Hi I want to make a blur effect particle like this:
Can I use shadowBlur and shadowOffsetX/shadowOffsetY to do this? The actual shine will glow and fade a little bit repeatedly, so if I have to write some kind of animation how can I achieve this?
I have tried this code (jsfiddle example) but it doesn't look like the effect. So I wonder how to blur and glow the particle at the same time?
const canvas = document.getElementById('canvas');
const ctx = canvas.getContext('2d');
canvas.width = window.innerWidth;
canvas.height = window.innerHeight;
const ra = window.requestAnimationFrame
|| window.webkitRequestAnimationFrame
|| window.mozRequestAnimationFrame
|| window.oRequestAnimationFrame
|| window.msRequestAnimationFrame
|| function(callback) {
window.setTimeout(callback, 1000 / 60);
};
class Particle {
constructor(options) {
this.ctx = options.context;
this.x = options.x;
this.y = options.y;
this.radius = options.radius;
this.lightSize = this.radius;
this.color = options.color;
this.lightDirection = true;
}
glow() {
const lightSpeed = 0.5;
this.lightSize += this.lightDirection ? lightSpeed : -lightSpeed;
if (this.lightSize > this.radius || this.lightSize < this.radius) {
this.lightDirection = !this.lightDirection;
}
}
render() {
this.ctx.clearRect(0, 0, canvas.width, canvas.height);
this.glow();
this.ctx.globalAlpha = 0.5;
this.ctx.fillStyle = this.color;
this.ctx.beginPath();
this.ctx.arc(this.x, this.y, this.lightSize,
0, Math.PI * 2
);
this.ctx.fill();
this.ctx.globalAlpha = 0.62;
this.ctx.beginPath();
this.ctx.arc(this.x, this.y, this.radius * 0.7, 0, Math.PI * 2);
this.ctx.shadowColor = this.color;
this.ctx.shadowBlur = 6;
this.ctx.shadowOffsetX = 0;
this.ctx.shadowOffsetY = 0;
this.ctx.fill();
}
}
var particle = new Particle({
context: ctx,
x: 60,
y: 80,
radius: 12,
color: '#4d88ff'
});
function run() {
particle.render();
ra(run);
}
run();
<canvas id='canvas'></canvas>
There are several ways to do this. For a particle system my option is to pre render the blur using a blur filter. A common filter is the convolution filter. It uses a small array to determine the amount neighboring pixels contribute to each pixel of the image. You are best to look up convolution functions to understand it.
Wiki Convolution and Wiki Gaussian blur for more info.
I am not much of a fan of the standard Gaussian blur or the convolution filter used so in the demo snippet below you can find my version that I think creates a much better blur. The convolution blur filter is procedurally created and is in the imageTools object.
To use create a filter pass an object with properties size the blur amount in pixels and power is the strength. Lower powers is less spread on the blur.
// image must be loaded or created
var blurFilter = imageTools.createBlurConvolutionArray({size:17,power:1}); // size must be greater than 2 and must be odd eg 3,5,7,9...
// apply the convolution filter on the image. The returned image may be a new
//image if the input image does not have a ctx property pointing to a 2d canvas context
image = imageTools.applyConvolutionFilter(image,blurFilter);
In the demo I create a image, draw a circle on it, copy it and pad it so that there is room for the blur. Then create a blur filter and apply it to the image.
When I render the particles I first draw all the unblurred images, then draw the blurred copies with the ctx.globalCompositeOperation = "screen"; so that they have a shine. To vary the amount of shine I use the ctx.globalAlpha to vary the intensity of the rendered blurred image. To improve the FX I have drawn the blur image twice, once with oscillating scale and next at fixed scale and alpha.
The demo is simple, image tools can be found at the top. Then there is some stuff to setup the canvas and handle resize event. Then there is the code that creates the images, and apply the filters. Then starts the render adds some particles and renders everything.
Look in the function drawParticles for how I draw everything.
imageTools has all the image functions you will need. The imageTools.applyConvolutionFilter will apply any filter (sharpen, outline, and many more) you just need to create the appropriate filter. The apply uses the photon count colour model so gives a very high quality result especially for blurs type effects. (though for sharpen you may want to get in and change the squaring of the RGB values, I personally like it other do not)
The blur filter is not fast so if you apply it to larger images It would be best that you break it up in so you do not block the page execution.
A cheap way to get a blur is to copy the image to blur to a smaller version of itself, eg 1/4 then render it scaled back to normal size, the canvas will apply bilinear filtering on the image give a blur effect. Not the best quality but for most situations it is indistinguishable from the more sophisticated blur that I have presented.
UPDATE
Change the code so that the particles have a bit of a 3dFX to show that the blur can work up to larger scales. The blue particles are 32 by 32 image and the blur is 9 pixels with the blur image being 50by 50 pixels.
var imageTools = (function () {
var tools = {
canvas : function (width, height) { // create a blank image (canvas)
var c = document.createElement("canvas");
c.width = width;
c.height = height;
return c;
},
createImage : function (width, height) {
var image = this.canvas(width, height);
image.ctx = image.getContext("2d");
return image;
},
image2Canvas : function (img) {
var image = this.canvas(img.width, img.height);
image.ctx = image.getContext("2d");
image.drawImage(img, 0, 0);
return image;
},
padImage : function(img,amount){
var image = this.canvas(img.width + amount * 2, img.height + amount * 2);
image.ctx = image.getContext("2d");
image.ctx.drawImage(img, amount, amount);
return image;
},
getImageData : function (image) {
return (image.ctx || (this.image2Canvas(image).ctx)).getImageData(0, 0, image.width, image.height);
},
putImageData : function (image, imgData){
(image.ctx || (this.image2Canvas(image).ctx)).putImageData(imgData,0, 0);
return image;
},
