Move rects in canvas at the same time - javascript

I have created multiple rectangles in the Canvas element. The primary goal is to move all of them in the direction of the touch or mouse move event. Maybe the answer is in front of me, but right now I am blind :(
Here is the example code on plunker
Code:
var context = {
collection: [],
canvas: document.getElementById('canvas'),
ctx: canvas.getContext('2d'),
isMoving: false
};
for (let f = 0; f < 3; f++) {
var item = {
x: (Math.random() * 200),
y: (Math.random() * 100),
w: 50,
h: 50
};
context.collection.push(item);
}
drawAll(context);
Touch event handler:
context.canvas.addEventListener("mousedown", function (e) { onTouchHandler(e, context) }, false)
context.canvas.addEventListener("mousemove", function (e) { onTouchHandler(e, context) }, false);
context.canvas.addEventListener("mouseup", function (e) { onTouchHandler(e, context) }, false);
function onTouchHandler(e, context) {
var touch = getTouchCoordinates(e.pageX, e.pageY, context.canvas);
switch (e.type) {
case 'mousedown':
context.isMoving = true;
break;
case 'mousemove':
if(context.isMoving === true){
console.log(touch);
//TODO: move all objects by the cursor...
for (let f = 0; f < context.collection.length; f++) {
var item = context.collection[f];
}
//drawAll(context);
}
break;
case 'mouseup':
context.isMoving = false;
break;
default:
break;
}
}
Draw rectangles:
function drawAll(context){
var canvas = context.canvas,
ctx = context.ctx,
shapes = context.collection;
clearAll(ctx, canvas);
for (let x = 0; x < shapes.length; x++) {
var element = shapes[x];
ctx.rect(element.x, element.y, element.w, element.h);
ctx.stroke();
}
}
Clear rects:
function clearAll(ctx, canvas){
ctx.clearRect(0, 0, canvas.width, canvas.height);
}
Get touch x,y:
function getTouchCoordinates(pageX, pageY, canvas) {
var element = canvas,
offsetX = 0,
offsetY = 0,
currentX,
currentY;
if (element.offsetParent != undefined) {
do {
offsetX += element.offsetLeft;
offsetY += element.offsetTop;
} while ((element = element.offsetParent))
}
currentX = pageX - offsetX;
currentY = pageY - offsetY;
return {
x: currentX,
y: currentY
}
}

I've simplified your code a bit just to show how you could move the rectangles. I'm not checking for mouse press or release.
var context = {
collection: [],
canvas: document.getElementById('canvas'),
ctx: canvas.getContext('2d'),
isMoving: false
};
// rectangle positions
for (let f = 0; f < 3; f++) {
var item = {
x: (Math.random() * 200),
y: (Math.random() * 100),
w: 50,
h: 50
};
context.collection.push(item);
}
// listen
context.canvas.addEventListener("mousemove", (e) => onMoveHandler(e));
// Draw
drawAll();
function onMoveHandler(e) {
//console.log(e.clientX, e.clientY)
for (let f = 0; f < context.collection.length; f++) {
var item = context.collection[f];
var xdifference = item.x - e.pageX
item.x = (xdifference < 0) ? item.x + 1 : item.x -1
var ydifference = item.y - e.pageY
item.y = (ydifference < 0) ? item.y + 1 : item.y -1
}
drawAll()
}
function drawAll(){
// clear all
clearAll();
for (let x = 0; x < context.collection.length; x++) {
var element = context.collection[x];
context.ctx.rect(element.x, element.y, element.w, element.h);
context.ctx.stroke();
}
}
function clearAll(){
context.ctx.clearRect(0, 0, context.canvas.width, context.canvas.height);
}
If you want a more "natural" looking movement towards the mouse, you can calculate the x and y difference using the Pythagorean theorem:
var xdifference = e.pageX - item.x
var ydifference = e.pageY - item.y
let distance = Math.sqrt(xdifference * xdifference + ydifference * ydifference)
item.x += (xdifference / distance)
item.y += (ydifference / distance)
In the plunker example it's not 100% accurate because the x,y offset of the element on the page isn't used in the calculation :)

I figured out the answer.
"mousedown" - used to store initial x,y of the mouse
"mousemove" - used to move whole canvas section just to simulate the movement of the rectangles and store offset (x,y)
"mouseup" - the key point is to use the stored offset (x,y) and set the positions of the rectangles, after that reset canvas position and redraw rectangles with new values.
Maybe there is more elegant way to do it, but right now this will do the trick :)

