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I'm attempting to detect a canvas click and if the click coordinates match a shape. It works fine, the problem is that when the shapes overlap on the canvas (one shape might be smaller than the other) then both shapes are removed. Is there a way to avoid this and only remove one at a time?
addShape() {
const randomNum = (min, max) => Math.round(Math.random() * (max - min) + min),
randomRad = randomNum(10, 100),
randomX = randomNum(randomRad, this.canvas.width - randomRad);
let shape = new Shape(randomX, randomNum, randomRad);
shape.drawShape();
this.shapes.push(shape);
}
canvasClick() {
if(!this.paused) {
const canvasRect = event.target.getBoundingClientRect(),
clickedX = event.clientX - canvasRect.left,
clickedY = event.clientY - canvasRect.top;
for (let i = 0; i < this.shapes.length; i++) {
if(Math.pow(clickedX - this.shapes[i].x, 2) + Math.pow(clickedY - this.shapes[i].y, 2)
< Math.pow(this.shapes[i].rad,2)) {
this.shapes.splice(i, 1);
}
}
}
}
Thanks in advance for the help!
If I have understood what you what, the solution is pretty simple. Just break the loop after you remove one shape. Something like this:
for (let i = 0; i < this.shapes.length; i++) {
if (
Math.pow(clickedX - this.shapes[i].x, 2)
+ Math.pow(clickedY - this.shapes[i].y, 2)
< Math.pow(this.shapes[i].rad, 2)
) {
this.shapes.splice(i, 1);
break; // <--
}
}
You might also what to store the z position of shapes so that you can first sort them in the terms of z and then run this loop so that you don't remove shape below the clicked shape.
This is how I would do it. Please read the comments in the code. I am using the ctx.isPointInPath method but you may use the formula if you prefer.
The main idea is to exit the loop after finding and deleting the first circle.
I hope it helps.
let ctx = canvas.getContext("2d");
canvas.width = 300;
canvas.height = 300;
ctx.fillStyle = "rgba(0,0,0,.5)";
// the array of the circles
let circles = []
class Circle{
constructor(){
this.x = ~~(Math.random() * canvas.width);
this.y = ~~(Math.random() * canvas.height);
this.r = ~~(Math.random() * (40 - 10 + 1) + 10);
this.draw();
}
draw(){
ctx.beginPath();
ctx.arc(this.x,this.y, this.r, 0,2*Math.PI)
}
}
// create 20 circles
for(i=0;i<20;i++){
let c = new Circle();
ctx.fill()
circles.push(c)
}
canvas.addEventListener("click",(e)=>{
// detect the position of the mouse
let m = oMousePos(canvas, e)
for(let i=0;i<circles.length;i++){
// draw a circle but do not fill
circles[i].draw();
// check if the point is in path
if(ctx.isPointInPath(m.x,m.y)){
//remove the circle from the array
circles.splice(i, 1);
// clear the context
ctx.clearRect(0,0,canvas.width,canvas.height)
// redraw all the circles from the array
for(let j=0;j<circles.length;j++){
circles[j].draw();
ctx.fill()
}
//exit the loop
return;
}
}
})
// a function to detect the mouse position
function oMousePos(canvas, evt) {
var ClientRect = canvas.getBoundingClientRect();
return { //objeto
x: Math.round(evt.clientX - ClientRect.left),
y: Math.round(evt.clientY - ClientRect.top)
}
}
canvas{border:1px solid}
<canvas id="canvas"></canvas>
I have searched around but I can't find anything like what I'm trying to do that doesn't use Three.js in some way (I can't use Three.js because my computer is too old to support Webgl). Here's what I've got so far:
HTML:
<!DOCTYPE html>
<html>
<head>
<script type="text/javascript" src="terrain.js"></script>
<title>Terrain</title>
</head>
<body>
<canvas id="canvas" height="400" width="400"></canvas>
</body>
</html>
Javascript:
var canvas, ctx, row1 = [], row2 = [], intensity = 15, width = 20, height = 20, centery = 200, centerx = 200, minus, delta = 1.6, nu = .02;
window.onload = function() {
canvas = document.getElementById('canvas'), ctx = canvas.getContext('2d');
ctx.lineStyle = '#000'
for (var i = 0; i < height; i++) {
row2 = [];
minus = 200
for (var j = 0; j < width; j++) {
row2[j] = {
x: centerx - (minus * (delta * (nu * i))),
y: Math.floor(Math.random() * intensity) + (height * i)
}
minus -= height;
}
ctx.beginPath();
ctx.moveTo(row2[0].x,row2[0].y)
for (var k = 1; k < row2.length; k++) {
ctx.lineTo(row2[k].x,row2[k].y)
if (k == row2.length) {ctx.clostPath()}
}
ctx.stroke();
if (row1[0] && row2[0]) {
for (var l = 0; l < row2.length; l++) {
ctx.beginPath();
ctx.moveTo(row2[l].x,row2[l].y)
ctx.lineTo(row1[l].x,row1[l].y)
ctx.closePath();
ctx.stroke();
}
}
row1 = row2;
}
}
Currently, the result looks like a Christmas tree but I want it to look more like actual 3d wireframe terrain.
3D wire frame basics
3D can be done on any systems that can move pixels. Thought not by dedicated hardware Javascript can do alright if you are after simple 3d.
This answers shows how to create a mesh, rotate and move it, create a camera and move it, and project the whole lot onto the 2D canvas using simple moveTo, and lineTo calls.
This answer is a real rush job so apologies for the typos (if any) and messy code. Will clean it up in the come few days (if time permits). Any questions please do ask in the comments.
Update
I have not done any basic 3D for some time so having a little fun I have added to the answer with more comments in the code and added some extra functionality.
vec3 now has normalise, dot, cross functions.
mat now has lookat function and is ready for much more if needed.
mesh now maintains its own world matrix
Added box, and line that create box and line meshs
Created a second vector type vec3S (S for simple) that is just coordinates no functionality
Demo now shows how to add more objects, position them in the scene, use a lookat transform
Details about the code.
The code below is the basics of 3D. It has a mesh object to create objects out of 3D points (vertices) connected via lines.
Simple transformation for rotating, moving and scaling a model so it can be placed in the scene.
A very very basic camera that can only look forward, move up,down, left,right, in and out. And the focal length can be changed.
Only for lines as there is no depth sorting.
The demo does not clip to the camera front plane, but rather just ignores lines that have any part behind the camera;
You will have to work out the rest from the comments, 3D is a big subject and any one of the features is worth a question / answer all its own.