createBlurConvolutionArray : function(options){
var i, j, d; // misc vars
var filterArray = []; // the array to create
var size = options.size === undefined ? 3: options.size; // array size
var center = Math.floor(size / 2); // center of array
// the power ? needs descriptive UI options
var power = options.power === undefined ? 1: options.power;
// dist to corner
var maxDist = Math.sqrt(center * center + center * center);
var dist = 0; // distance sum
var sum = 0; // weight sum
var centerWeight; // center calculated weight
var totalDistance; // calculated total distance from center
// first pass get the total distance
for(i = 0; i < size; i++){
for(j = 0; j < size; j++){
d = (maxDist-Math.sqrt((center-i)*(center-i)+(center-j)*(center-j)));
d = Math.pow(d,power)
dist += d;
}
}
totalDistance = dist; // total distance to all points;
// second pass get the total weight of all but center
for(i = 0; i < size; i++){
for(j = 0; j < size; j++){
d = (maxDist-Math.sqrt((center-i)*(center-i)+(center-j)*(center-j)));
d = Math.pow(d,power)
d = d/totalDistance;
sum += d;
}
}
var scale = 1/sum;
sum = 0; // used to check
for(i = 0; i < size; i++){
for(j = 0; j < size; j++){
d = (maxDist-Math.sqrt((center-i)*(center-i)+(center-j)*(center-j)));
d = Math.pow(d,power)
d = d/totalDistance;
filterArray.push(d*scale);
}
}
return filterArray;
},
applyConvolutionFilter : function(image,filter){
imageData = this.getImageData(image);
imageDataResult = this.getImageData(image);
var w = imageData.width;
var h = imageData.height;
var data = imageData.data;
var data1 = imageDataResult.data;
var side = Math.round(Math.sqrt(filter.length));
var halfSide = Math.floor(side/2);
var r,g,b,a,c;
for(var y = 0; y < h; y++){
for(var x = 0; x < w; x++){
var ind = y*4*w+x*4;
r = 0;
g = 0;
b = 0;
a = 0;
for (var cy=0; cy<side; cy++) {
for (var cx=0; cx<side; cx++) {
var scy = y + cy - halfSide;
var scx = x + cx - halfSide;
if (scy >= 0 && scy < h && scx >= 0 && scx < w) {
var srcOff = (scy*w+scx)*4;
var wt = filter[cy*side+cx];
r += data[srcOff+0] * data[srcOff+0] * wt;
g += data[srcOff+1] * data[srcOff+1] * wt;
b += data[srcOff+2] * data[srcOff+2] * wt;
a += data[srcOff+3] * data[srcOff+3] * wt;
}
}
}
data1[ind+0] = Math.sqrt(Math.max(0,r));
data1[ind+1] = Math.sqrt(Math.max(0,g));
data1[ind+2] = Math.sqrt(Math.max(0,b));
data1[ind+3] = Math.sqrt(Math.max(0,a));
}
}
return this.putImageData(image,imageDataResult);
}
};
return tools;
})();
/** SimpleFullCanvasMouse.js begin **/
const CANVAS_ELEMENT_ID = "canv";
const U = undefined;
var w, h, cw, ch; // short cut vars
var canvas, ctx;
var globalTime = 0;
var createCanvas, resizeCanvas, setGlobals;
var L = typeof log === "function" ? log : function(d){ console.log(d); }
createCanvas = function () {
var c,cs;
cs = (c = document.createElement("canvas")).style;
c.id = CANVAS_ELEMENT_ID;
cs.position = "absolute";
cs.top = cs.left = "0px";
cs.zIndex = 1000;
document.body.appendChild(c);
return c;
}
resizeCanvas = function () {
if (canvas === U) { canvas = createCanvas(); }
canvas.width = window.innerWidth;
canvas.height = window.innerHeight;
ctx = canvas.getContext("2d");
if (typeof setGlobals === "function") { setGlobals(); }
}
setGlobals = function(){
cw = (w = canvas.width) / 2; ch = (h = canvas.height) / 2;
if(particles && particles.length > 0){
particles.length = 0;
}
}
resizeCanvas(); // create and size canvas
window.addEventListener("resize",resizeCanvas); // add resize event
const IMAGE_SIZE = 32;
const IMAGE_SIZE_HALF = 16;
const GRAV = 2001;
const NUM_PARTICLES = 90;
var background = imageTools.createImage(8,8);
var grad = ctx.createLinearGradient(0,0,0,8);
grad.addColorStop(0,"#000");
grad.addColorStop(1,"#048");
background.ctx.fillStyle = grad;
background.ctx.fillRect(0,0,8,8);
var circle = imageTools.createImage(IMAGE_SIZE,IMAGE_SIZE);
circle.ctx.fillStyle = "#5BF";
circle.ctx.arc(IMAGE_SIZE_HALF, IMAGE_SIZE_HALF, IMAGE_SIZE_HALF -2,0, Math.PI * 2);
circle.ctx.fill();
var blurFilter = imageTools.createBlurConvolutionArray({size:9,power:1}); // size must be greater than 2 and must be odd eg 3,5,7,9...
var blurCircle = imageTools.padImage(circle,9);
blurCircle = imageTools.applyConvolutionFilter(blurCircle,blurFilter)
var sun = imageTools.createImage(64,64);
grad = ctx.createRadialGradient(32,32,0,32,32,32);
grad.addColorStop(0,"#FF0");
grad.addColorStop(1,"#A40");
sun.ctx.fillStyle = grad;
sun.ctx.arc(32,32,32 -2,0, Math.PI * 2);
sun.ctx.fill();
var sunBlur = imageTools.padImage(sun,17);
blurFilter = imageTools.createBlurConvolutionArray({size:17,power:1}); // size must be greater than 2 and must be odd eg 3,5,7,9...
sunBlur = imageTools.applyConvolutionFilter(sunBlur,blurFilter);
var particles = [];
var createParticle = function(x,y,dx,dy){
var dir = Math.atan2(y-ch,x-cw);
var dist = Math.sqrt(Math.pow(y-ch,2)+Math.pow(x-cw,2));
var v = Math.sqrt(GRAV / dist); // get apporox orbital speed
return {
x : x,
y : y,
dx : dx + Math.cos(dir + Math.PI/2) * v, // set orbit speed at tangent
dy : dy + Math.sin(dir + Math.PI/2) * v,
s : (Math.random() + Math.random() + Math.random())/4 + 0.5, // scale
v : (Math.random() + Math.random() + Math.random()) / 3 + 2, // glow vary rate
};
}
var depthSort = function(a,b){
return b.y - a.y;
}
var updateParticles = function(){
var i,p,f,dist,dir;
for(i = 0; i < particles.length; i ++){
p = particles[i];
dist = Math.sqrt(Math.pow(cw-p.x,2)+Math.pow(ch-p.y,2));
dir = Math.atan2(ch-p.y,cw-p.x);
f = GRAV * 1 / (dist * dist);
p.dx += Math.cos(dir) * f;
p.dy += Math.sin(dir) * f;
p.x += p.dx;
p.y += p.dy;
p.rx = ((p.x - cw ) / (p.y + h)) * h + cw;
p.ry = ((p.y - ch ) / (p.y + h)) * h * -0.051+ ch;
//p.ry = ((h-p.y) - ch) * 0.1 + ch;
p.rs = (p.s / (p.y + h)) * h
}
particles.sort(depthSort)
}
var drawParticles = function(){
var i,j,p,f,dist,dir;
// draw behind the sun
for(i = 0; i < particles.length; i ++){
p = particles[i];
if(p.y - ch < 0){
break;
}
ctx.setTransform(p.rs,0,0,p.rs,p.rx,p.ry);
ctx.drawImage(circle,-IMAGE_SIZE_HALF,-IMAGE_SIZE_HALF);
}
// draw glow for behind the sun
ctx.globalCompositeOperation = "screen";
var iw = -blurCircle.width/2;