Related

Javascript - interactive particle logo not working

I'm working through instructions to construct an interactive particle logo design and can't seem to get to the finished product. This is the logo image file -
I'm using a canvas structure / background. Here's the code -
var canvasInteractive = document.getElementById('canvas-interactive');
var canvasReference = document.getElementById('canvas-reference');
var contextInteractive = canvasInteractive.getContext('2d');
var contextReference = canvasReference.getContext('2d');
var image = document.getElementById('img');
var width = canvasInteractive.width = canvasReference.width = window.innerWidth;
var height = canvasInteractive.height = canvasReference.height = window.innerHeight;
var logoDimensions = {
x: 500,
y: 500
};
var center = {
x: width / 2,
y: height / 2
};
var logoLocation = {
x: center.x - logoDimensions.x / 2,
y: center.y - logoDimensions.y / 2
};
var mouse = {
radius: Math.pow(100, 2),
x: 0,
y: 0
};
var particleArr = [];
var particleAttributes = {
friction: 0.95,
ease: 0.19,
spacing: 6,
size: 4,
color: "#ffffff"
};
function Particle(x, y) {
this.x = this.originX = x;
this.y = this.originY = y;
this.rx = 0;
this.ry = 0;
this.vx = 0;
this.vy = 0;
this.force = 0;
this.angle = 0;
this.distance = 0;
}
Particle.prototype.update = function() {
this.rx = mouse.x - this.x;
this.ry = mouse.y - this.y;
this.distance = this.rx * this.rx + this.ry * this.ry;
this.force = -mouse.radius / this.distance;
if (this.distance < mouse.radius) {
this.angle = Math.atan2(this.ry, this.rx);
this.vx += this.force * Math.cos(this.angle);
this.vy += this.force * Math.sin(this.angle);
}
this.x += (this.vx *= particleAttributes.friction) + (this.originX - this.x) * particleAttributes.ease;
this.y += (this.vy *= particleAttributes.friction) + (this.originY - this.y) * particleAttributes.ease;
};
function init() {
contextReference.drawImage(image, logoLocation.x, logoLocation.y);
var pixels = contextReference.getImageData(0, 0, width, height).data;
var index;
for (var y = 0; y < height; y += particleAttributes.spacing) {
for (var x = 0; x < width; x += particleAttributes.spacing) {
index = (y * width + x) * 4;
if (pixels[++index] > 0) {
particleArr.push(new Particle(x, y));
}
}
}
};
init();
function update() {
for (var i = 0; i < particleArr.length; i++) {
var p = particleArr[i];
p.update();
}
};
function render() {
contextInteractive.clearRect(0, 0, width, height);
for (var i = 0; i < particleArr.length; i++) {
var p = particleArr[i];
contextInteractive.fillStyle = particleAttributes.color;
contextInteractive.fillRect(p.x, p.y, particleAttributes.size, particleAttributes.size);
}
};
function animate() {
update();
render();
requestAnimationFrame(animate);
}
animate();
document.body.addEventListener("mousemove", function(event) {
mouse.x = event.clientX;
mouse.y = event.clientY;
});
document.body.addEventListener("touchstart", function(event) {
mouse.x = event.changedTouches[0].clientX;
mouse.y = event.changedTouches[0].clientY;
}, false);
document.body.addEventListener("touchmove", function(event) {
event.preventDefault();
mouse.x = event.targetTouches[0].clientX;
mouse.y = event.targetTouches[0].clientY;
}, false);
document.body.addEventListener("touchend", function(event) {
event.preventDefault();
mouse.x = 0;
mouse.y = 0;
}, false);
html,
body {
margin: 0px;
position: relative;
background-color: #000;
}
canvas {
display: block;
position: absolute;
top: 0;
left: 0;
z-index: 1;
}
img {
display: none;
width: 70%;
height: 400px;
position: absolute;
left: 50%;
transform: translate(-50%, 30%);
}
<html>
<body>
<canvas id="canvas-interactive"></canvas>
<canvas id="canvas-reference"></canvas>
<img src="https://i.stack.imgur.com/duv9h.png" alt="..." id="img">
</body>
</html>
My understanding is the image file has to be set to display: none; and then the image needs to be re-drawn using the javascript commands but I'm not sure if this image is compatible or not. When finished I want the image on a white background.
By way of an example the end design needs to resemble this - Logo particle design
Particle positions from bitmap.
To get the FX you want you need to create a particle system. This is just an array of objects, each with a position, the position where they want to be (Home), a vector defining their current movement, and the colour.
You get each particle's home position and colour by reading pixels from the image. You can access pixel data by rendering an image on a canvas and the using ctx.getImageData to get the pixel data (Note image must be on same domain or have CORS headers to access pixel data). As you read each pixel in turn, if not transparent, create a particle for that pixel and set it colour and home position from the pixels colour and position.
Use requestAnimationFrame to call a render function that every frame iterates all the particles moving them by some set of rules that give you the motion you are after. Once you have move each particle, render them to the canvas using simple shapes eg fillRect
Mouse interaction
To have interaction with the mouse you will need to use mouse move events to keep track of the mouse position relative to the canvas you are rendering to. As you update each particle you also check how far it is from the mouse. You can then push or pull the particle from or to the mouse (depending on the effect you want.
Rendering speed will limit the particle count.
The only issue with these types of FX is that you will be pushing the rendering speed limits as the particle count goes up. What may work well on one machine, will run very slow on another.
To avoid being too slow, and not looking good on some machines you should consider keeping an eye on the frame rate and reducing the particle count if it runs slow. To compensate you can increase the particle size or even reduce the canvas resolution.
The bottleneck is the actual rendering of each particle. When you get to large numbers the path methods really grinds down. If you want really high numbers you will have to render pixels directly to the bitmap, using the same method as reading but in reverse of course.
Example simple particles read from bitmap.
The example below uses text rendered to a canvas to create the particles, and to use an image you would just draw the image rather than the text. The example is a bit overkill as I ripped it from an old answer of mine. It is just as an example of the various ways to get stuff done.
const ctx = canvas.getContext("2d");
const Vec = (x, y) => ({x, y});
const setStyle = (ctx,style) => { Object.keys(style).forEach(key => ctx[key] = style[key]) }
