technically restricted to that framework, as it's more of a general JS/canvas/maths question, but:
I have a line drawn with graphics(). It’s anchored at one end, and the other end is draggable. I made a quick demo and so far, so good - you can see what I have already on CodePen.
Dragging the marker around and redrawing the line is no problem, but what I’d like is for that line to have a maximum length of 100, so even if you’re still dragging beyond that point, the line would still follow the mouse, but not get any longer than 100. Dragging inside that maximum radius, the line would shrink as normal.
I’ve put together a visual that hopefully explains it:
The issue is that I suspect this is VERY MATHS and I am very, very weak with maths. Could anyone explain like I’m five what I need to do to my code to achieve this?
Edit: Adding code in a snippet here, as requested:
var config = {
type: Phaser.AUTO,
width: 800,
height: 400,
backgroundColor: '#2d2d2d',
parent: 'phaser-example',
scene: {
preload: preload,
create: create,
update: update
}
};
var path;
var curve;
var graphics;
var game = new Phaser.Game(config);
function preload() {
this.load.spritesheet('dragcircle', 'https://labs.phaser.io/assets/sprites/dragcircle.png', { frameWidth: 16 });
}
function create() {
graphics = this.add.graphics();
path = { t: 0, vec: new Phaser.Math.Vector2() };
curve = new Phaser.Curves.Line([ 400, 390, 300, 230 ]);
var point0 = this.add.image(curve.p0.x, curve.p0.y, 'dragcircle', 0);
var point1 = this.add.image(curve.p1.x, curve.p1.y, 'dragcircle', 0).setInteractive();
point1.setData('vector', curve.p1);
this.input.setDraggable(point1);
this.input.on('drag', function (pointer, gameObject, dragX, dragY) {
gameObject.x = dragX;
gameObject.y = dragY;
gameObject.data.get('vector').set(dragX, dragY);
});
this.input.on('dragend', function (pointer, gameObject) {
let distance = Phaser.Math.Distance.Between(curve.p0.x, curve.p0.y, curve.p1.x, curve.p1.y);
console.log(distance);
});
}
function update() {
graphics.clear();
graphics.lineStyle(2, 0xffffff, 1);
curve.draw(graphics);
curve.getPoint(path.t, path.vec);
}
<script src="https://cdnjs.cloudflare.com/ajax/libs/phaser/3.55.2/phaser.min.js"></script>

You are right, you would need some math, but phaser has many helper functions, that will do the heavy lifting.
The main idea is, of this solution is
define a maxLength
get the the new point on drag, and create a real Phaser Vector2
here is some math is needed, to create the vector, just calculate destination point minus origin point
new Phaser.Math.Vector2(pointer.x - point0.x, pointer.y - point0.y) (origin point being the starting point of the desired vector, and destination point being the mouse pointer)
calculate the length of the created vector and compare it with the maxLength
if too long adjust the vector, with the handy function setLength (link to the documentation, this is where you would have needed math, but thankfully Phaser does it for us)
set the new coordinates for point1 and the curve endpoint
Here a quick demo (based on your code):
var config = {
type: Phaser.AUTO,
width: 500,
height: 170,
scene: {
preload: preload,
create: create,
update: update
}
};
var curve;
var graphics;
var game = new Phaser.Game(config);
function preload() {
this.load.spritesheet('dragcircle', 'https://labs.phaser.io/assets/sprites/dragcircle.png', { frameWidth: 16 });
}
function create() {
graphics = this.add.graphics();
curve = new Phaser.Curves.Line([ config.width/2, config.height - 20, config.width/2, 10 ]);
// define a length, could be a global constant
let maxLength = curve.p0.y - curve.p1.y;
var point0 = this.add.image(curve.p0.x, curve.p0.y, 'dragcircle', 0);
var point1 = this.add.image(curve.p1.x, curve.p1.y, 'dragcircle', 0).setInteractive();
this.input.setDraggable(point1);
// Just add for Debug Info
this.add.circle(curve.p0.x, curve.p0.y, maxLength)
.setStrokeStyle(1, 0xffffff, .5)
this.input.on('drag', function (pointer) {
let vector = new Phaser.Math.Vector2(pointer.x - point0.x, pointer.y - point0.y);
let distance = Phaser.Math.Distance.Between( point0.x, point0.y, pointer.x, pointer.y);
if(distance > maxLength){
vector.setLength(maxLength);
}
point1.x = point0.x + vector.x;
point1.y = point0.y + vector.y;
curve.p1.x = point1.x;
curve.p1.y = point1.y;
});
// NOT REALLY NEEDED
/*this.input.on('dragend', function (pointer, gameObject) {
let distance = Phaser.Math.Distance.Between(curve.p0.x, curve.p0.y, curve.p1.x, curve.p1.y);
console.log(distance);
});*/
}
function update() {
graphics.clear();
graphics.lineStyle(2, 0xffffff, 1);
curve.draw(graphics);
}
<script src="https://cdn.jsdelivr.net/npm/phaser#3.55.2/dist/phaser.js"></script>
Optional - Code Version using Phaser.GameObjects.Line:
This uses less code, and thanks to the Line GameObject (link to Documentation), you can directly use the vector to update the line, and also don't need the update function, graphics and so.
const config = {
type: Phaser.CANVAS,
width: 500,
height: 160,
scene: {
create
}
};
const game = new Phaser.Game(config);
const MAX_LINE_LENGTH = 100;
function create() {
let points = [ {x: config.width/2, y: config.height - 20}, {x: config.width/2, y: config.height - 120} ];
let point0 = this.add.circle(points[0].x, points[0].y, 6)
.setStrokeStyle(4, 0xff0000);
let point1 = this.add.circle(points[1].x, points[1].y, 6)
.setStrokeStyle(4, 0xff0000)
.setInteractive();
this.input.setDraggable(point1);
// Just add for Debug Info
this.add.circle(point0.x, point0.y, MAX_LINE_LENGTH)
.setStrokeStyle(1, 0xffffff, .5);
let line = this.add.line(points[0].x, points[0].y, 0, 0, 0, -100, 0x00ff00)
.setOrigin(0);
this.input.on('drag', function (pointer) {
let vector = new Phaser.Math.Vector2(pointer.x - point0.x, pointer.y - point0.y);
let distance = Phaser.Math.Distance.Between( point0.x, point0.y, pointer.x, pointer.y);
if(distance > MAX_LINE_LENGTH){
vector.setLength(MAX_LINE_LENGTH);
}
point1.x = point0.x + vector.x;
point1.y = point0.y + vector.y;
line.setTo(0, 0, vector.x, vector.y);
});
}
<script src="//cdn.jsdelivr.net/npm/phaser#3.55.2/dist/phaser.js"></script>