Oh and coordinates in 3D are origin in center of canvas. Y positive down, x positive right, and z positive into the screen. projection is basic so when you have perspective set to 400 than a object at 400 units out from camera will have a one to one match with pixel size.
var ctx = canvas.getContext("2d");
// some usage of vecs does not need the added functionality
// and will use the basic version
const vec3Basic = { x : 0, y : 0, z: 0};
const vec3Def = {
// Sets the vector scalars
// Has two signatures
// setVal(x,y,z) sets vector to {x,y,z}
// setVal(vec) set this vector to vec
setVal(x,y = x.y,z = x.z + (x = x.x) * 0){
this.x = x;
this.y = y;
this.z = z;
},
// subtract v from this vector
// Has two signatures
// setVal(v) subtract v from this returning a new vec3
// setVal(v,vec) subtract v from this returning result in retVec
sub(v,retVec = vec3()){
retVec.x = this.x - v.x;
retVec.y = this.y - v.y;
retVec.z = this.z - v.z;
return retVec;
},
// Cross product of two vectors this and v.
// Cross product can be thought of as get the vector
// that is perpendicular to the plane described by the two vector we are crossing
// Has two signatures
// cross(vec); // returns a new vec3 as the cross product of this and vec
// cross(vec, retVec); // set retVec as the cross product
cross (v, retVec = vec3()){
retVec.x = this.y * v.z - this.z * v.y;
retVec.y = this.z * v.x - this.x * v.z;
retVec.z = this.x * v.y - this.y * v.x;
return retVec;
},
// Dot product
// Dot product of two vectors if both normalized can be thought of as finding the cos of the angle
// between two vectors. If not normalised the dot product will give you < 0 if v points away from
// the plane that this vector is perpendicular to, if > 0 the v points in the same direction as the
// plane perpendicular to this vector. if 0 then v is at 90 degs to the plane this is perpendicular to
// Using vector dot on its self is the same as getting the length squared
// dot(vec3); // returns a number as a float
dot (v){ return this.x * v.x + this.y * v.y + this.z * this.z },
// normalize normalizes a vector. A normalized vector has length equale to 1 unit
// Has two signitures
// normalise(); normalises this vector returning this
// normalize(retVec); normalises this vector but puts the normalised vector in retVec returning
// returning retVec. Thiis is unchanged.
normalize(retVec = this){
// could have used len = this.dot(this) but for speed all functions will do calcs internaly
const len = Math.sqrt(this.x * this.x + this.y * this.y + this.z * this.z);
// it is assumed that all vector are valid (have length) so no test is made to avoid
// the divide by zero that will happen for invalid vectors.
retVec.x = this.x / len;
retVec.y = this.y / len;
retVec.z = this.z / len;
}
}
// Created as a singleton to close over working constants
const matDef = (()=>{
// to seed up vector math the following closed over vectors are used
// rather than create and dispose of vectors for every operation needing them
// Currently not used
const V1 = vec3();
return {
// The matrix is just 3 pointers one for each axis
// They represent the direction and scale in 3D of each axis
// when you transform a point x,y,z you move x along the x axis,
// then y along y and z along the z axis
xAxis : null,
yAxis : null,
zAxis : null,
// this is a position x,y,z and represents where in 3D space an objects
// center coordinate (0,0,0) will be. It is simply added to a point
// after it has been moved along the 3 axis.
pos : null,
// This function does most of the 3D work in most 3D environments.
// It rotates, scales, translates, and a whole lot more.
// It is a cut down of the full 4 by 4 3D matrix you will find in
// Libraries like three.js
transformVec3(vec,retVec = {}){
retVec.x = vec.x * this.xAxis.x + vec.y * this.yAxis.x + vec.z * this.zAxis.x + this.pos.x;
retVec.y = vec.x * this.xAxis.y + vec.y * this.yAxis.y + vec.z * this.zAxis.y + this.pos.y;
retVec.z = vec.x * this.xAxis.z + vec.y * this.yAxis.z + vec.z * this.zAxis.z + this.pos.z;
return retVec;
},
// resets the matrix
identity(){ // default matrix
this.xAxis.setVal(1,0,0); // x 1 unit long in the x direction
this.yAxis.setVal(0,1,0); // y 1 unit long in the y direction
this.zAxis.setVal(0,0,1); // z 1 unit long in the z direction
this.pos.setVal(0,0,0); // and position at the origin.
},
init(){ // need to call this before using due to the way I create these
// objects.
this.xAxis = vec3(1,0,0);
this.yAxis = vec3(0,1,0);
this.zAxis = vec3(0,0,1);
this.pos = vec3(0,0,0);
return this; // must have this line for the constructor function to return
},
setRotateY(amount){
var x = Math.cos(amount);
var y = Math.sin(amount);
this.xAxis.x = x;
this.xAxis.y = 0;
this.xAxis.z = y;
this.zAxis.x = -y;
this.zAxis.y = 0;
this.zAxis.z = x;
},
// creates a look at transform from the current position
// point is a vec3.
// No check is made to see if look at is at pos which will invalidate this matrix
// Note scale is lost in this operation.
lookAt(point){
// zAxis along vector from pos to point
this.pos.sub(point,this.zAxis).normalize();
// use y as vertical reference
this.yAxis.x = 0;
this.yAxis.y = 1;
this.yAxis.z = 0;
// get x axis perpendicular to the plane described by z and y axis
// need to normalise as z and y axis may not be at 90 deg
this.yAxis.cross(this.zAxis,this.xAxis).normalize();
// Get the y axis that is perpendicular to z and x axis
// Normalise is not really needed but rounding errors can be problematic
// so the normalise just fixes some of the rounding errors.
this.zAxis.cross(this.xAxis,this.yAxis).normalize();
},
}
})();
// Mesh object has buffers for the
// model as verts
// transformed mesh as tVerts
// projected 2D verts as dVerts (d for display)
// An a array of lines. Each line has two indexes that point to the
// vert that define their ends.
// Buffers are all preallocated to stop GC slowing everything down.
const meshDef = {
addVert(vec){
this.verts.push(vec);
// vec3(vec) in next line makes a copy of the vec. This is important
// as using the same vert in the two buffers will result in strange happenings.