const createImage = (w,h) => {var i=document.createElement("canvas");i.width=w;i.height=h;i.ctx=i.getContext("2d");return i}
const textList = ["Particles"];
var textPos = 0;
var w = canvas.width;
var h = canvas.height;
var cw = w / 2; // center
var ch = h / 2;
var globalTime;
var started = false;
requestAnimationFrame(update);
const mouse = {x : 0, y : 0, button : false}
function mouseEvents(e){
mouse.x = e.pageX;
mouse.y = e.pageY;
mouse.button = e.type === "mousedown" ? true : e.type === "mouseup" ? false : mouse.button;
}
["down","up","move"].forEach(name => document.addEventListener("mouse"+name,mouseEvents));
function onResize(){
cw = (w = canvas.width = innerWidth) / 2;
ch = (h = canvas.height = innerHeight) / 2;
if (!started) { startIt() }
}
function update(timer){
globalTime = timer;
ctx.setTransform(1,0,0,1,0,0); // reset transform
ctx.globalAlpha = 1; // reset alpha
if (w !== innerWidth || h !== innerHeight){ onResize() }
else { ctx.clearRect(0,0,w,h) }
particles.update();
particles.draw();
requestAnimationFrame(update);
}
function createParticles(text){
createTextMap(
text, 60, "Arial",
{ fillStyle : "#FF0", strokeStyle : "#F00", lineWidth : 2, lineJoin : "round", },
{ top : 0, left : 0, width : canvas.width, height : canvas.height }
)
}
// This function starts the animations
function startIt(){
started = true;
const next = ()=>{
var text = textList[(textPos++ ) % textList.length];
createParticles(text);
setTimeout(moveOut,text.length * 100 + 12000);
}
const moveOut = ()=>{
particles.moveOut();
setTimeout(next,2000);
}
setTimeout(next,0);
}
// the following function create the particles from text using a canvas
// the canvas used is displayed on the main canvas top left fro reference.
var tCan = createImage(100, 100); // canvas used to draw text
function createTextMap(text,size,font,style,fit){
const hex = (v)=> (v < 16 ? "0" : "") + v.toString(16);
tCan.ctx.font = size + "px " + font;
var width = Math.ceil(tCan.ctx.measureText(text).width + size);
tCan.width = width;
tCan.height = Math.ceil(size *1.2);
var c = tCan.ctx;
c.font = size + "px " + font;
c.textAlign = "center";
c.textBaseline = "middle";
setStyle(c,style);
if (style.strokeStyle) { c.strokeText(text, width / 2, tCan.height / 2) }
if (style.fillStyle) { c.fillText(text, width / 2, tCan.height/ 2) }
particles.empty();
var data = c.getImageData(0,0,width,tCan.height).data;
var x,y,ind,rgb,a;
for(y = 0; y < tCan.height; y += 1){
for(x = 0; x < width; x += 1){
ind = (y * width + x) << 2; // << 2 is equiv to * 4
if(data[ind + 3] > 128){ // is alpha above half
rgb = `#${hex(data[ind ++])}${hex(data[ind ++])}${hex(data[ind ++])}`;
particles.add(Vec(x, y), Vec(x, y), rgb);
}
}
}
particles.sortByCol
var scale = Math.min(fit.width / width, fit.height / tCan.height);
particles.each(p=>{
p.home.x = ((fit.left + fit.width) / 2) + (p.home.x - (width / 2)) * scale;
p.home.y = ((fit.top + fit.height) / 2) + (p.home.y - (tCan.height / 2)) * scale;
})
.findCenter() // get center used to move particles on and off of screen
.moveOffscreen() // moves particles off the screen
.moveIn(); // set the particles to move into view.
}
// basic particle
const particle = { pos : null, delta : null, home : null, col : "black", }
// array of particles
const particles = {
items : [], // actual array of particles
mouseFX : { power : 12,dist :110, curve : 2, on : true },
fx : { speed : 0.3, drag : 0.6, size : 4, jiggle : 1 },
// direction 1 move in -1 move out
direction : 1,
moveOut () {this.direction = -1; return this},
moveIn () {this.direction = 1; return this},
length : 0,
each(callback){ // custom iteration
for(var i = 0; i < this.length; i++){ callback(this.items[i],i) }
return this;
},
empty() { this.length = 0; return this },
deRef(){ this.items.length = 0; this.length = 0 },
sortByCol() { this.items.sort((a,b) => a.col === b.col ? 0 : a.col < b.col ? 1 : -1 ) },
add(pos, home, col){ // adds a particle
var p;
if(this.length < this.items.length){
p = this.items[this.length++];
p.home.x = home.x;
p.home.y = home.y;
p.delta.x = 0;
p.delta.y = 0;
p.col = col;
}else{
this.items.push( Object.assign({}, particle,{ pos, home, col, delta : Vec(0,0) } ) );
this.length = this.items.length
}
return this;
},
draw(){ // draws all
var p, size, sizeh;
sizeh = (size = this.fx.size) / 2;
for(var i = 0; i < this.length; i++){
p = this.items[i];
ctx.fillStyle = p.col;
ctx.fillRect(p.pos.x - sizeh, p.pos.y - sizeh, size, size);
}
},
update(){ // update all particles
var p,x,y,d;
const mP = this.mouseFX.power;
const mD = this.mouseFX.dist;
const mC = this.mouseFX.curve;
const fxJ = this.fx.jiggle;
const fxD = this.fx.drag;
const fxS = this.fx.speed;
for(var i = 0; i < this.length; i++){
p = this.items[i];
p.delta.x += (p.home.x - p.pos.x ) * fxS + (Math.random() - 0.5) * fxJ;
p.delta.y += (p.home.y - p.pos.y ) * fxS + (Math.random() - 0.5) * fxJ;
p.delta.x *= fxD;
p.delta.y *= fxD;
p.pos.x += p.delta.x * this.direction;
p.pos.y += p.delta.y * this.direction;
if(this.mouseFX.on){
x = p.pos.x - mouse.x;
y = p.pos.y - mouse.y;
d = Math.sqrt(x * x + y * y);
if(d < mD){
x /= d;
y /= d;
d /= mD;
d = (1-Math.pow(d, mC)) * mP;
p.pos.x += x * d;
p.pos.y += y * d;
}
}
}
return this;
},
findCenter(){ // find the center of particles maybe could do without
var x,y;
y = x = 0;
this.each(p => { x += p.home.x; y += p.home.y });
this.center = Vec(x / this.length, y / this.length);
return this;
},
moveOffscreen(){ // move start pos offscreen
var dist,x,y;
dist = Math.sqrt(this.center.x * this.center.x + this.center.y * this.center.y);
this.each(p => {
var d;
x = p.home.x - this.center.x;
y = p.home.y - this.center.y;
d = Math.max(0.0001,Math.sqrt(x * x + y * y)); // max to make sure no zeros
p.pos.x = p.home.x + (x / d) * dist;
p.pos.y = p.home.y + (y / d) * dist;
});
return this;
},
}
canvas { position : absolute; top : 0px; left : 0px; background : black;}
<canvas id="canvas"></canvas>
Use png saved as PNG-8 and and allow cross-origin
I saw the cool article from Bricks and mortar and thought I'd try it out.
I battled with it for an eternity, thinking that my js was wrong... Turns out that the image has to be saved as a PNG-8 without dither instead of a PNG-24.
Then make sure that you add the crossOrigin="Anonymous" attribute to the image tag:
<img crossOrigin="Anonymous" id="img" src="[link to wherever you host the image]" alt="logo">
I also hid the reference canvas by adding the following styles:
canvas#canvas-reference {
display: none;
}
I also added a debounce and resize function, so it's responsive.
The result:
See Demo with inverted logo