Is there a way to resize a circle by dragging the circumference outward / inward using Konva js?

Using Konva js, Is there a way to drag a circle's circumference without showing the resizers elements, in order to resize the circle ( make the radius grow)?
Using a Transformer - displays the resizers, and stretches rectangles by changing the scale. I want to actually resize the circle (larger radius) without showing the resizers.
All help will be appreciated. Thx

You may need to use two circles for that. One circle is your main shape, another circle for detecting events on stroke (the second circle can be transparent if you don't want to see it on the screen).
const stage = new Konva.Stage({
container: 'container',
width: window.innerWidth,
height: window.innerHeight
});
const layer = new Konva.Layer();
stage.add(layer);
const circle = new Konva.Circle({
x: stage.width() / 2,
y: stage.height() / 2,
radius: 50,
fill: 'green'
});
layer.add(circle);
const border = new Konva.Circle({
x: stage.width() / 2,
y: stage.height() / 2,
radius: 50,
stroke: 'black',
strokeWidth: 6,
fillEnabled: false
});
layer.add(border);
function distance(p1, p2) {
return Math.sqrt(Math.pow(p1.x - p2.x, 2) + Math.pow(p1.y - p2.y, 2));
}
border.on('mouseenter', () => {
border.stroke('red');
layer.batchDraw();
})
border.on('mouseleave', () => {
border.stroke('black');
layer.batchDraw();
})
border.on('mousedown', () => {
// attach move event
stage.on('mousemove.resizer', () => {
const center = border.position();
const pointer = stage.getPointerPosition();
const radius = distance(center, pointer);
border.radius(radius);
circle.radius(radius)
layer.batchDraw();
});
// remove all events at end
stage.on('mouseup.resizer', () => {
stage.off('.resizer')
});
})
layer.draw();
<script src="https://unpkg.com/konva#^2/konva.min.js"></script>
<div id="container"></div>