this.tVerts.push(vec3S(vec)); // transformed verts pre allocated so GC does not bite
this.dVerts.push({x:0,y:0}); // preallocated memory for displaying 2d projection
// when x and y are zero this means that it is not visible
return this.verts.length - 1;
},
addLine(index1,index2){
this.lines.push(index1,index2);
},
transform(matrix = this.matrix){
for(var i = 0; i < this.verts.length; i++){
matrix.transformVec3(this.verts[i],this.tVerts[i]);
}
},
eachVert(callback){
for(var i = 0; i < this.verts.length; i++){
callback(this.tVerts[i],i);
}
},
eachLine(callback){
for(var i = 0; i < this.lines.length; i+= 2){
var ind1 = this.lines[i];
var v1 = this.dVerts[ind1]; // get the start
if(v1.x !== 0 && v1.y !== 0){ // is valid
var ind2 = this.lines[i+ 1]; // get end of line
var v2 = this.dVerts[ind2];
if(v2.x !== 0 && v2.y !== 0){ // is valid
callback(v1,v2);
}
}
}
},
init(){ // need to call this befor using
this.verts = [];
this.lines = [];
this.dVerts = [];
this.tVerts = [];
this.matrix = mat();
return this; // must have this line for the construtor function to return
}
}
const cameraDef = {
projectMesh(mesh){ // create a 2D mesh
mesh.eachVert((vert,i)=>{
var z = (vert.z + this.position.z);
if(z < 0){ // is behind the camera then ignor it
mesh.dVerts[i].x = mesh.dVerts[i].y = 0;
}else{
var s = this.perspective / z;
mesh.dVerts[i].x = (vert.x + this.position.x) * s;
mesh.dVerts[i].y = (vert.y + this.position.y) * s;
}
})
},
drawMesh(mesh){ // renders the 2D mesh
ctx.beginPath();
mesh.eachLine((v1,v2)=>{
ctx.moveTo(v1.x,v1.y);
ctx.lineTo(v2.x,v2.y);
})
ctx.stroke();
}
}
// vec3S creates a basic (simple) vector
// 3 signatures
//vec3S(); // return vec 1,0,0
//vec3S(vec); // returns copy of vec
//vec3S(x,y,z); // returns {x,y,z}
function vec3S(x = {x:1,y:0,z:0},y = x.y ,z = x.z + (x = x.x) * 0){ // a 3d point
return Object.assign({},vec3Basic,{x, y, z});
}
// vec3S creates a basic (simple) vector
// 3 signatures
//vec3S(); // return vec 1,0,0
//vec3S(vec); // returns copy of vec
//vec3S(x,y,z); // returns {x,y,z}
function vec3(x = {x:1,y:0,z:0},y = x.y ,z = x.z + (x = x.x) * 0){ // a 3d point
return Object.assign({},vec3Def,{x,y,z});
}
function mat(){ // matrix used to rotate scale and move a 3d point
return Object.assign({},matDef).init();
}
function mesh(){ // this is for storing objects as points in 3d and lines conecting points
return Object.assign({},meshDef).init();
}
function camera(perspective,position){ // this is for displaying 3D
return Object.assign({},cameraDef,{perspective,position});
}
// grid is the number of grids x,z and size is the overal size for x
function createLandMesh(gridx,gridz,size,maxHeight){
var m = mesh(); // create a mesh
var hs = size/2 ;
var step = size / gridx;
for(var z = 0; z < gridz; z ++){
for(var x = 0; x < gridx; x ++){
// create a vertex. Y is random
m.addVert(vec3S(x * step - hs, (Math.random() * maxHeight), z * step-hs)); // create a vert
}
}
for(var z = 0; z < gridz-1; z ++){
for(var x = 0; x < gridx-1; x ++){
if(x < gridx -1){ // dont go past end
m.addLine(x + z * gridx,x + 1 + z * gridx); // add line across
}
if(z < gridz - 1){ // dont go past end
m.addLine(x + z * (gridx-1),x + 1 + (z + 1) * (gridx-1));
}
}
}
return m;
}
function createBoxMesh(size){
var s = size / 2;
var m = mesh(); // create a mesh
// add bottom
m.addVert(vec3S(-s,-s,-s));
m.addVert(vec3S( s,-s,-s));
m.addVert(vec3S( s, s,-s));
m.addVert(vec3S(-s, s,-s));
// add top verts
m.addVert(vec3S(-s,-s, s));
m.addVert(vec3S( s,-s, s));
m.addVert(vec3S( s, s, s));
m.addVert(vec3S(-s, s, s));
// add lines
/// bottom lines
m.addLine(0,1);
m.addLine(1,2);
m.addLine(2,3);
m.addLine(3,0);
/// top lines
m.addLine(4,5);
m.addLine(5,6);
m.addLine(6,7);
m.addLine(7,4);
// side lines
m.addLine(0,4);
m.addLine(1,5);
m.addLine(2,6);
m.addLine(3,7);
return m;
}
function createLineMesh(v1 = vec3S(),v2 = vec3S()){
const m = mesh();
m.addVert(v1);
m.addVert(v2);
m.addLine(0,1);
return m;
}
//Create a land mesh grid 20 by 20 and 400 units by 400 units in size
var land = createLandMesh(20,20,400,20); // create a land mesh
var box = createBoxMesh(50);
var box1 = createBoxMesh(25);
var line = createLineMesh(); // line conecting boxes
line.tVerts[0] = box.matrix.pos; // set the line transformed tVect[0] to box matrix.pos
line.tVerts[1] = box1.matrix.pos; // set the line transformed tVect[0] to box1 matrix.pos
var cam = camera(200,vec3(0,0,0)); // create a projection with focal len 200 and at 0,0,0
box.matrix.pos.setVal(0,-100,400);
box1.matrix.pos.setVal(0,-100,400);
land.matrix.pos.setVal(0,100,300); // move down 100, move away 300
var w = canvas.width;
var h = canvas.height;
var cw = w / 2; // center of canvas
var ch = h / 2;
function update(timer){
// next section just maintains canvas size and resets state and clears display
if (canvas.width !== innerWidth || canvas.height !== innerHeight) {
cw = (w = canvas.width = innerWidth) /2;
ch = (h = canvas.height = innerHeight) /2;
}
ctx.setTransform(1,0,0,1,0,0); // reset transform
ctx.globalAlpha = 1; // reset alpha
ctx.fillStyle = "black";
ctx.fillRect(0,0,canvas.width,canvas.height);
// end of standard canvas maintenance
// render from center of canvas by setting canvas origin to center
ctx.setTransform(1,0,0,1,canvas.width / 2,canvas.height / 2)
land.matrix.setRotateY(timer/1000); // set matrix to rotation position
land.transform();
// move the blue box
var t = timer/1000;
box1.matrix.pos.setVal(Math.sin(t / 2.1) * 100,Math.sin( t / 3.2) * 100, Math.sin(t /5.3) * 90+300);
// Make the cyan box look at the blue box
box.matrix.lookAt(box1.matrix.pos);
// Transform boxes from local to world space
box1.transform();
box.transform();
// set camera x,y pos to mouse pos;
cam.position.x = mouse.x - cw;
cam.position.y = mouse.y - ch;
// move in and out
if (mouse.buttonRaw === 1) { cam.position.z -= 1 }
if (mouse.buttonRaw === 4) {cam.position.z += 1 }
// Converts mesh transformed verts to 2D screen coordinates
cam.projectMesh(land);
cam.projectMesh(box);
cam.projectMesh(box1);
cam.projectMesh(line);
// Draw each mesh in turn
ctx.strokeStyle = "#0F0";
cam.drawMesh(land);
ctx.strokeStyle = "#0FF";
cam.drawMesh(box);
ctx.strokeStyle = "#00F";
cam.drawMesh(box1);
ctx.strokeStyle = "#F00";
cam.drawMesh(line);
ctx.setTransform(1,0,0,1,cw,ch / 4);
ctx.font = "20px arial";
ctx.textAlign = "center";
ctx.fillStyle = "yellow";
ctx.fillText("Move mouse to move camera. Left right mouse move in out",0,0)
requestAnimationFrame(update);
}
requestAnimationFrame(update);
// A mouse handler from old lib of mine just to give some interaction
// not needed for the 3d
var mouse = (function () {
var m; // alias for mouse
var mouse = {
x : 0, y : 0, // mouse position
buttonRaw : 0,
buttonOnMasks : [0b1, 0b10, 0b100], // mouse button on masks
buttonOffMasks : [0b110, 0b101, 0b011], // mouse button off masks
bounds : null,
event(e) {
m.bounds = m.element.getBoundingClientRect();
m.x = e.pageX - m.bounds.left - scrollX;
m.y = e.pageY - m.bounds.top - scrollY;
if (e.type === "mousedown") { m.buttonRaw |= m.buttonOnMasks[e.which - 1] }
else if (e.type === "mouseup") { m.buttonRaw &= m.buttonOffMasks[e.which - 1] }
e.preventDefault();
},
start(element) {
m.element = element === undefined ? document : element;
"mousemove,mousedown,mouseup".split(",").forEach(name => document.addEventListener(name, mouse.event) );
document.addEventListener("contextmenu", (e) => { e.preventDefault() }, false);
return mouse;
},
}
m = mouse;
return mouse;
})().start(canvas);
canvas { position:absolute; top : 0px; left : 0px;}
<canvas id="canvas"></canvas>
I am visualising flight paths with D3 and Canvas. In short, I have data for each flight's origin and destination
as well as the airport coordinates. The ideal end state is to have an indiviudal circle representing a plane moving
along each flight path from origin to destination. The current state is that each circle gets visualised along the path,
yet the removal of the previous circle along the line does not work as clearRect gets called nearly constantly.