Use Canvas as pad for multiple range inputs

I'm trying to build an html canvas pad that will allow a user to drag and drop a dot on the pad, which will then return two values (one for Y axis, and one for Y axis), which I can use to trigger effects using the web audio API.
I've already sorted out the web Audio API portion of the problem.
The User:
Clicks and drags the dot to anywhere on the X/Y grid
On Drop we will have an X & Y value (perhaps in hidden range inputs), that trigger eventListeners.
The X value eventListener affects the wet/dry of the delay effect
The Y value eventListener affects the delay_time of the delay effect
so far I've been able to create and render the canvas and circle, and add event listeners on the svg element and the window. With the idea being that I can detect when an event occurs inside the canvas and when that click event leaves the canvas.
// Draw SVG pad
function drawDelayPad() {
var canvas = document.getElementById('delayPad');
if (canvas.getContext) {
var ctx = canvas.getContext('2d');
var rectangle = new Path2D();
rectangle.rect(1, 1, 200, 200);
var circle = new Path2D();
circle.moveTo(150, 150);
circle.arc(100, 35, 10, 0 , 2 * Math.PI);
ctx.stroke(rectangle);
ctx.fill(circle);
}
}
// Listener on canvas
var canvas = document.getElementById('delayPad');
canvas.addEventListener("mousedown", function(){
console.log("click inside our canvas")
})
// Listener on document to check if we're outside the canvas
window.addEventListener("mouseup", function(){
console.log("outside our canvas")
});
So I think what I need to determine now is that when a click event does occur inside of the canvas, how far it is from the cirle, and if it does fall within the bounds of the circle, I should redraw it as long as the mousedown event is active.
Any help would be greatly appreciated.
I've found a nice little solution that kind of confirms my suspicions surrounding a hit counter! All credit really goes to rectangleWorld since I was for the most part just able to modify the example they had available.
Here's a codepen
// Draw SVG pad
function canvasApp(canvasID) {
var theCanvas = document.getElementById(canvasID);
var context = theCanvas.getContext("2d");
init();
var numShapes;
var shapes;
var dragIndex;
var dragging;
var mouseX;
var mouseY;
var dragHoldX;
var dragHoldY;
function init() {
numShapes = 1;
shapes = [];
makeShapes();
drawScreen();
theCanvas.addEventListener("mousedown", mouseDownListener, false);
}
function makeShapes() {
var i;
var tempX;
var tempY;
var tempRad;
var tempR;
var tempG;
var tempB;
var tempColor;
var tempShape;
for (i = 0; i < numShapes; i++) {
// My canvas element is 240x240
tempRad = 10;
tempX = 0 + tempRad;
tempY = 240 - tempRad;
tempR = Math.floor(Math.random() * 255);
tempG = Math.floor(Math.random() * 255);
tempB = Math.floor(Math.random() * 255);
tempColor = "rgb(" + tempR + "," + tempG + "," + tempB + ")";
tempShape = {
x: tempX,
y: tempY,
rad: tempRad,
color: tempColor
};
shapes.push(tempShape);
}
}
function mouseDownListener(evt) {
var i;
//We are going to pay attention to the layering order of the objects so that if a mouse down occurs over more than object,
//only the topmost one will be dragged.
var highestIndex = -1;
//getting mouse position correctly, being mindful of resizing that may have occured in the browser:
var bRect = theCanvas.getBoundingClientRect();
mouseX = (evt.clientX - bRect.left) * (theCanvas.width / bRect.width);
mouseY = (evt.clientY - bRect.top) * (theCanvas.height / bRect.height);
//find which shape was clicked
for (i = 0; i < numShapes; i++) {
if (hitTest(shapes[i], mouseX, mouseY)) {
dragging = true;
if (i > highestIndex) {
//We will pay attention to the point on the object where the mouse is "holding" the object:
dragHoldX = mouseX - shapes[i].x;
dragHoldY = mouseY - shapes[i].y;
highestIndex = i;
dragIndex = i;
}
}
}
if (dragging) {
window.addEventListener("mousemove", mouseMoveListener, false);
}
theCanvas.removeEventListener("mousedown", mouseDownListener, false);
window.addEventListener("mouseup", mouseUpListener, false);
//code below prevents the mouse down from having an effect on the main browser window:
if (evt.preventDefault) {
evt.preventDefault();
} //standard
else if (evt.returnValue) {
evt.returnValue = false;
} //older IE
return false;
}
function mouseUpListener(evt) {
theCanvas.addEventListener("mousedown", mouseDownListener, false);
window.removeEventListener("mouseup", mouseUpListener, false);
if (dragging) {
dragging = false;
window.removeEventListener("mousemove", mouseMoveListener, false);
}
}
function mouseMoveListener(evt) {
var posX;
var posY;
var shapeRad = shapes[dragIndex].rad;
var minX = shapeRad;
var maxX = theCanvas.width - shapeRad;
var minY = shapeRad;
var maxY = theCanvas.height - shapeRad;
//getting mouse position correctly
var bRect = theCanvas.getBoundingClientRect();
mouseX = (evt.clientX - bRect.left) * (theCanvas.width / bRect.width);
mouseY = (evt.clientY - bRect.top) * (theCanvas.height / bRect.height);