for(j = 0; j < i; j ++){
p = particles[j];
ctx.globalAlpha = ((Math.sin(globalTime / (50 * p.v)) + 1) / 2) * 0.6 + 0.4;
var scale = (1-(Math.sin(globalTime / (50 * p.v)) + 1) / 2) * 0.6 + 0.6;
ctx.setTransform(p.rs * 1.5 * scale,0,0,p.rs * 1.5* scale,p.rx,p.ry);
ctx.drawImage(blurCircle,iw,iw);
// second pass to intensify the glow
ctx.globalAlpha = 0.7;
ctx.setTransform(p.rs * 1.1,0,0,p.rs * 1.1,p.rx,p.ry);
ctx.drawImage(blurCircle,iw,iw);
}
// draw the sun
ctx.globalCompositeOperation = "source-over";
ctx.globalAlpha = 1;
ctx.setTransform(1,0,0,1,cw,ch);
ctx.drawImage(sun,-sun.width/2,-sun.height/2);
ctx.globalAlpha = 1;
ctx.globalCompositeOperation = "screen";
ctx.setTransform(1,0,0,1,cw,ch);
ctx.drawImage(sunBlur,-sunBlur.width/2,-sunBlur.height/2);
var scale = Math.sin(globalTime / 100) *0.5 + 1;
ctx.globalAlpha = (Math.cos(globalTime / 100) + 1) * 0.2 + 0.4;;
ctx.setTransform(1 + scale,0,0,1 + scale,cw,ch);
ctx.drawImage(sunBlur,-sunBlur.width/2,-sunBlur.height/2);
ctx.globalAlpha = 1;
ctx.globalCompositeOperation = "source-over";
// draw in front the sun
for(j = i; j < particles.length; j ++){
p = particles[j];
if(p.y > -h){ // don't draw past the near view plane
ctx.setTransform(p.rs,0,0,p.rs,p.rx,p.ry);
ctx.drawImage(circle,-IMAGE_SIZE_HALF,-IMAGE_SIZE_HALF);
}
}
ctx.globalCompositeOperation = "screen";
var iw = -blurCircle.width/2;
for(j = i; j < particles.length; j ++){
p = particles[j];
if(p.y > -h){ // don't draw past the near view plane
ctx.globalAlpha = ((Math.sin(globalTime / (50 * p.v)) + 1) / 2) * 0.6 + 0.4;
var scale = (1-(Math.sin(globalTime / (50 * p.v)) + 1) / 2) * 0.6 + 0.6;
ctx.setTransform(p.rs * 1.5 * scale,0,0,p.rs * 1.5* scale,p.rx,p.ry);
ctx.drawImage(blurCircle,iw,iw);
// second pass to intensify the glow
ctx.globalAlpha = 0.7;
ctx.setTransform(p.rs * 1.1,0,0,p.rs * 1.1,p.rx,p.ry);
ctx.drawImage(blurCircle,iw,iw);
}
}
ctx.globalCompositeOperation = "source-over";
}
var addParticles = function(count){
var ww = (h-10)* 2;
var cx = cw - ww/2;
var cy = ch - ww/2;
for(var i = 0; i < count; i ++){
particles.push(createParticle(cx + Math.random() * ww,cy + Math.random() * ww, Math.random() - 0.5, Math.random() - 0.5));
}
}
function display(){ // put code in here
if(particles.length === 0){
addParticles(NUM_PARTICLES);
}
ctx.setTransform(1,0,0,1,0,0); // reset transform
ctx.globalAlpha = 1; // reset alpha
ctx.drawImage(background,0,0,w,h)
updateParticles();
drawParticles();
ctx.globalAlpha = 1;
ctx.globalCompositeOperation = "source-over";
}
function update(timer){ // Main update loop
globalTime = timer;
display(); // call demo code
requestAnimationFrame(update);
}
requestAnimationFrame(update);
/** SimpleFullCanvasMouse.js end **/
Related
I need to build canvas animation like design requires. I spend almost 3 days but I'm not able to do anything like in design. Here a REQUESTED design!. And here - what I've got for now: current implementation which definitely not what requested from design .I need only animation of planet from particles at background (also whole process of animation changes in time, it starts from few particles but then amount growing and movings directions of particles changes)
here my current code:
export class CanvasComponent implements OnInit {
sphereRad = 280;
radius_sp = 1;
distance = 600;
particle_size = 0.7;
constructor() { }
ngOnInit() {
this.canvasApp();
}
canvasApp () {
const canvas = document.querySelector('canvas');
const context = canvas.getContext('2d');
canvas.width = window.innerWidth;
canvas.height = window.innerHeight;
let displayWidth;
let displayHeight;
let wait;
let count;
let numToAddEachFrame;
let particleList;
let recycleBin;
let particleAlpha;
let r, g, b;
let fLen;
let m;
let projCenterX;
let projCenterY;
let zMax;
let turnAngle;
let turnSpeed;
let sphereCenterX, sphereCenterY, sphereCenterZ;
let particleRad;
let zeroAlphaDepth;
let randAccelX, randAccelY, randAccelZ;
let gravity;
let rgbString;
// we are defining a lot of letiables used in the screen update functions globally so that they don't have to be redefined every frame.
let p;
let outsideTest;
let nextParticle;
let sinAngle;
let cosAngle;
let rotX, rotZ;
let depthAlphaFactor;
let i;
let theta, phi;
let x0, y0, z0;
// INITIALLI
const init = () => {
wait = 1;
count = wait - 1;
numToAddEachFrame = 30;
// particle color
r = 255;
g = 255;
b = 255;
rgbString = 'rgba(' + r + ',' + g + ',' + b + ','; // partial string for color which will be completed by appending alpha value.
particleAlpha = 1; // maximum alpha
displayWidth = canvas.width;
displayHeight = canvas.height;
fLen = this.distance; // represents the distance from the viewer to z=0 depth.
// projection center coordinates sets location of origin
projCenterX = displayWidth / 2;
projCenterY = displayHeight / 2;
// we will not draw coordinates if they have too large of a z-coordinate (which means they are very close to the observer).
zMax = fLen - 2;
particleList = {};
recycleBin = {};
// random acceleration factors - causes some random motion
randAccelX = 0.1;
randAccelY = 0.1;
randAccelZ = 0.1;
gravity = -0; // try changing to a positive number (not too large, for example 0.3), or negative for floating upwards.
particleRad = this.particle_size;
sphereCenterX = 0;
sphereCenterY = 0;
sphereCenterZ = -3 - this.sphereRad;
// alpha values will lessen as particles move further back, causing depth-based darkening:
zeroAlphaDepth = 0;
turnSpeed = 2 * Math.PI / 1200; // the sphere will rotate at this speed (one complete rotation every 1600 frames).
turnAngle = 0; // initial angle
// timer = setInterval(onTimer, 10 / 24);
onTimer();
}
const onTimer = () => {
// if enough time has elapsed, we will add new particles.
count++;
if (count >= wait) {
count = 0;
for (i = 0; i < numToAddEachFrame; i++) {
theta = Math.random() * 2 * Math.PI;
phi = Math.acos(Math.random() * 2 - 1);
x0 = this.sphereRad * Math.sin(phi) * Math.cos(theta);
y0 = this.sphereRad * Math.sin(phi) * Math.sin(theta);
z0 = this.sphereRad * Math.cos(phi);
// We use the addParticle function to add a new particle. The parameters set the position and velocity components.