Current state:
Ideal state (achieved with SVG):
The Concept
Conceptually, an SVG path for each flight is produced in memory using D3's custom interpolation with path.getTotalLength() and path.getPointAtLength() to move the circle along the path.
The interpolator returns the points along the path at any given time of the transition. A simple drawing function takes these points and draws the circle.
Key functions
The visualisation gets kicked off with:
od_pairs.forEach(function(el, i) {
fly(el[0], el[1]); // for example: fly('LHR', 'JFK')
});
The fly() function creates the SVG path in memory and a D3 selection of a circle (the 'plane') - also in memory.
function fly(origin, destination) {
var pathElement = document.createElementNS(d3.namespaces.svg, 'path');
var routeInMemory = d3.select(pathElement)
.datum({
type: 'LineString',
coordinates: [airportMap[origin], airportMap[destination]]
})
.attr('d', path);
var plane = custom.append('plane');
transition(plane, routeInMemory.node());
}
The plane gets transitioned along the path by the custom interpolater in the delta() function:
function transition(plane, route) {
var l = route.getTotalLength();
plane.transition()
.duration(l * 50)
.attrTween('pointCoordinates', delta(plane, route))
// .on('end', function() { transition(plane, route); });
}
function delta(plane, path) {
var l = path.getTotalLength();
return function(i) {
return function(t) {
var p = path.getPointAtLength(t * l);
draw([p.x, p.y]);
};
};
}
... which calls the simple draw() function
function draw(coords) {
// contextPlane.clearRect(0, 0, width, height); << how to tame this?
contextPlane.beginPath();
contextPlane.arc(coords[0], coords[1], 1, 0, 2*Math.PI);
contextPlane.fillStyle = 'tomato';
contextPlane.fill();
}
This results in an extending 'path' of circles as the circles get drawn yet not removed as shown in the first gif above.
Full code here: http://blockbuilder.org/larsvers/8e25c39921ca746df0c8995cce20d1a6
My question is, how can I achieve to draw only a single, current circle while the previous circle gets removed without interrupting other circles being drawn on the same canvas?
Some failed attempts:
The natural answer is of course context.clearRect(), however, as there's a time delay (roughly a milisecond+) for each circle to be drawn as it needs to get through the function pipeline clearRect gets fired almost constantly.
I tried to tame the perpetual clearing of the canvas by calling clearRect only at certain intervals (Date.now() % 10 === 0 or the like) but that leads to no good either.
Another thought was to calculate the previous circle's position and remove the area specifically with a small and specific clearRect definition within each draw() function.
Any pointers very much appreciated.
Handling small dirty regions, especially if there is overlap between objects quickly becomes very computationally heavy.
As a general rule, a average Laptop/desktop can easily handle 800 animated objects if the computation to calculate position is simple.
This means that the simple way to animate is to clear the canvas and redraw every frame. Saves a lot of complex code that offers no advantage over the simple clear and redraw.
const doFor = (count,callback) => {var i=0;while(i < count){callback(i++)}};
function createIcon(drawFunc){
const icon = document.createElement("canvas");
icon.width = icon.height = 10;
drawFunc(icon.getContext("2d"));
return icon;
}
function drawPlane(ctx){
const cx = ctx.canvas.width / 2;
const cy = ctx.canvas.height / 2;
ctx.beginPath();
ctx.strokeStyle = ctx.fillStyle = "red";
ctx.lineWidth = cx / 2;
ctx.lineJoin = "round";
ctx.lineCap = "round";
ctx.moveTo(cx/2,cy)
ctx.lineTo(cx * 1.5,cy);
ctx.moveTo(cx,cy/2)
ctx.lineTo(cx,cy*1.5)
ctx.stroke();
ctx.lineWidth = cx / 4;
ctx.moveTo(cx * 1.7,cy * 0.6)
ctx.lineTo(cx * 1.7,cy*1.4)
ctx.stroke();
}
const planes = {
items : [],
icon : createIcon(drawPlane),
clear(){
planes.items.length = 0;
},
add(x,y){
planes.items.push({
x,y,
ax : 0, // the direction of the x axis of this plane
ay : 0,
dir : Math.random() * Math.PI * 2,
speed : Math.random() * 0.2 + 0.1,
dirV : (Math.random() - 0.5) * 0.01, // change in direction
})
},
update(){
var i,p;
for(i = 0; i < planes.items.length; i ++){
p = planes.items[i];
p.dir += p.dirV;
p.ax = Math.cos(p.dir);
p.ay = Math.sin(p.dir);
p.x += p.ax * p.speed;
p.y += p.ay * p.speed;
}
},
draw(){
var i,p;
const w = canvas.width;
const h = canvas.height;
for(i = 0; i < planes.items.length; i ++){
p = planes.items[i];
var x = ((p.x % w) + w) % w;
var y = ((p.y % h) + h) % h;
ctx.setTransform(-p.ax,-p.ay,p.ay,-p.ax,x,y);
ctx.drawImage(planes.icon,-planes.icon.width / 2,-planes.icon.height / 2);
}
}
}
const ctx = canvas.getContext("2d");
function mainLoop(){
if(canvas.width !== innerWidth || canvas.height !== innerHeight){
canvas.width = innerWidth;
canvas.height = innerHeight;
planes.clear();
doFor(800,()=>{ planes.add(Math.random() * canvas.width, Math.random() * canvas.height) })
}
ctx.setTransform(1,0,0,1,0,0);
// clear or render a background map
ctx.clearRect(0,0,canvas.width,canvas.height);
planes.update();
planes.draw();
requestAnimationFrame(mainLoop)
}
requestAnimationFrame(mainLoop)
canvas {
position : absolute;
top : 0px;
left : 0px;
}
<canvas id=canvas></canvas>
800 animated points
As pointed out in the comments some machines may be able to draw a circle if one colour and all as one path slightly quicker (not all machines). The point of rendering an image is that it is invariant to the image complexity. Image rendering is dependent on the image size but colour and alpha setting per pixel have no effect on rendering speed. Thus I have changed the circle to show the direction of each point via a little plane icon.