Animating multiple items in Paper.js while anchored to a path

I have five rectangles placed at different points along a circle like this - http://imgur.com/uVYkwl7.
Upon clicking any rectangle i want the circle to move to the left of the screen, gradually scaling down it's radius until the circle's center reaches x=0. I'd like the five rectangles to move along with the circle while its being scaled down and also adjust their own positions and scale on the circle so that they are within the view's bounds, like this - http://imgur.com/acDG0Aw
I'd appreciate any help on how to go about doing this. Heres my code for getting to the 1st image and animating the circle:
var radius = 300;
var center = view.center;
var circle = new Path.Circle({
center: view.center,
radius: radius,
strokeColor: 'black',
name: 'circle'
});
var path = new Path.Rectangle({
size: [230, 100],
fillColor: '#1565C0'
});
var rectText = ['Text 1',
'Text 2',
'Text 3',
'Text 4',
'Text 5'
];
var symbol = new Symbol(path);
var corners = [
new Point(center.x, center.y - radius),
new Point(center.x - radius, center.y - radius / 2),
new Point(center.x + radius, center.y - radius / 2),
new Point(center.x - radius, center.y + radius / 2),
new Point(center.x + radius, center.y + radius / 2)
];
var rectClicked = false;
var clickedRect = null;
var rectClick = function(event) {
rectClicked = true;
clickedRect = this;
};
function onFrame(event) {
// Your animation code goes in here
if (rectClicked) {
for (var i = 0; i < 1; i++) {
var item = project.activeLayer.children[i];
if (item.name == 'circle') {
if (item.position.x < 0) {
rectClicked = false;
} else {
item.position.x -= 10;
item.scale(1/1.01);
}
}
}
}
}
// Place the instances of the symbol:
for (var i = 0; i < corners.length; i++) {
var placedSymbol = symbol.place(corners[i]);
placedSymbol.onMouseDown = rectClick;
var rText = new PointText({
point: placedSymbol.bounds.topLeft + 20,
content: rectText[i],
fontSize: '20',
fillColor: 'white'
});
}

Paper.js provides rotations around a pivot out of the box.
var pivotPoint = new Point(10, 5);
circle.rotate(30,pivotPoint);
Here is the docs reference for this behaviour and here is a very basic Sketch example to illustrate this
The above snippet will rotate a circle(you can change this to rectangle in your case) by 30 degrees around a pivot point at coordinates 10,5 on the x/y axis.
Thus what you describe is certainly doable as long as the path that your elements will follow is always circular.
Bear in mind that in order for the pivot rotation to work the way you want them to you need to update the pivotPoint and reinitiate the rotation again.
Note: In case you want to move along an arbitrary shape instead of circular path, you should search for Paper.js animation-along-a-path which is something that I've seen been done before without much difficulty - e.g this simple Sketch by the creator of Paper.js himself.
The sketch I provided above is a basic example of rotation around a pivot point.
I'm dumping the Sketch code here in case the link goes dead:
//Create a center point
var centerCircle = new Path.Circle(paper.view.center, 100);
centerCircle.strokeColor = 'black';
centerCircle.dashArray = [10, 12];
//Create the circles
var circle1Radius = 30;
var circle1 = new Path.Circle((centerCircle.position-centerCircle.bounds.width/2)+circle1Radius, circle1Radius);
circle1.fillColor = '#2196F3';
var circle2Radius = 40;
var circle2 = new Path.Circle((centerCircle.position-centerCircle.bounds.width/2)+circle2Radius, circle2Radius);
circle2.fillColor = '#E91E63';
var circle3Radius = 40;
var circle3 = new Path.Circle((centerCircle.position-centerCircle.bounds.width/2)+circle2Radius, circle2Radius);
circle3.fillColor = '#009688';
var i=0;
var animationGap = 125; //how long to move before animating the next circle
var rotationSpeed = 2;
function onFrame(event) {
circle1.rotate(rotationSpeed,centerCircle.position);
if(i>animationGap)
circle2.rotate(rotationSpeed,centerCircle.position);
if(i>animationGap*2)
circle3.rotate(rotationSpeed,centerCircle.position);
i++;
}