// Note that the velocity parameters will cause the particle to initially fly outwards away from the sphere center (after
// it becomes unstuck).
const p = addParticle(x0, sphereCenterY + y0, sphereCenterZ + z0, 0.002 * x0, 0.002 * y0, 0.002 * z0);
// we set some 'envelope' parameters which will control the evolving alpha of the particles.
p.attack = 50;
p.hold = 50;
p.decay = 100;
p.initValue = 0;
p.holdValue = particleAlpha;
p.lastValue = 0;
// the particle will be stuck in one place until this time has elapsed:
p.stuckTime = 90 + Math.random() * 20;
p.accelX = 0;
p.accelY = gravity;
p.accelZ = 0;
}
}
// update viewing angle
turnAngle = (turnAngle + turnSpeed) % (2 * Math.PI);
sinAngle = Math.sin(turnAngle);
cosAngle = Math.cos(turnAngle);
// background fill
context.fillStyle = '#000000';
context.fillRect(0, 0, displayWidth, displayHeight);
// update and draw particles
p = particleList.first;
while (p != null) {
// before list is altered record next particle
nextParticle = p.next;
// update age
p.age++;
// if the particle is past its 'stuck' time, it will begin to move.
if (p.age > p.stuckTime) {
p.velX += p.accelX + randAccelX * (Math.random() * 2 - 1);
p.velY += p.accelY + randAccelY * (Math.random() * 2 - 1);
p.velZ += p.accelZ + randAccelZ * (Math.random() * 2 - 1);
p.x += p.velX;
p.y += p.velY;
p.z += p.velZ;
}
/*
We are doing two things here to calculate display coordinates.
The whole display is being rotated around a vertical axis, so we first calculate rotated coordinates for
x and z (but the y coordinate will not change).
Then, we take the new coordinates (rotX, y, rotZ), and project these onto the 2D view plane.
*/
rotX = cosAngle * p.x + sinAngle * (p.z - sphereCenterZ);
rotZ = -sinAngle * p.x + cosAngle * (p.z - sphereCenterZ) + sphereCenterZ;
// m = this.radius_sp * fLen / (fLen - rotZ);
m = this.radius_sp;
p.projX = rotX * m + projCenterX;
p.projY = p.y * m + projCenterY;
p.projZ = rotZ * m + projCenterX;
// update alpha according to envelope parameters.
if (p.age < p.attack + p.hold + p.decay) {
if (p.age < p.attack) {
p.alpha = (p.holdValue - p.initValue) / p.attack * p.age + p.initValue;
} else if (p.age < p.attack + p.hold) {
p.alpha = p.holdValue;
} else if (p.age < p.attack + p.hold + p.decay) {
p.alpha = (p.lastValue - p.holdValue) / p.decay * (p.age - p.attack - p.hold) + p.holdValue;
}
} else {
p.dead = true;
}
// see if the particle is still within the viewable range.
if ((p.projX > displayWidth) || (p.projX < 0) || (p.projY < 0) || (p.projY > displayHeight) || (rotZ > zMax)) {
outsideTest = true;
} else {
outsideTest = false;
}
if (outsideTest || p.dead ||
(p.projX > displayWidth / (2 + (1 - Math.random())) && p.projZ + displayWidth * 0.1 > displayWidth / 2) ||
(p.projX < displayWidth / (2 - (1 - Math.random())) && p.projZ + displayWidth * 0.25 < displayWidth / 2)
) {
recycle(p);
} else {
// depth-dependent darkening
// console.log(turnAngle, rotZ)
depthAlphaFactor = 1;
// depthAlphaFactor = (1 - (1.5 + rotZ / 100));
depthAlphaFactor = (depthAlphaFactor > 1) ? 1 : ((depthAlphaFactor < 0) ? 0 : depthAlphaFactor);
context.fillStyle = rgbString + depthAlphaFactor * p.alpha + ')';
// draw
context.beginPath();
context.arc(p.projX, p.projY, m * particleRad, 0, 2 * Math.PI, false);
context.closePath();
context.fill();
}
p = nextParticle;
}
window.requestAnimationFrame(onTimer);
}
const addParticle = (x0, y0, z0, vx0, vy0, vz0) => {
let newParticle;
// const color;
// check recycle bin for available drop:
if (recycleBin.first != null) {
newParticle = recycleBin.first;
// remove from bin
if (newParticle.next != null) {
recycleBin.first = newParticle.next;
newParticle.next.prev = null;
} else {
recycleBin.first = null;
}
} else {
newParticle = {};
}
// if the recycle bin is empty, create a new particle (a new empty object):
// add to beginning of particle list
if (particleList.first == null) {
particleList.first = newParticle;
newParticle.prev = null;
newParticle.next = null;
} else {
newParticle.next = particleList.first;
particleList.first.prev = newParticle;
particleList.first = newParticle;
newParticle.prev = null;
}
// initialize
newParticle.x = x0;
newParticle.y = y0;
newParticle.z = z0;
newParticle.velX = vx0;
newParticle.velY = vy0;
newParticle.velZ = vz0;
newParticle.age = 0;
newParticle.dead = false;
if (Math.random() < 0.5) {
newParticle.right = true;
} else {
newParticle.right = false;
}
return newParticle;
}
const recycle = (p) => {
// remove from particleList
if (particleList.first === p) {
if (p.next != null) {
p.next.prev = null;
particleList.first = p.next;
} else {
particleList.first = null;
}
} else {
if (p.next == null) {
p.prev.next = null;
} else {
p.prev.next = p.next;
p.next.prev = p.prev;
}
}
// add to recycle bin
if (recycleBin.first == null) {
recycleBin.first = p;
p.prev = null;
p.next = null;
} else {
p.next = recycleBin.first;
recycleBin.first.prev = p;
recycleBin.first = p;
p.prev = null;
}
};
init();
}
}
So I will be happy with any help also REWARD(for full implementation) is possible (ETH, BTC any currency you wish).
I'm using nearest neighbor algorithm to zoom the image on canvas. But, when I move the scaling bar higher, the image have white line that create a square array
Original Image
After I move the scale bar
The zoom is work but the problem is only the white lines.