Path follow example
I have added a way point object to each plane that in the demo has a random set of way points added. I called it path (could have used a better name) and a unique path is created for each plane.
The demo is to just show how you can incorporate the D3.js interpolation into the plane update function. The plane.update now calls the path.getPos(time) which returns true if the plane has arrived. If so the plane is remove. Else the new plane coordinates are used (stored in the path object for that plane) to set the position and direction.
Warning the code for path does little to no vetting and thus can easily be made to throw an error. It is assumed that you write the path interface to the D3.js functionality you want.
const doFor = (count,callback) => {var i=0;while(i < count){callback(i++)}};
function createIcon(drawFunc){
const icon = document.createElement("canvas");
icon.width = icon.height = 10;
drawFunc(icon.getContext("2d"));
return icon;
}
function drawPlane(ctx){
const cx = ctx.canvas.width / 2;
const cy = ctx.canvas.height / 2;
ctx.beginPath();
ctx.strokeStyle = ctx.fillStyle = "red";
ctx.lineWidth = cx / 2;
ctx.lineJoin = "round";
ctx.lineCap = "round";
ctx.moveTo(cx/2,cy)
ctx.lineTo(cx * 1.5,cy);
ctx.moveTo(cx,cy/2)
ctx.lineTo(cx,cy*1.5)
ctx.stroke();
ctx.lineWidth = cx / 4;
ctx.moveTo(cx * 1.7,cy * 0.6)
ctx.lineTo(cx * 1.7,cy*1.4)
ctx.stroke();
}
const path = {
wayPoints : null, // holds way points
nextTarget : null, // holds next target waypoint
current : null, // hold previously passed way point
x : 0, // current pos x
y : 0, // current pos y
addWayPoint(x,y,time){
this.wayPoints.push({x,y,time});
},
start(){
if(this.wayPoints.length > 1){
this.current = this.wayPoints.shift();
this.nextTarget = this.wayPoints.shift();
}
},
getNextTarget(){
this.current = this.nextTarget;
if(this.wayPoints.length === 0){ // no more way points
return;
}
this.nextTarget = this.wayPoints.shift(); // get the next target
},
getPos(time){
while(this.nextTarget.time < time && this.wayPoints.length > 0){
this.getNextTarget(); // get targets untill the next target is ahead in time
}
if(this.nextTarget.time < time){
return true; // has arrivecd at target
}
// get time normalised ove time between current and next
var timeN = (time - this.current.time) / (this.nextTarget.time - this.current.time);
this.x = timeN * (this.nextTarget.x - this.current.x) + this.current.x;
this.y = timeN * (this.nextTarget.y - this.current.y) + this.current.y;
return false; // has not arrived
}
}
const planes = {
items : [],
icon : createIcon(drawPlane),
clear(){
planes.items.length = 0;
},
add(x,y){
var p;
planes.items.push(p = {
x,y,
ax : 0, // the direction of the x axis of this plane
ay : 0,
path : Object.assign({},path,{wayPoints : []}),
})
return p; // return the plane
},
update(time){
var i,p;
for(i = 0; i < planes.items.length; i ++){
p = planes.items[i];
if(p.path.getPos(time)){ // target reached
planes.items.splice(i--,1); // remove
}else{
p.dir = Math.atan2(p.y - p.path.y, p.x - p.path.x) + Math.PI; // add 180 because i drew plane wrong way around.
p.ax = Math.cos(p.dir);
p.ay = Math.sin(p.dir);
p.x = p.path.x;
p.y = p.path.y;
}
}
},
draw(){
var i,p;
const w = canvas.width;
const h = canvas.height;
for(i = 0; i < planes.items.length; i ++){
p = planes.items[i];
var x = ((p.x % w) + w) % w;
var y = ((p.y % h) + h) % h;
ctx.setTransform(-p.ax,-p.ay,p.ay,-p.ax,x,y);
ctx.drawImage(planes.icon,-planes.icon.width / 2,-planes.icon.height / 2);
}
}
}
const ctx = canvas.getContext("2d");
function mainLoop(time){
if(canvas.width !== innerWidth || canvas.height !== innerHeight){
canvas.width = innerWidth;
canvas.height = innerHeight;
planes.clear();
doFor(810,()=>{
var p = planes.add(Math.random() * canvas.width, Math.random() * canvas.height);
// now add random number of way points
var timeP = time;
// info to create a random path
var dir = Math.random() * Math.PI * 2;
var x = p.x;
var y = p.y;
doFor(Math.floor(Math.random() * 80 + 12),()=>{
var dist = Math.random() * 5 + 4;
x += Math.cos(dir) * dist;
y += Math.sin(dir) * dist;
dir += (Math.random()-0.5)*0.3;
timeP += Math.random() * 1000 + 500;
p.path.addWayPoint(x,y,timeP);
});
// last waypoin at center of canvas.
p.path.addWayPoint(canvas.width / 2,canvas.height / 2,timeP + 5000);
p.path.start();
})
}
ctx.setTransform(1,0,0,1,0,0);
// clear or render a background map
ctx.clearRect(0,0,canvas.width,canvas.height);
planes.update(time);
planes.draw();
requestAnimationFrame(mainLoop)
}
requestAnimationFrame(mainLoop)
canvas {
position : absolute;
top : 0px;
left : 0px;
}
<canvas id=canvas></canvas>
800 animated points
#Blindman67 is correct, clear and redraw everything, every frame.
I'm here just to say that when dealing with such primitive shapes as arc without too many color variations, it's actually better to use the arc method than drawImage().
The idea is to wrap all your shapes in a single path declaration, using
ctx.beginPath(); // start path declaration
for(i; i<shapes.length; i++){ // loop through our points
ctx.moveTo(pt.x + pt.radius, pt.y); // default is lineTo and we don't want it
// Note the '+ radius', arc starts at 3 o'clock
ctx.arc(pt.x, pt.y, pt.radius, 0, Math.PI*2);
}
ctx.fill(); // a single fill()
This is faster than drawImage, but the main caveat is that it works only for single-colored set of shapes.