// Divide by width of canvas and multiply to get percentage out of 100
var DelayTime = ((mouseX / 240) * 100);
// Invert returned value to get percentage out of 100
var DelayFeedback = (100 - (mouseY / 240) * 100);
// Set delay time as a portion of 2seconds
delayEffect.delayTime.value = DelayTime / 100 * 2.0;
// set delay feedback gain as value of random number
delayFeedback.gain.value = (DelayFeedback / 100 * 1.0);
//clamp x and y positions to prevent object from dragging outside of canvas
posX = mouseX - dragHoldX;
posX = (posX < minX) ? minX : ((posX > maxX) ? maxX : posX);
posY = mouseY - dragHoldY;
posY = (posY < minY) ? minY : ((posY > maxY) ? maxY : posY);
shapes[dragIndex].x = posX;
shapes[dragIndex].y = posY;
drawScreen();
}
function hitTest(shape, mx, my) {
var dx;
var dy;
dx = mx - shape.x;
dy = my - shape.y;
//a "hit" will be registered if the distance away from the center is less than the radius of the circular object
return (dx * dx + dy * dy < shape.rad * shape.rad);
}
function drawShapes() {
var i;
for (i = 0; i < numShapes; i++) {
context.fillStyle = shapes[i].color;
context.beginPath();
context.arc(shapes[i].x, shapes[i].y, shapes[i].rad, 0, 2 * Math.PI, false);
context.closePath();
context.fill();
}
}
function drawScreen() {
context.fillStyle = "#000000";
context.fillRect(0, 0, theCanvas.width, theCanvas.height);
drawShapes();
}
}
window.addEventListener("load", windowLoadHandler, false);
function windowLoadHandler() {
canvasApp('delayPad');
}
There are still a few shortcomings, for instance the mouseMoveListener, although constricting the movement of the circle, will continue to increase your x & y values. Meaning you'll either have to use your existing listeners to check when the drag event has exited the circle, or much more simply, you could set an upper limit to your X and Y values.
You'll have to create an object which will store your x and y values.
In below example I called it pad.
This object will serve both your canvas visualization, and your audio processing.
These are both outputs (respectively visual and audio), while the input will be user gesture (e.g mousemove).
The inputs update the pad object, while outputs read it.
[Note]: This example will only work in newest Chrome and Firefox since it uses MediaElement.captureStream() which is not yet widely implemented.
const viz_out = canvas.getContext('2d');
let aud_out, mainVolume;
// our pad object holding the coordinates
const pad = {
x: 0,
y: 0,
down: false,
rad: 10
};
let canvRect = canvas.getBoundingClientRect();
function mousemove(event) {
if (!aud_out || !pad.down) {
return;
}
pad.x = event.clientX - canvRect.left;
pad.y = canvRect.height - (event.clientY - canvRect.top); // inverts y axis
// all actions are splitted
updateViz();
updateAud();
updateLog();
}
viz_out.setTransform(1, 0, 0, -1, 0, 300) // invert y axis on the canvas too
// simply draws a circle where at our pad's coords
function updateViz() {
viz_out.clearRect(0, 0, canvas.width, canvas.height);
viz_out.beginPath();
viz_out.arc(pad.x, pad.y, pad.rad, 0, Math.PI * 2);
viz_out.fill();
}
// You'll do it as you wish, here it just modifies a biquadFilter
function updateAud() {
const default_freq = 350;
const max_freq = 6000;
const y_ratio = pad.y / 300;
aud_out.frequency.value = (default_freq + (max_freq * y_ratio)) - default_freq;
aud_out.Q.value = (pad.x / 300) * 10;
mainVolume.value = 1 + ((pad.y + pad.x) / 75);
}
function updateLog() {
log.textContent = `x:${~~pad.x} y:${~~pad.y}`;
}
canvas.addEventListener('mousedown', e => pad.down = true);
canvas.addEventListener('mouseup', e => pad.down = false);
canvas.addEventListener('mousemove', mousemove);
btn.onclick = e => {
btn.textContent = 'stop';
startLoadingAudio();
btn.onclick = e => {
mainVolume.value = 0;
}
}
window.onscroll = window.onresize = e => canvRect = canvas.getBoundingClientRect();
function startLoadingAudio() {
const audio = new Audio();
audio.loop = true;
audio.muted = true;
audio.onloadedmetadata = e => {
audio.play();
const stream = audio.captureStream ? audio.captureStream() : audio.mozCaptureStream();
initAudioProcessor(stream);
updateLog();
window.onscroll();
updateViz();
}
// FF will "taint" the stream, even if the media is served with correct CORS...
fetch("https://dl.dropboxusercontent.com/s/8c9m92u1euqnkaz/GershwinWhiteman-RhapsodyInBluePart1.mp3").then(resp => resp.blob()).then(b => audio.src = URL.createObjectURL(b));
function initAudioProcessor(stream) {
var a_ctx = new AudioContext();
var gainNode = a_ctx.createGain();
var biquadFilter = a_ctx.createBiquadFilter();
var source = a_ctx.createMediaStreamSource(stream);
source.connect(biquadFilter);
biquadFilter.connect(gainNode);
gainNode.connect(a_ctx.destination);
aud_out = biquadFilter;
mainVolume = gainNode.gain;
biquadFilter.type = "bandpass";
}
}
canvas {
border: 1px solid;
}
<button id="btn">
start
</button>
<pre id="log"></pre>
<canvas id="canvas" width="300" height="300"></canvas>