For the source code I will provide in bottom
1.html
<!DOCTYPE HTML>
<html>
<head>
<title>Prototype PC</title>
</head>
<body>
<canvas id='canvas1'></canvas>
<hr>
<button id='read'>READ IMAGE</button>
<hr>
Scale <input type='range' value='1' min='1' max='5' step='0.25' id='scale'>
<br><button id='default2'>Default Scalling</button>
<hr/>
</body>
<style>
body{
background : rgba(255,255,255,1);
}
</style>
<script src='imagine.js'></script>
<script>
var canvas = document.getElementById('canvas1')
var obj = new pc(canvas)
obj.image2canvas("565043_553561101348179_1714194038_a.jpg")
var tes = new Array()
document.getElementById('read').addEventListener('click',function(){
tes = obj.image2read()
})
document.getElementById('scale').addEventListener('change',function(){
var scaleval = this.value
var xpos = 0
var ypos = 0
var xnow = 0
var ynow = 0
var objW = obj.width
var objH = obj.height
tesbackup = new Array()
for(var c=0; c<tes.length; c++){
temp = new Array()
for(var d=0; d<4; d++){
temp.push(255)
}
tesbackup.push(temp)
}
//end of copy
for(var i=0; i<tes.length; i++){
xpos = obj.i2x(i)
ypos = obj.i2y(i)
xnow = Math.round(xpos) * scaleval)
ynow = Math.round(ypos) * scaleval)
if (xnow < objW && ynow < objH) {
for (var j=0; j<scaleval; j++) {
for (var k=0; k<scaleval; k++) {
var idxnow = obj.xy2i(xnow,ynow)
tesbackup[idxnow][0] = tes[i][0]
tesbackup[idxnow][1] = tes[i][1]
tesbackup[idxnow][2] = tes[i][2]
}
}
}
}
obj.array2canvas(tesbackup)
})
</script>
and, for imagine.js
function info(text){
console.info(text)
}
function pc(canvas){
this.canvas = canvas
this.context = this.canvas.getContext('2d')
this.width = 0
this.height = 0
this.imgsrc = ""
this.image2read = function(){
this.originalLakeImageData = this.context.getImageData(0,0, this.width, this.height)
this.resultArr = new Array()
this.tempArr = new Array()
this.tempCount = 0
for(var i=0; i<this.originalLakeImageData.data.length; i++){
this.tempCount++
this.tempArr.push(this.originalLakeImageData.data[i])
if(this.tempCount == 4){
this.resultArr.push(this.tempArr)
this.tempArr = []
this.tempCount = 0
}
}
info('image2read Success ('+this.imgsrc+') : '+this.width+'x'+this.height)
return this.resultArr
}
this.image2canvas = function(imgsrc){
var imageObj = new Image()
var parent = this
imageObj.onload = function() {
parent.canvas.width = imageObj.width
parent.canvas.height = imageObj.height
parent.context.drawImage(imageObj, 0, 0)
parent.width = imageObj.width
parent.height = imageObj.height
info('image2canvas Success ('+imgsrc+')')
}
imageObj.src = imgsrc
this.imgsrc = imgsrc
}
this.array2canvas = function(arr){
this.imageData = this.context.getImageData(0,0, this.width, this.height)
if(this.imageData.data.length != arr.length*4) {
return false
}
for(var i = 0; i < arr.length; i++){
this.imageData.data[(i*4)] = arr[i][0]
this.imageData.data[(i*4)+1] = arr[i][1]
this.imageData.data[(i*4)+2] = arr[i][2]
this.imageData.data[(i*4)+3] = arr[i][3]
}
this.context.clearRect(0, 0, this.width, this.height)
this.context.putImageData(this.imageData, 0, 0)
info('Array2Canvas Success ('+this.imgsrc+')')
}
this.i2x = function(i){
return (i % this.width)
}
this.i2y = function(i){
return ((i - (i % this.width))/ this.width)
}
this.xy2i = function(x,y){
return (y * this.width) + (x)
}
}
Thanks in advance for a solution of this problem
Rounding out pixels
Nearest pixel will result in some zoomed pixels being larger than otheres
It is a problem with the value of scaleval. It has a step of 0.25 and when you calculate each zoomed pixels address you use (and I am guessing as your code has syntax errors) Math.round(xpos * scaleval) but then you draw the pixel using only the fractional size eg 2.75 not the integer size eg 3.0
The size of each pixel is var xSize = Math.round((xpos + 1) * scaleval)-Math.round(xpos * scaleval) same for y. That way when the pixel zoom is not an integer value every so many zoomed pixels will be one pixel wider and higher.
The following is a fix of your code but as you had a number of syntax errors and bugs I have had to guess some of your intentions.
xpos = obj.i2x(i)
ypos = obj.i2y(i)
xnow = Math.round(xpos * scaleval)
ynow = Math.round(ypos * scaleval)
// pixel width and height
var pw = Math.round((xpos + 1) * scaleval) - xnow;
var ph = Math.round((ypos + 1) * scaleval) - ynow;
if (xnow < objW && ynow < objH) {
for (var y = 0; y < ph; y++) {
for (var x =0; x < pw; x++) {
var idxnow = obj.xy2i(xnow + x, ynow + y)
tesbackup[idxnow][0] = tes[i][0]
tesbackup[idxnow][1] = tes[i][1]
tesbackup[idxnow][2] = tes[i][2]
}
}
}
}
But you are not really doing a nearest neighbor algorithm. For that you iterate each of the destination pixels finding the nearest pixel and using its colour. That allows you to easily apply a transform to the zoom but still get every pixel and not skip pixels due to rounding errors.
Nearest neighbor
Example of using nearest neighbor lookup for a scale rotated and translated image
var scaleFac = 2.3; // scale 1> zoom in
var panX = 10; // scaled image pan
var panY = 10;
var ang = 1;
var w = ctx.canvas.width; // source image
var h = ctx.canvas.height;
var wd = ctx1.canvas.width; // destination image
var hd = ctx1.canvas.height;
// use 32bit ints as we are not interested in the channels
var src = ctx.getImageData(0, 0, w, h);
var data = new Uint32Array(src.data.buffer);// source
var dest = ctx1.createImageData(wd, hd);
var zoomData = new Uint32Array(dest.data.buffer);// destination
var xdx = Math.cos(ang) * scaleFac; // xAxis vector x
var xdy = Math.sin(ang) * scaleFac; // xAxis vector y
var ind = 0;
var xx,yy;
for(var y = 0; y < hd; y ++){
for(var x = 0; x < wd; x ++){
// transform point
xx = (x * xdx - y * xdy + panX);
yy = (x * xdy + y * xdx + panY);
// is the lookup pixel in bounds
if(xx >= 0 && xx < w && yy >= 0 && yy < h){
// use the nearest pixel to set the new pixel
zoomData[ind++] = data[(xx | 0) + (yy | 0) * w]; // set the pixel
}else{
zoomData[ind++] = 0; // pixels outside bound are transparent
}
}
}
ctx1.putImageData(dest, 0, 0); // put the pixels onto the destination canvas
As on the attached fiddle, the background image on the canvas is just coming and getting disappearing
I tried both createPattern and drawImage both are having same issue.