I've made an complex plotting app, where I do draw a lot (20K+) of entities, with animated positions. So what I do, is to store two sets of points, one un-sorted (actually sorted by radius), and one
sorted by color. I then do use the sorted-by-color one in my animations loop, and when the animation is complete, I draw only the final frame with the sorted-by-radius (after I filtered the non visible entities). I achieve 60fps on most devices. When I tried with drawImage, I was stuck at about 10fps for 5K points.
Here is a modified version of Blindman67's good answer's snippet, using this single-path approach.
/* All credits to SO user Blindman67 */
const doFor = (count,callback) => {var i=0;while(i < count){callback(i++)}};
const planes = {
items : [],
clear(){
planes.items.length = 0;
},
add(x,y){
planes.items.push({
x,y,
rad: 2,
dir : Math.random() * Math.PI * 2,
speed : Math.random() * 0.2 + 0.1,
dirV : (Math.random() - 0.5) * 0.01, // change in direction
})
},
update(){
var i,p;
for(i = 0; i < planes.items.length; i ++){
p = planes.items[i];
p.dir += p.dirV;
p.x += Math.cos(p.dir) * p.speed;
p.y += Math.sin(p.dir) * p.speed;
}
},
draw(){
var i,p;
const w = canvas.width;
const h = canvas.height;
ctx.beginPath();
ctx.fillStyle = 'red';
for(i = 0; i < planes.items.length; i ++){
p = planes.items[i];
var x = ((p.x % w) + w) % w;
var y = ((p.y % h) + h) % h;
ctx.moveTo(x + p.rad, y)
ctx.arc(x, y, p.rad, 0, Math.PI*2);
}
ctx.fill();
}
}
const ctx = canvas.getContext("2d");
function mainLoop(){
if(canvas.width !== innerWidth || canvas.height !== innerHeight){
canvas.width = innerWidth;
canvas.height = innerHeight;
planes.clear();
doFor(8000,()=>{ planes.add(Math.random() * canvas.width, Math.random() * canvas.height) })
}
ctx.setTransform(1,0,0,1,0,0);
// clear or render a background map
ctx.clearRect(0,0,canvas.width,canvas.height);
planes.update();
planes.draw();
requestAnimationFrame(mainLoop)
}
requestAnimationFrame(mainLoop)
canvas {
position : absolute;
top : 0px;
left : 0px;
z-index: -1;
}
<canvas id=canvas></canvas>
8000 animated points
Not directly related but in case you've got part of your drawings that don't update at the same rate as the rest (e.g if you want to highlight an area of your map...) then you might also consider separating your drawings in different layers, on offscreen canvases. This way you'd have one canvas for the planes, that you'd clear every frame, and other canvas for other layers that you would update at different rate. But that's an other story.
I have a set of javascript code which creates a circle object and then pushes it onto the canvas. Is there a way so that if a user were to click on one of the circles the object would disappear?
Here's my Javascript Code
// get a reference to the canvas and its context
var canvas = document.getElementById("canvas");
var ctx = canvas.getContext("2d");
// set canvas to equal window size
window.addEventListener('resize', resizeCanvas, false);
// newly spawned objects start at Y=25
var spawnLineY = 25;
// spawn a new object every 1500ms
var spawnRate = 1500;
// when was the last object spawned
var lastSpawn = -1;
// this array holds all spawned object
var objects = [];
// save the starting time (used to calc elapsed time)
var startTime = Date.now();
// start animating
animate();
function resizeCanvas() {
canvas.width = window.innerWidth;
canvas.height = window.innerHeight;
/**
* Your drawings need to be inside this function otherwise they will
be reset when
* you resize the browser window and the canvas goes will be cleared.
*/
}
function spawnRandomObject() {
// select a random type for this new object
var t;
// About Math.random()
// Math.random() generates a semi-random number
// between 0-1. So to randomly decide if the next object
// will be A or B, we say if the random# is 0-.49 we
// create A and if the random# is .50-1.00 we create B
var random;
random = Math.random();
if (random < 0.75 && random > .50) {
t = "red";
} else if (random > .75) {
t = "blue";
} else if (random < .50 && random > .25) {
t = "purple"
} else if (random < .25) {
t = "green"
}
// create the new object
var object = {
// set this objects type
type: t,
// set x randomly but at least 15px off the canvas edges
x: Math.random() * (canvas.width - 30) + 15,
// set y to start on the line where objects are spawned
y: spawnLineY,
downspeed: Math.floor((Math.random() * 100) + 5)/100,
radius: Math.floor((Math.random() * 175) + 5),
onclick : alert('blah'),
}
// add the new object to the objects[] array
objects.push(object);
}
// the code to make the circle disappear would go here
popBalloon()
function animate() {
// get the elapsed time
var time = Date.now();
// see if its time to spawn a new object
if (time > (lastSpawn + spawnRate)) {
lastSpawn = time;
spawnRandomObject();
}
// request another animation frame
requestAnimationFrame(animate);
// clear the canvas so all objects can be
// redrawn in new positions
ctx.clearRect(0, 0, canvas.width, canvas.height);
// draw the line where new objects are spawned
ctx.beginPath();
ctx.moveTo(0, spawnLineY);
ctx.lineTo(canvas.width, spawnLineY);
ctx.stroke();
// move each object down the canvas
for (var i = 0; i < objects.length; i++) {
var object = objects[i];
object.y += object.downspeed;
ctx.beginPath();
ctx.arc(object.x, object.y, object.radius, 0, Math.PI * 2);
ctx.closePath();
ctx.fillStyle = object.type;
ctx.fill();
}
}
resizeCanvas();
To get the mouse click position on the canvas
// assuming canvas is already defined and references an DOM canvas Element
const mouse = {x ;0,y :0, clicked : false};
function mouseClickEvent(event){
mouse.x = event.offsetX;
mouse.y = event.offsetY;
mouse.clicked = true;
}
canvas.addEventListener("click",mouseClickEvent);
Then in your render loop check for mouse clicks
if(mouse.clicked){
// do what is needed
mouse.clicked = false; /// clear the clicked flag
}
To find out if a point is inside a circle
// points is {x,y}
// circle is {x,y,r} where r is radius
// returns true if point touches circle
function isPointInCircle(point,circle){
var x = point.x - circle.x;
var y = point.y - circle.y;
return Math.sqrt(x * x + y * y) <= circle.r;
}
Or with ES6
function isPointInCircle(point,circle){
return Math.hypot(point.x - circle.x, point.y - circle.y) <= circle.r;
}
I am not entirely sure how to get the mouse x and y position but if you can get that this function should help detect collision
function checkColision()// if mouse collides with object
{
for (var i = 0; i < objects.length; i++)
{
// get the distance between mouse and object
var xRange = Math.abs(mouse.x - object[i].x);//abslute value so no negative numbers
var yRange = Math.abs(mouse.y - object[i].y);
if (xRange < MIN_COLISION_RANGE && yRange < MIN_COLISION_RANGE)
{
object.splice(i, 1);//remove object
i--;//go back one iteration
}
}
}
My question is, what is the best way to tint an image that is drawn using the drawImage method. The target useage for this is advanced 2d particle-effects (game development) where particles change colors over time etc. I am not asking how to tint the whole canvas, only the current image i am about to draw.