How to code an nth order Bezier curve

Trying to code an nth order bezier in javascript on canvas for a project. I want to be able to have the user press a button, in this case 'b', to select each end point and the control points. So far I am able to get the mouse coordinates on keypress and make quadratic and bezier curves using the built in functions. How would I go about making code for nth order?
Here's a Javascript implementation of nth order Bezier curves:
// setup canvas
var canvas = document.getElementById('canvas');
var ctx = canvas.getContext('2d');
canvas.height = window.innerHeight;
canvas.width = window.innerWidth;
ctx.fillText("INSTRUCTIONS: Press the 'b' key to add points to your curve. Press the 'c' key to clear all points and start over.", 20, 20);
// initialize points list
var plist = [];
// track mouse movements
var mouseX;
var mouseY;
document.addEventListener("mousemove", function(e) {
mouseX = e.clientX;
mouseY = e.clientY;
});
// from: http://rosettacode.org/wiki/Evaluate_binomial_coefficients#JavaScript
function binom(n, k) {
var coeff = 1;
for (var i = n - k + 1; i <= n; i++) coeff *= i;
for (var i = 1; i <= k; i++) coeff /= i;
return coeff;
}
// based on: https://stackoverflow.com/questions/16227300
function bezier(t, plist) {
var order = plist.length - 1;
var y = 0;
var x = 0;
for (i = 0; i <= order; i++) {
x = x + (binom(order, i) * Math.pow((1 - t), (order - i)) * Math.pow(t, i) * (plist[i].x));
y = y + (binom(order, i) * Math.pow((1 - t), (order - i)) * Math.pow(t, i) * (plist[i].y));
}
return {
x: x,
y: y
};
}
// draw the Bezier curve
function draw(plist) {
ctx.clearRect(0, 0, canvas.width, canvas.height);
var accuracy = 0.01; //this'll give the 100 bezier segments
ctx.beginPath();
ctx.moveTo(plist[0].x, plist[0].y);
for (p in plist) {
ctx.fillText(p, plist[p].x + 5, plist[p].y - 5);
ctx.fillRect(plist[p].x - 5, plist[p].y - 5, 10, 10);
}
for (var i = 0; i < 1; i += accuracy) {
var p = bezier(i, plist);
ctx.lineTo(p.x, p.y);
}
ctx.stroke();
ctx.closePath();
}
// listen for keypress
document.addEventListener("keydown", function(e) {
switch (e.keyCode) {
case 66:
// b key
plist.push({
x: mouseX,
y: mouseY
});
break;
case 67:
// c key
plist = [];
break;
}
draw(plist);
});
html,
body {
height: 100%;
margin: 0 auto;
}
<canvas id="canvas"></canvas>
This is based on this implementation of cubic Bezier curves. In your application, it sounds like you'll want to populate the points array with user-defined points.
Here is a code example for any number of points you want to add to make a bezier curve. Here points you will pass is an array of objects containing x and y values of points. [ { x: 1,y: 2 } , { x: 3,y: 4} ... ]
function factorial(n) {
if(n<0)
return(-1); /*Wrong value*/
if(n==0)
return(1); /*Terminating condition*/
else
{
return(n*factorial(n-1));
}
}
function nCr(n,r) {
return( factorial(n) / ( factorial(r) * factorial(n-r) ) );
}
function BezierCurve(points) {
let n=points.length;
let curvepoints=[];
for(let u=0; u <= 1 ; u += 0.0001 ){
let p={x:0,y:0};
for(let i=0 ; i<n ; i++){
let B=nCr(n-1,i)*Math.pow((1-u),(n-1)-i)*Math.pow(u,i);
let px=points[i].x*B;
let py=points[i].y*B;
p.x+=px;
p.y+=py;
}
curvepoints.push(p);
}
return curvepoints;
}