I am not an expert in Canvas. Any help would be appreciated
(function(){
var canvas = document.getElementById('c'),
/** #type {CanvasRenderingContext2D} */
ctx = canvas.getContext('2d'),
width = 400,
height = 400,
half_width = width >> 1,
half_height = height >> 1,
size = width * (height + 2) * 2,
delay = 30,
oldind = width,
newind = width * (height + 3),
riprad = 3,
ripplemap = [],
last_map = [],
ripple,
texture,
line_width = 20,
step = line_width * 2,
count = height / line_width;
canvas.width = width;
canvas.height = height;
/*
* Water ripple demo can work with any bitmap image
*/
var imageObj = new Image();
imageObj.onload = function() {
var pattern = ctx.createPattern(imageObj, 'repeat');
ctx.rect(0, 0, width, height);
ctx.fillStyle = pattern;
ctx.fill();
ctx.save();
};
imageObj.src = 'http://www.html5canvastutorials.com/demos/assets/wood-pattern.png';
with (ctx) {
fillStyle = '#ccc';
fillRect(0, 0, width, height);
fillStyle = '#999999';
save();
rotate(-0.785);
for (var i = 0; i < count; i++) {
fillRect(-width, i * step, width * 3, line_width);
}
}
texture = ctx.getImageData(0, 0, width, height);
ripple = ctx.getImageData(0, 0, width, height);
for (var i = 0; i < size; i++) {
last_map[i] = ripplemap[i] = 0;
}
/**
* Main loop
*/
function run() {
newframe();
ctx.putImageData(ripple, 0, 0);
}
/**
* Disturb water at specified point
*/
function disturb(dx, dy) {
dx <<= 0;
dy <<= 0;
for (var j = dy - riprad; j < dy + riprad; j++) {
for (var k = dx - riprad; k < dx + riprad; k++) {
ripplemap[oldind + (j * width) + k] += 128;
}
}
}
/**
* Generates new ripples
*/
function newframe() {
var a, b, data, cur_pixel, new_pixel, old_data;
var t = oldind; oldind = newind; newind = t;
var i = 0;
// create local copies of variables to decrease
// scope lookup time in Firefox
var _width = width,
_height = height,
_ripplemap = ripplemap,
_last_map = last_map,
_rd = ripple.data,
_td = texture.data,
_half_width = half_width,
_half_height = half_height;
for (var y = 0; y < _height; y++) {
for (var x = 0; x < _width; x++) {
var _newind = newind + i, _mapind = oldind + i;
data = (
_ripplemap[_mapind - _width] +
_ripplemap[_mapind + _width] +
_ripplemap[_mapind - 1] +
_ripplemap[_mapind + 1]) >> 1;
data -= _ripplemap[_newind];
data -= data >> 5;
_ripplemap[_newind] = data;
//where data=0 then still, where data>0 then wave
data = 1024 - data;
old_data = _last_map[i];
_last_map[i] = data;
if (old_data != data) {
//offsets
a = (((x - _half_width) * data / 1024) << 0) + _half_width;
b = (((y - _half_height) * data / 1024) << 0) + _half_height;
//bounds check
if (a >= _width) a = _width - 1;
if (a < 0) a = 0;
if (b >= _height) b = _height - 1;
if (b < 0) b = 0;
new_pixel = (a + (b * _width)) * 4;
cur_pixel = i * 4;
_rd[cur_pixel] = _td[new_pixel];
_rd[cur_pixel + 1] = _td[new_pixel + 1];
_rd[cur_pixel + 2] = _td[new_pixel + 2];
}
++i;
}
}
}
canvas.onmousemove = function(/* Event */ evt) {
disturb(evt.offsetX || evt.layerX, evt.offsetY || evt.layerY);
};
setInterval(run, delay);
// generate random ripples
var rnd = Math.random;
var timeOut;
var intrvl = setInterval(function() {
clearTimeout(timeOut);
disturb(0, (height/40));
disturb((width/2.67), (height/40));
disturb((width/1.33), (height/40));
disturb(0, (height/2.67));
disturb((width/2.67), (height/2.67));
disturb((width/1.33), (height/2.67));
disturb(0, (height/1.33));
disturb((width/2.67), (height/1.33));
disturb((width/1.33), (height/1.33));
timeOut= setTimeout(function(){
disturb((width/1.8), (height/8));
disturb((width/-1.2), (height/8));
disturb((width/1.14), (height/8));
disturb((width/1.8), (height/2.13));
disturb((width/-1.2), (height/2.13));
disturb((width/1.14), (height/2.13));
disturb((width/1.8), (height/1.03));
disturb((width/-1.2), (height/1.03));
disturb((width/1.14), (height/1.03));;
},300);
}, 700);
setTimeout(function(){
clearInterval(intrvl);
},3000);
})();
this is the link to the fiddle
Having to give the idea of an ever changing network of nodes (each with different impact and possibly more than one color) connecting each other to create something.
I wanted to give it depth perception, so I ended up using two canvases around the title: one in the foreground, even over the words, and the other in background, with slightly larger and blurred elements.
Demo here, full JavaScript code at the moment:
// min and max radius, radius threshold and percentage of filled circles
var radMin = 5,
radMax = 125,
filledCircle = 60, //percentage of filled circles
concentricCircle = 30, //percentage of concentric circles
radThreshold = 25; //IFF special, over this radius concentric, otherwise filled
//min and max speed to move
var speedMin = 0.3,
speedMax = 2.5;
//max reachable opacity for every circle and blur effect
var maxOpacity = 0.6;
//default palette choice
var colors = ['52,168,83', '117,95,147', '199,108,23', '194,62,55', '0,172,212', '120,120,120'],
bgColors = ['52,168,83', '117,95,147', '199,108,23', '194,62,55', '0,172,212', '120,120,120'],
circleBorder = 10,
backgroundLine = bgColors[0];
var backgroundMlt = 0.85;
//min distance for links
var linkDist = Math.min(canvas.width, canvas.height) / 2.4,
lineBorder = 2.5;
//most importantly: number of overall circles and arrays containing them
var maxCircles = 12,
points = [],
pointsBack = [];
//populating the screen
for (var i = 0; i < maxCircles * 2; i++) points.push(new Circle());
for (var i = 0; i < maxCircles; i++) pointsBack.push(new Circle(true));
//experimental vars
var circleExp = 1,
circleExpMax = 1.003,
circleExpMin = 0.997,
circleExpSp = 0.00004,
circlePulse = false;
//circle class
function Circle(background) {
//if background, it has different rules
this.background = (background || false);
this.x = randRange(-canvas.width / 2, canvas.width / 2);
this.y = randRange(-canvas.height / 2, canvas.height / 2);
this.radius = background ? hyperRange(radMin, radMax) * backgroundMlt : hyperRange(radMin, radMax);
this.filled = this.radius < radThreshold ? (randint(0, 100) > filledCircle ? false : 'full') : (randint(0, 100) > concentricCircle ? false : 'concentric');
this.color = background ? bgColors[randint(0, bgColors.length - 1)] : colors[randint(0, colors.length - 1)];
this.borderColor = background ? bgColors[randint(0, bgColors.length - 1)] : colors[randint(0, colors.length - 1)];
this.opacity = 0.05;
this.speed = (background ? randRange(speedMin, speedMax) / backgroundMlt : randRange(speedMin, speedMax)); // * (radMin / this.radius);
this.speedAngle = Math.random() * 2 * Math.PI;
this.speedx = Math.cos(this.speedAngle) * this.speed;
this.speedy = Math.sin(this.speedAngle) * this.speed;
var spacex = Math.abs((this.x - (this.speedx < 0 ? -1 : 1) * (canvas.width / 2 + this.radius)) / this.speedx),
spacey = Math.abs((this.y - (this.speedy < 0 ? -1 : 1) * (canvas.height / 2 + this.radius)) / this.speedy);
this.ttl = Math.min(spacex, spacey);
};
Circle.prototype.init = function() {
Circle.call(this, this.background);
}