I have concluded that the globalAlpha parameter affects the current image that is drawn.
//works with drawImage()
canvas2d.globalAlpha = 0.5;
But how do i tint each image with an arbitrary color value ? It would be awesome if there was some kind of globalFillStyle or globalColor or that kind of thing...
EDIT:
Here is a screenshot of the application i am working with:
http://twitpic.com/1j2aeg/full
alt text http://web20.twitpic.com/img/92485672-1d59e2f85d099210d4dafb5211bf770f.4bd804ef-scaled.png
You have compositing operations, and one of them is destination-atop. If you composite an image onto a solid color with the 'context.globalCompositeOperation = "destination-atop"', it will have the alpha of the foreground image, and the color of the background image. I used this to make a fully tinted copy of an image, and then drew that fully tinted copy on top of the original at an opacity equal to the amount that I want to tint.
Here is the full code:
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd">
<html>
<head>
<title>HTML5 Canvas Test</title>
<script type="text/javascript">
var x; //drawing context
var width;
var height;
var fg;
var buffer
window.onload = function() {
var drawingCanvas = document.getElementById('myDrawing');
// Check the element is in the DOM and the browser supports canvas
if(drawingCanvas && drawingCanvas.getContext) {
// Initaliase a 2-dimensional drawing context
x = drawingCanvas.getContext('2d');
width = x.canvas.width;
height = x.canvas.height;
// grey box grid for transparency testing
x.fillStyle = '#666666';
x.fillRect(0,0,width,height);
x.fillStyle = '#AAAAAA';
var i,j;
for (i=0; i<100; i++){
for (j=0; j<100; j++){
if ((i+j)%2==0){
x.fillRect(20*i,20*j,20,20);
}
}
}
fg = new Image();
fg.src = 'http://uncc.ath.cx/LayerCake/images/16/3.png';
// create offscreen buffer,
buffer = document.createElement('canvas');
buffer.width = fg.width;
buffer.height = fg.height;
bx = buffer.getContext('2d');
// fill offscreen buffer with the tint color
bx.fillStyle = '#FF0000'
bx.fillRect(0,0,buffer.width,buffer.height);
// destination atop makes a result with an alpha channel identical to fg, but with all pixels retaining their original color *as far as I can tell*
bx.globalCompositeOperation = "destination-atop";
bx.drawImage(fg,0,0);
// to tint the image, draw it first
x.drawImage(fg,0,0);
//then set the global alpha to the amound that you want to tint it, and draw the buffer directly on top of it.
x.globalAlpha = 0.5;
x.drawImage(buffer,0,0);
}
}
</script>
</head>
</body>
<canvas id="myDrawing" width="770" height="400">
<p>Your browser doesn't support canvas.</p>
</canvas>
</body>
</html>
There is a method here you can use to tint images, and it's more accurate then drawing coloured rectangles and faster then working on a pixel-by-pixel basis. A full explanation is in that blog post, including the JS code, but here is a summary of how it works.
First you go through the image you are tinting pixel by pixel, reading out the data and splitting each pixel up into 4 separate components: red, green, blue and black. You write each component to a separate canvas. So now you have 4 (red, green, blue and black) versions of the original image.
When you want to draw a tinted image, you create (or find) an off-screen canvas and draw these components to it. The black is drawn first, and then you need set the globalCompositeOperation of the canvas to 'lighter' so the next components are added to the canvas. The black is also non-transparent.
The next three components are drawn (the red, blue and green images), but their alpha value is based on how much their component makes up the drawing colour. So if the colour is white, then all three are drawn with 1 alpha. If the colour is green, then only the green image is drawn and the other two are skipped. If the colour is orange then you have full alpha on the red, draw green partially transparent and skip the blue.
Now you have a tinted version of your image rendered onto the spare canvas, and you just draw it to where ever you need it on your canvas.
Again the code to do this is in the blog post.
Unfortunately, there is not simply one value to change similar to openGL or DirectX libraries I've used in the past. However, it's not too much work to create a new buffer canvas and use the available globalCompositeOperation when drawing an image.
// Create a buffer element to draw based on the Image img
const buffer = document.createElement('canvas');
buffer.width = img.width;
buffer.height = img.height;
const btx = buffer.getContext('2d');
// First draw your image to the buffer
btx.drawImage(img, 0, 0);
// Now we'll multiply a rectangle of your chosen color
btx.fillStyle = '#FF7700';
btx.globalCompositeOperation = 'multiply';
btx.fillRect(0, 0, buffer.width, buffer.height);
// Finally, fix masking issues you'll probably incur and optional globalAlpha
btx.globalAlpha = 0.5;
btx.globalCompositeOperation = 'destination-in';
btx.drawImage(img, 0, 0);
You can now use buffer as your first parameter canvas2d.drawImage. Using multiply you'll get literal tint but hue and color may also be to your liking. Also, this is fast enough to wrap in a function for reuse.
When I created a particle test I just cached images based on rotation (like 35 rotations), color tint, and alpha and created a wrapper so that they were created automatically. Worked well. Yes there should be some kind of tint operation, but when dealing with software rendering your best bet much like in flash is to cache everything.