Where should I place this condition?

For the last step of this project, I want the growing circle to stop when it collides with another circle. The isOnCircle function already checks for this successfully when creating a new circle. However, when adding the condition !isOnCircle to my grow() function (line 61) it prevents any new circles from being added.
function grow() {
var a = circles[circles.length - 1];
if (!isOnCircle(a)){
a.radius += 1;
}}
Perhaps the circle is being created first, then in the check for collision, it's colliding with itself. Where else could I put the !isOnCircle check so that it gets checked at every radius increase and stops the grow function then?
check this
//set up canvas
var canvas = document.getElementById("canvas");
var ctx = canvas.getContext("2d");
var circles = [];
//create circle
function create(location) {
circles.push({
x: location.x,
y: location.y,
radius: 10,
color: '#' + Math.floor(Math.random() * 16777215).toString(16)
});
}
//figure out mouse position
var rect = document.getElementById("canvas").getBoundingClientRect();
// Get canvas offset on page
var offset = {
x: rect.left,
y: rect.top
};
function isOnCanvas(a) {
if ((a.x >= 0 && a.x <= rect.width) && (a.y >= 0 && a.y <= rect.height)) {
return true;
}
return false;
}
function isOnCircle(a) {
var i = 0,
l = circles.length,
x, y, d, c;
for (; i < l; ++i) {
c = circles[i];
x = a.x - c.x;
y = a.y - c.y;
d = (a.radius || 10) + c.radius;
if (x * x + y * y <= d * d) {
return true;
}
}
return false;
}
// draw all circles
function draw() {
ctx.clearRect(0, 0, canvas.width, canvas.height);
for (var i = 0; i < circles.length; i++) {
var p = circles[i];
ctx.beginPath();
ctx.arc(p.x, p.y, p.radius, 0, 2 * Math.PI);
ctx.fillStyle = p.color;
ctx.fill();
}
}
//make last drawn circle 1px bigger
function grow() {
var a = circles[circles.length - 1];
a.radius += 1;
}
//find percentage of canvas filled in
var totalSpace = canvas.width * canvas.height;
var totalFilled = function () {
total = 0;
for (var i = 0; i < circles.length; i++) {
var p = circles[i];
total += Math.PI * Math.pow(p.radius, 2);
}
return total;
console.log(total);
}
function findPercentage() {
return (totalFilled() / totalSpace) * 100;
}
function updateInfo() {
percentage = findPercentage();
document.getElementById("percentage").innerHTML = "You've filled in " + percentage.toFixed(1) + "%";
}
//do all the stuff
var animate = function () {
grow();
draw();
updateInfo();
}
//put this outside function so we can stop it later
var growLoop;
window.onmousedown = function (e) {
// get event location on page offset by canvas location
var location = {
x: e.pageX - offset.x,
y: e.pageY - offset.y
};
if (isOnCanvas(location) && !isOnCircle(location)) {
create(location);
draw();
updateInfo();
growLoop = setInterval(animate, 100);
}
};
window.onmouseup = function () {
clearInterval(growLoop);
}
window.onmouseout = function () {
clearInterval(growLoop);
}
it's colliding with itself.
Probably. You definitely should avoid that in the collision detection:
function isOnCircle(a) {
var l = circles.length,
x, y, d, c;
for (var i = 0; i < l; ++i) {
c = circles[i];
if (a == c) // add these
continue; // two lines!
x = a.x - c.x;
y = a.y - c.y;
d = (a.radius || 10) + c.radius;
if (x * x + y * y <= d * d) {
return true;
}
}
return false;
}
It is colliding with itself. Since you know the current circle will always be the last one in circles you can modify isOnCircle like this:
l = circles.length - 1,
so that it won't check against the current circle.
http://jsfiddle.net/SeAGU/91/