//support functions
//generate random int a<=x<=b
function randint(a, b) {
return Math.floor(Math.random() * (b - a + 1) + a);
}
//generate random float
function randRange(a, b) {
return Math.random() * (b - a) + a;
}
//generate random float more likely to be close to a
function hyperRange(a, b) {
return Math.random() * Math.random() * Math.random() * (b - a) + a;
}
//rendering function
function drawCircle(ctx, circle) {
//circle.radius *= circleExp;
var radius = circle.background ? circle.radius *= circleExp : circle.radius /= circleExp;
ctx.beginPath();
ctx.arc(circle.x, circle.y, radius * circleExp, 0, 2 * Math.PI, false);
ctx.lineWidth = Math.max(1, circleBorder * (radMin - circle.radius) / (radMin - radMax));
ctx.strokeStyle = ['rgba(', circle.borderColor, ',', circle.opacity, ')'].join('');
if (circle.filled == 'full') {
ctx.fillStyle = ['rgba(', circle.borderColor, ',', circle.background ? circle.opacity * 0.8 : circle.opacity, ')'].join('');
ctx.fill();
ctx.lineWidth=0;
ctx.strokeStyle = ['rgba(', circle.borderColor, ',', 0, ')'].join('');
}
ctx.stroke();
if (circle.filled == 'concentric') {
ctx.beginPath();
ctx.arc(circle.x, circle.y, radius / 2, 0, 2 * Math.PI, false);
ctx.lineWidth = Math.max(1, circleBorder * (radMin - circle.radius) / (radMin - radMax));
ctx.strokeStyle = ['rgba(', circle.color, ',', circle.opacity, ')'].join('');
ctx.stroke();
}
circle.x += circle.speedx;
circle.y += circle.speedy;
if (circle.opacity < (circle.background ? maxOpacity : 1)) circle.opacity += 0.01;
circle.ttl--;
}
//initializing function
function init() {
window.requestAnimationFrame(draw);
}
//rendering function
function draw() {
if (circlePulse) {
if (circleExp < circleExpMin || circleExp > circleExpMax) circleExpSp *= -1;
circleExp += circleExpSp;
}
var ctxfr = document.getElementById('canvas').getContext('2d');
var ctxbg = document.getElementById('canvasbg').getContext('2d');
ctxfr.globalCompositeOperation = 'destination-over';
ctxfr.clearRect(0, 0, canvas.width, canvas.height); // clear canvas
ctxbg.globalCompositeOperation = 'destination-over';
ctxbg.clearRect(0, 0, canvas.width, canvas.height); // clear canvas
ctxfr.save();
ctxfr.translate(canvas.width / 2, canvas.height / 2);
ctxbg.save();
ctxbg.translate(canvas.width / 2, canvas.height / 2);
//function to render each single circle, its connections and to manage its out of boundaries replacement
function renderPoints(ctx, arr) {
for (var i = 0; i < arr.length; i++) {
var circle = arr[i];
//checking if out of boundaries
if (circle.ttl<0) {}
var xEscape = canvas.width / 2 + circle.radius,
yEscape = canvas.height / 2 + circle.radius;
if (circle.ttl < -20) arr[i].init(arr[i].background);
//if (Math.abs(circle.y) > yEscape || Math.abs(circle.x) > xEscape) arr[i].init(arr[i].background);
drawCircle(ctx, circle);
}
for (var i = 0; i < arr.length - 1; i++) {
for (var j = i + 1; j < arr.length; j++) {
var deltax = arr[i].x - arr[j].x;
var deltay = arr[i].y - arr[j].y;
var dist = Math.pow(Math.pow(deltax, 2) + Math.pow(deltay, 2), 0.5);
//if the circles are overlapping, no laser connecting them
if (dist <= arr[i].radius + arr[j].radius) continue;
//otherwise we connect them only if the dist is < linkDist
if (dist < linkDist) {
var xi = (arr[i].x < arr[j].x ? 1 : -1) * Math.abs(arr[i].radius * deltax / dist);
var yi = (arr[i].y < arr[j].y ? 1 : -1) * Math.abs(arr[i].radius * deltay / dist);
var xj = (arr[i].x < arr[j].x ? -1 : 1) * Math.abs(arr[j].radius * deltax / dist);
var yj = (arr[i].y < arr[j].y ? -1 : 1) * Math.abs(arr[j].radius * deltay / dist);
ctx.beginPath();
ctx.moveTo(arr[i].x + xi, arr[i].y + yi);
ctx.lineTo(arr[j].x + xj, arr[j].y + yj);
var samecolor = arr[i].color == arr[j].color;
ctx.strokeStyle = ["rgba(", arr[i].borderColor, ",", Math.min(arr[i].opacity, arr[j].opacity) * ((linkDist - dist) / linkDist), ")"].join("");
ctx.lineWidth = (arr[i].background ? lineBorder * backgroundMlt : lineBorder) * ((linkDist - dist) / linkDist); //*((linkDist-dist)/linkDist);
ctx.stroke();
}
}
}
}
var startTime = Date.now();
renderPoints(ctxfr, points);
renderPoints(ctxbg, pointsBack);
deltaT = Date.now() - startTime;
ctxfr.restore();
ctxbg.restore();
window.requestAnimationFrame(draw);
}
init();
I asked around and ctx.save() and ctx.restore() are in the top list of suspects, but I wouldn't know how to do this without them.
This is my first animation with canvas, which AFAIK should have been the best option in terms of cross-browser support and (decent) performances, but any advice on this side is still welcome; also, seems to slow down significantly on FF, but just on some machines where hardware acceleration does not work properly (or at all).
From what I read here (and basically everywhere else), FF seems to have serious issues dealing with canvas, but maybe I can optimize things a bit more.
Should I use something other than canvas to do the animation? But also consider that other options (like using SVG) seem to have less support, not to mention it would mean redoing most of the work.
Notes: The first part with the general variables might not be the best practice, but it worked to let a non-technical staff member (UI designer) play on the variables to see different results.
I have two questions, the first being how do I access the indexes within my array separately, because my console.log of [n][0] results in two values - x and y. Secondly, for the butterfly curve, https://en.wikipedia.org/wiki/Butterfly_curve_%28transcendental%29, how would I determine the values of t? and reiterate through a certain minimum and maximum. In need of logic support.
Here's my progress so far.
/*function drawButterFly(n){
c.beginPath();
console.log(n[2])
for (var i = 0; i < n.length; i++){
if (i === 0) {
c.moveTo();
} else {
c.lineTo();
}
c.stroke();
}
}*/
function butterFly() {
var r = 5;
var N = 3;
var value = [];
for (var a = 0.2; a < 2*Math.PI; a = a + 0.1){
value.push(a);
}
var t = value[Math.floor(Math.random()*value.length)];
var cos = r*Math.cos(t)*( (Math.exp(Math.cos(t))) - (2*Math.cos(4*t)) - (Math.sin(t/12)^5) );
var sin = r*Math.sin(t)*( (Math.exp(Math.cos(t))) - (2*Math.cos(4*t)) - (Math.sin(t/12)^5) );
var n = [];
for (var u = 0; u < N; u++){
var x = sin * -u;
var y = cos * -u;
n.push([x,y]);
}
drawButterFly(n);
}
Since you're pushing an array here: n.push([x,y]) you can access the x component of the first element with n[0][0] and the y component of the same element with n[0][1]
Example:
var n = [];
n.push( ["x", "y"] );
console.log( n[0][0] );
console.log( n[0][1] );
As for the useful values of t - in the image you've shown, you'll notice that the same butterfly is drawn several times at different sizes. To draw a complete butterfly, you need to use the range for t of [0..2pi]. If you want to draw two butterflies, you need to use the range [0..4pi]. That is it's cyclic over the same period that a circle is. Unlike a circle however, each cycle doesn't draw over the previous one.