animation path problems

How would I make my object reach the end of the animation paths? I am making a basic pong game, but the ball stops early if it misses the paddle, It should reach the end of the path. Here is my code:
<!DOCTYPE html>
<html>
<head>
<meta http-equiv="content-type" content="text/html; charset=utf8">
<title> Rapahel test </title>
<script type="text/javascript" src="raphael.js">
</script>
</head>
<body>
<script type="text/javascript">
//create the canvas, which all the shapes are on
var paper = Raphael(0,0,500,500);
ballpath = '';
ballNum = 0;
//the paths the ball will follow, one at a time, starting from 0. which is the first in an array.
paths = ["M480, 180L35, 180", "M35, 180L480, 325", "M480, 325L35, 110", "M35, 110L480, 50", "M480, 50L35, 340", "M35, 340L480, 340", "M480, 340L35, 200", "M35, 200L35, 200"];
Raphael(function () {
ballpath = paper.path(paths[ballNum]).attr({stroke: "#0000ff", opacity: .3, "stroke-width": 1});
var ball = paper.circle(0, 0, 5).attr("fill", "rgba(255, 0, 0, 1)");
//the length variable (and arribute)
var len = ballpath.getTotalLength();
ball.onAnimation(function () {
var t = this.attr("transform");
});
paper.customAttributes.along = function (v) {
var point = ballpath.getPointAtLength(v * len);
return {
transform: "t" + [point.x, point.y] + "r" + point.alpha
};
};
ball.attr({along: 0});
//the variable rotateAlongThePath is true
var rotateAlongThePath = true;
//th function that actually makes the ball move
function run() {
//the path which the wall will follow
wallpath = paper.path("M480, 180L480, 380, M480, 380L480, 60, M480, 60L480, 340").attr({stroke: "#0000ff", opacity: .3, "stroke-width": 1});
//create a rectangle
var wall2 = paper.rect(0 - 50, 0 - 9, 100, 20).attr("fill", "rgba(0, 0, 255, 1)");
//the length variable (and arribute)
var wallLen = wallpath.getTotalLength();
//not sure aout these commands, they are to do with animation paths
wall2.onAnimation(function () {
var t = this.attr("transform");
});
paper.customAttributes.along2 = function (v2) {
var point2 = wallpath.getPointAtLength(v2 * wallLen);
return {
transform: "t" + [point2.x, point2.y] + "r" + point2.alpha
};
};
//set the wall's movemnt to 0
wall2.attr({along2: 0});
var collision = function(){
//find the paddle's height and width, the ball's center point, and AI Paddle's x position
var paddleheight = Math.round(paddle.getBBox().y + paddle.getBBox().height / 2);
var paddleWidth = Math.round(paddle.getBBox().x + paddle.getBBox().width / 2);
var ballcenterpoint = Math.round(ball.getBBox().y + ball.getBBox().height / 2);
var AIpaddle = Math.round(wall2.getBBox().x + wall2.getBBox().width / 2);
//the height from the center point of the paddle to the edge (heigh variance), finding the height of the top edge of the boundingbox (where the ball will colide with) by adding the centerpoint and height variance. finding the bottom edge by subtracting the centerpoint from the bounding box.
var heightvariance = pHeight;
var heightPlusboundingbox = paddleheight + heightvariance;
var heightMinusboundingbox = paddleheight - heightvariance;
//if the edge of the box is less than or equal to the center of the ball.
var balledge = Math.round(ball.getBBox().x + (ball.getBBox().width / 2) + 22);
//continue ballbounce is used for the if below; it equals: if the ball center is largerthan or equal to the height of the paddle minus its bounding box AND the center point is equal to or less than the height of the paddle plus the bounding box AND the center is equal to or greater than the width (extending the detected edge ofthe box by a few pixels so as to fix some collision problems) the if below will work.
console.log('Ball X: ', balledge);
console.log('AI X: ', AIpaddle);
console.log(balledge);
console.log(AIpaddle);
//the if
if(ballcenterpoint >= heightMinusboundingbox && ballcenterpoint <= heightPlusboundingbox || balledge >= AIpaddle){
//if the ball number is less than or equal to 6 it will increase theball number by one an change the ballpath to one in the array called paths[ballNum], the ball will then begin at the beginning of that path and be animated along it
if(ballNum <= 6){
ballNum++
ballpath = paper.path(paths[ballNum]).attr({stroke: "#0000ff", opacity: .3, "stroke-width": 1});
ball.attr({along: 0});
ball.animate({along: 1}, 2500, onanimationdone);
}
//if the ballNum is greater than 6 it will remove the ball (fixin the error of an infinite loop of theball just sitting the corner acting all boring and doing nothing)
}
else {
// ball.remove(); //- YOU LOSE
};
};
//animates the wall
wall2.animate({along2: 1}, 16200, function () {
});
//loops through all the ball paths
var onanimationdone = function () {
collision();
};
ball.animate({along: 1}, 2500, onanimationdone);
ball.attr({along: 0});
};
//create a rectangles
var pHeight = 100;
var pWidth = 20;
var paddle = paper.rect(10, 130, pWidth, pHeight);
paddle.attr("fill", "rgba(0, 0, 255, 1)");
var start = function () {
// storing original coordinates
this.originalY = this.attr("y");
this.attr({opacity: 0.9});
},
move = function (dx, dy) {
// moves the object up and down, when clicked and dragged
this.attr({y: this.originalY + dy});
},
up = function () {
// restoring state
this.attr({opacity: 1.0});
};
//runs the functions
paddle.drag(move, start, up);
run();
});
</script>
</body
</html>
I am new to JavaScript, I apologise if my code is a little hard to understand (this is my fourth day doing JavaScript).

Using raphael is valid for rendering your graphics, but I would suggest using the paths array for the ball's motion is not. If you are in fact trying to make a game you are best off having the ball store it's current position and velocity, and update these per frame via some some of timer.