Detect mouse click location within canvas

I'm having a real issue trying to define a function for where I click on empty space. So far I have managed to define where I click on an object - of which there are 10 - but now I need a separate function for when I am not clicking on any of the objects. The general idea can be found at http://deciballs.co.uk/experience.html. The objects are the rings. My code is below... Any ideas?
var shapeObj = function (context, canvas, settingsBox, radius) {
this.ctx = context;
this.canvas = canvas;
this.sBox = settingsBox;
this.frequencies = new Array(220, 440, 1024, 2048);
this.cols = new Array(255, 225, 200, 175, 150);
this.strokes = new Array(1, 1.5, 2);
this.waves = new Array('sine', 'sawtooth', 'triangle', 'square');
this.properties = {
dur: Math.random()*0.5,
freq: this.frequencies[Math.floor(Math.random() * this.frequencies.length)],
radius: radius,
stroke: this.strokes[Math.floor(Math.random() * this.strokes.length)],
speed: Math.random()*6-3,
vol: Math.random()*10,
col1: this.cols[Math.floor(Math.random() * this.cols.length)],
col2: this.cols[Math.floor(Math.random() * this.cols.length)],
col3: this.cols[Math.floor(Math.random() * this.cols.length)],
alpha: 0,
wave: this.waves[Math.floor(Math.random() * this.waves.length)],
delay: 0
}
this.x = Math.random()*this.ctx.canvas.width;
this.y = Math.random()*this.ctx.canvas.height;
this.vx = 0.5;
this.vy = 1;
this.draw = function () {
this.ctx.beginPath();
this.ctx.arc(this.x, this.y, this.properties.radius, 0, Math.PI*2, false);
this.ctx.closePath();
this.ctx.stroke();
this.ctx.fill();
}
this.clickTest = function (e) {
var canvasOffset = this.canvas.offset();
var canvasX = Math.floor(e.pageX-canvasOffset.left);
var canvasY = Math.floor(e.pageY-canvasOffset.top);
var dX = this.x-canvasX;
var dY = this.y-canvasY;
var distance = Math.sqrt((dX*dX)+(dY*dY));
if (distance < this.properties.radius) {
this.manageClick();
} else {
this.properties.alpha = 0;
}
};
this.manageClick = function () {
this.sBox.populate(this.properties, this);
var divs = document.getElementsByTagName('section');
for(var i = 0, e = divs[0], n = divs.length; i < n; e = divs[++i]){
e.className='class2';
}
this.properties.alpha = 0.5;
}
}
Getting perfect mouse clicks is slightly tricky, I'll share the most bulletproof mouse code that I have created thus far. It works on all browsers will all manner of padding, margin, border, and add-ons (like the stumbleupon top bar).
// Creates an object with x and y defined,
// set to the mouse position relative to the state's canvas
// If you wanna be super-correct this can be tricky,
// we have to worry about padding and borders
// takes an event and a reference to the canvas
function getMouse(e, canvas) {
var element = canvas, offsetX = 0, offsetY = 0, mx, my;
// Compute the total offset. It's possible to cache this if you want
if (element.offsetParent !== undefined) {
do {
offsetX += element.offsetLeft;
offsetY += element.offsetTop;
} while ((element = element.offsetParent));
}
// Add padding and border style widths to offset
// Also add the <html> offsets in case there's a position:fixed bar (like the stumbleupon bar)
// This part is not strictly necessary, it depends on your styling
offsetX += stylePaddingLeft + styleBorderLeft + htmlLeft;
offsetY += stylePaddingTop + styleBorderTop + htmlTop;
mx = e.pageX - offsetX;
my = e.pageY - offsetY;
// We return a simple javascript object with x and y defined
return {x: mx, y: my};
}
You'll notice that I use some (optional) variables that are undefined in the function. They are:
stylePaddingLeft = parseInt(document.defaultView.getComputedStyle(canvas, null)['paddingLeft'], 10) || 0;
stylePaddingTop = parseInt(document.defaultView.getComputedStyle(canvas, null)['paddingTop'], 10) || 0;
styleBorderLeft = parseInt(document.defaultView.getComputedStyle(canvas, null)['borderLeftWidth'], 10) || 0;
styleBorderTop = parseInt(document.defaultView.getComputedStyle(canvas, null)['borderTopWidth'], 10) || 0;
// Some pages have fixed-position bars (like the stumbleupon bar) at the top or left of the page
// They will mess up mouse coordinates and this fixes that
var html = document.body.parentNode;
htmlTop = html.offsetTop;
htmlLeft = html.offsetLeft;
I'd recommend only computing those once, which is why they are not in the getMouse function.
You should really have a single function hat handles mouse clicks, calls getMouse once, and then goes though a list of objects, checking against each one with the x and y. Pseudocode:
function onMouseDown(e) {
var mouse = getMouse(e, canvas)
var l = myObjects.length;
var found = false;
// Maybe "deselect" them all right here
for (var i = 0; i < l; i++) {
if (distance sqrt to myObjects[i]) {
found = true;
myObjects[i].ManageClickOrWhateverYouWantHere()
}
break;
}
// And now we can know if we clicked on empty space or not!
if (!found) {
// No objects found at the click, so nothing has been clicked on
// do some relevant things here because of that
// I presume from your question this may be part of what you want
}
}

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