Here's a quick and nasty example:
function byId(id) {
return document.getElementById(id);
}
window.addEventListener('load', onDocLoaded, false);
function onDocLoaded(evt) {
butterFly();
}
function butterFly() {
var pointArray = [];
var stepSize = 0.05; // ~125 steps for every 360°
var upperLimit = 4 * Math.PI;
var scale = 20;
for (var t = 0.0; t < upperLimit; t += stepSize) {
var xVal = Math.sin(t) * ((Math.exp(Math.cos(t))) - (2 * Math.cos(4 * t)) - (Math.pow(Math.sin(t / 12), 5)));
var yVal = Math.cos(t) * ((Math.exp(Math.cos(t))) - (2 * Math.cos(4 * t)) - (Math.pow(Math.sin(t / 12), 5)));
pointArray.push([scale * xVal, -scale * yVal]); // -1 value since screen-y direction is opposite direction to cartesian coords y
}
drawButterFly(pointArray);
}
function drawButterFly(pointArray) {
var can = byId('myCan');
var ctx = can.getContext('2d');
var originX, originY;
originX = can.width / 2;
originY = can.height / 2;
ctx.beginPath();
for (var i = 0; i < pointArray.length; i++) {
if (i === 0) {
ctx.moveTo(originX + pointArray[i][0], originX + pointArray[i][1]);
} else {
ctx.lineTo(originX + pointArray[i][0], originY + pointArray[i][1]);
}
}
ctx.closePath();
ctx.stroke();
}
canvas {
border: solid 1px red;
}
<canvas id='myCan' width='256' height='256' />
If I'm not mistaken, the Butterfly curve is given as a pair of parametric equations, meaning you increment t to get the next (x, y) points on your curve. In other words, your t is what you should be using in place of u in your code, and the range of values for t should be 0 .. 24*pi as that's the range in which sin(t / 12) has its unique values).
Here's a version that demonstrates the drawing of the curve to a canvas:
function getPoint(t, S, O) {
var cos_t = Math.cos(t);
var factor = Math.exp(cos_t) - 2 * Math.cos(4*t) - Math.pow(Math.sin(t/12), 5);
return {
x: S * Math.sin(t) * factor + O.x,
y: S * cos_t * factor + O.y
};
}
var canvas = document.getElementById("c");
canvas.width = 300;
canvas.height = 300;
var ctx = canvas.getContext("2d");
// First path
ctx.beginPath();
ctx.strokeStyle = 'blue';
var offset = {x:150, y:120};
var scale = 40;
var maxT = 24 * Math.PI;
var p = getPoint(0, scale, offset);
ctx.moveTo(p.x, canvas.height - p.y);
for (var t = 0.01; t <= maxT; t += 0.01) {
p = getPoint(t, scale, offset);
ctx.lineTo(p.x, canvas.height - p.y);
}
ctx.stroke();
#c {
border: solid 1px black;
}
<canvas id="c"></canvas>
One thing to note: canvases have y = 0 start at the top, so you need to inverse your y (i.e. canvas.height - y) to have your curve orient correctly.
UPDATE: Added animated version
As requested by royhowie, here's an animated version, using requestAnimationFrame:
function getPoint(t, S, O) {
var cos_t = Math.cos(t);
var factor = Math.exp(cos_t) - 2 * Math.cos(4*t) - Math.pow(Math.sin(t/12), 5);
return {
x: S * Math.sin(t) * factor + O.x,
y: S * cos_t * factor + O.y
};
}
var canvas = document.getElementById("c");
canvas.width = 300;
canvas.height = 300;
var ctx = canvas.getContext("2d");
var offset = {x:150, y:120};
var scale = 40;
var maxT = 24 * Math.PI;
var animationID;
var started = false;
var t = 0;
document.getElementById('start').addEventListener('click', function(e) {
e.preventDefault();
if (!started) {
animationID = requestAnimationFrame(animate);
started = true;
}
});
document.getElementById('pause').addEventListener('click', function(e) {
e.preventDefault();
if (started) {
cancelAnimationFrame(animationID);
started = false;
}
});
function animate() {
animationID = requestAnimationFrame(animate);
var p = getPoint(t, scale, offset);
if (t === 0) {
ctx.beginPath();
ctx.strokeStyle = 'blue';
ctx.moveTo(p.x, canvas.height - p.y);
t += 0.01;
} else if (t < maxT) {
ctx.lineTo(p.x, canvas.height - p.y);
ctx.stroke();
t += 0.01;
} else {
cancelAnimationFrame(animationID);
}
}
#c {
border: solid 1px black;
}
<div>
<button id="start">Start</button>
<button id="pause">Pause</button>
</div>
<canvas id="c"></canvas>
Question 1
For an arbitrary integer i, let n[i] = [xi, yi]. xi can then be accessed via n[i][0] and yi via n[i][1]
Question 2
For values of t, I am sure you're gonna want to use sub-integer values, so I recommend using a constant increment value representing the "resolution" of your graph.
Let's call it dt. Also, I'd advise changing your variable names from single letters to something more descriptive, like min_t and max_t, and instead of n I'm going to call your array points.
function drawButterFly(points){
for (var i = 0, n = points.count; i < n; ++i) {
var x = points[i][0];
var y = points[i][1];
...
}
}
function butterFly(min_t, max_t, dt, r) {
var points = [];
for (var t = min_t; t < max_t; t+=dt){
var x = r*Math.sin(t)*...
var y = r*Math.cos(t)*...
points.push([x,y]);
}
drawButterFly(points, dt);
}
I'm not sure what the other loop inside of that function was for, but if you need it, you can adapt from the pattern above.
Usage example: butterFly(0, 10, 0.01, 3) -> t goes from 0 to 10 with an increment of 0.01, and r=3
Regarding your first question it's a better option to replace the multidimensional array containing the x and y coordinates with an object. Then when iterating over the array you can check for the object values.
So instead of:
n.push([x,y]);
you should do:
m.push({
'xPos' : x,
'yPos' : y
})
Later you can access this by m.xPos or m.yPos
Then you can access the x and y values by object literal names.
Regarding the second question: for a good pseudo code implementation of butterfly curves you might check Paul Burke site: http://paulbourke.net/geometry/butterfly/. So t in your case is:
t = i * 24.0 * PI / N;
As you see t is a parametric value which got incremented on each step when iterating over the array.