Particle Example I made for fun
<!DOCTYPE HTML>
<html lang="en">
<head>
<title>Particle Test</title>
<script language="javascript" src="../Vector.js"></script>
<script type="text/javascript">
function Particle(x, y)
{
this.position = new Vector(x, y);
this.velocity = new Vector(0.0, 0.0);
this.force = new Vector(0.0, 0.0);
this.mass = 1;
this.alpha = 0;
}
// Canvas
var canvas = null;
var context2D = null;
// Blue Particle Texture
var blueParticleTexture = new Image();
var blueParticleTextureLoaded = false;
var blueParticleTextureAlpha = new Array();
var mousePosition = new Vector();
var mouseDownPosition = new Vector();
// Particles
var particles = new Array();
var center = new Vector(250, 250);
var imageData;
function Initialize()
{
canvas = document.getElementById('canvas');
context2D = canvas.getContext('2d');
for (var createEntity = 0; createEntity < 150; ++createEntity)
{
var randomAngle = Math.random() * Math.PI * 2;
var particle = new Particle(Math.cos(randomAngle) * 250 + 250, Math.sin(randomAngle) * 250 + 250);
particle.velocity = center.Subtract(particle.position).Normal().Normalize().Multiply(Math.random() * 5 + 2);
particle.mass = Math.random() * 3 + 0.5;
particles.push(particle);
}
blueParticleTexture.onload = function()
{
context2D.drawImage(blueParticleTexture, 0, 0);
imageData = context2D.getImageData(0, 0, 5, 5);
var imageDataPixels = imageData.data;
for (var i = 0; i <= 255; ++i)
{
var newImageData = context2D.createImageData(5, 5);
var pixels = newImageData.data;
for (var j = 0, n = pixels.length; j < n; j += 4)
{
pixels[j] = imageDataPixels[j];
pixels[j + 1] = imageDataPixels[j + 1];
pixels[j + 2] = imageDataPixels[j + 2];
pixels[j + 3] = Math.floor(imageDataPixels[j + 3] * i / 255);
}
blueParticleTextureAlpha.push(newImageData);
}
blueParticleTextureLoaded = true;
}
blueParticleTexture.src = 'blueparticle.png';
setInterval(Update, 50);
}
function Update()
{
// Clear the screen
context2D.clearRect(0, 0, canvas.width, canvas.height);
for (var i = 0; i < particles.length; ++i)
{
var particle = particles[i];
var v = center.Subtract(particle.position).Normalize().Multiply(0.5);
particle.force = v;
particle.velocity.ThisAdd(particle.force.Divide(particle.mass));
particle.velocity.ThisMultiply(0.98);
particle.position.ThisAdd(particle.velocity);
particle.force = new Vector();
//if (particle.alpha + 5 < 255) particle.alpha += 5;
if (particle.position.Subtract(center).LengthSquared() < 20 * 20)
{
var randomAngle = Math.random() * Math.PI * 2;
particle.position = new Vector(Math.cos(randomAngle) * 250 + 250, Math.sin(randomAngle) * 250 + 250);
particle.velocity = center.Subtract(particle.position).Normal().Normalize().Multiply(Math.random() * 5 + 2);
//particle.alpha = 0;
}
}
if (blueParticleTextureLoaded)
{
for (var i = 0; i < particles.length; ++i)
{
var particle = particles[i];
var intensity = Math.min(1, Math.max(0, 1 - Math.abs(particle.position.Subtract(center).Length() - 125) / 125));
context2D.putImageData(blueParticleTextureAlpha[Math.floor(intensity * 255)], particle.position.X - 2.5, particle.position.Y - 2.5, 0, 0, blueParticleTexture.width, blueParticleTexture.height);
//context2D.drawImage(blueParticleTexture, particle.position.X - 2.5, particle.position.Y - 2.5);
}
}
}
</script>
<body onload="Initialize()" style="background-color:black">
<canvas id="canvas" width="500" height="500" style="border:2px solid gray;"/>
<h1>Canvas is not supported in this browser.</h1>
</canvas>
<p>No directions</p>
</body>
</html>
where vector.js is just a naive vector object:
// Vector class
// TODO: EXamples
// v0 = v1 * 100 + v3 * 200;
// v0 = v1.MultiplY(100).Add(v2.MultiplY(200));
// TODO: In the future maYbe implement:
// VectorEval("%1 = %2 * %3 + %4 * %5", v0, v1, 100, v2, 200);
function Vector(X, Y)
{
/*
this.__defineGetter__("X", function() { return this.X; });
this.__defineSetter__("X", function(value) { this.X = value });
this.__defineGetter__("Y", function() { return this.Y; });
this.__defineSetter__("Y", function(value) { this.Y = value });
*/
this.Add = function(v)
{
return new Vector(this.X + v.X, this.Y + v.Y);
}
this.Subtract = function(v)
{
return new Vector(this.X - v.X, this.Y - v.Y);
}
this.Multiply = function(s)
{
return new Vector(this.X * s, this.Y * s);
}
this.Divide = function(s)
{
return new Vector(this.X / s, this.Y / s);
}
this.ThisAdd = function(v)
{
this.X += v.X;
this.Y += v.Y;
return this;
}
this.ThisSubtract = function(v)
{
this.X -= v.X;
this.Y -= v.Y;
return this;
}
this.ThisMultiply = function(s)
{
this.X *= s;
this.Y *= s;
return this;
}
this.ThisDivide = function(s)
{
this.X /= s;
this.Y /= s;
return this;
}
this.Length = function()
{
return Math.sqrt(this.X * this.X + this.Y * this.Y);
}
this.LengthSquared = function()
{
return this.X * this.X + this.Y * this.Y;
}
this.Normal = function()
{
return new Vector(-this.Y, this.X);
}
this.ThisNormal = function()
{
var X = this.X;
this.X = -this.Y
this.Y = X;
return this;
}
this.Normalize = function()
{
var length = this.Length();
if(length != 0)
{
return new Vector(this.X / length, this.Y / length);
}
}
this.ThisNormalize = function()
{
var length = this.Length();
if (length != 0)
{
this.X /= length;
this.Y /= length;
}
return this;
}
this.Negate = function()
{
return new Vector(-this.X, -this.Y);
}
this.ThisNegate = function()
{
this.X = -this.X;
this.Y = -this.Y;
return this;
}
this.Compare = function(v)
{
return Math.abs(this.X - v.X) < 0.0001 && Math.abs(this.Y - v.Y) < 0.0001;
}
this.Dot = function(v)
{
return this.X * v.X + this.Y * v.Y;
}
this.Cross = function(v)
{
return this.X * v.Y - this.Y * v.X;
}
this.Projection = function(v)
{
return this.MultiplY(v, (this.X * v.X + this.Y * v.Y) / (v.X * v.X + v.Y * v.Y));
}
this.ThisProjection = function(v)
{
var temp = (this.X * v.X + this.Y * v.Y) / (v.X * v.X + v.Y * v.Y);
this.X = v.X * temp;
this.Y = v.Y * temp;
return this;
}
// If X and Y aren't supplied, default them to zero
if (X == undefined) this.X = 0; else this.X = X;
if (Y == undefined) this.Y = 0; else this.Y = Y;
}
/*
Object.definePropertY(Vector, "X", {get : function(){ return X; },
set : function(value){ X = value; },
enumerable : true,
configurable : true});
Object.definePropertY(Vector, "Y", {get : function(){ return X; },
set : function(value){ X = value; },
enumerable : true,
configurable : true});
*/
This question still stands. The solution some seem to be suggesting is drawing the image to be tinted onto another canvas and from there grabbing the ImageData object to be able to modify it pixel by pixel, the problem with this is that it is not really acceptable in a game development context because i basically will have to draw each particle 2 times instead of 1. A solution i am about to try is to draw each particle once on a canvas and grabbing the ImageData object, before the actual application starts, and then work with the ImageData object instead of the actual Image object but it might prove kind of costly to create new copies since i will have to keep an unmodified original ImageData object for each graphic.
I would take a look at this: http://www.arahaya.com/canvasscript3/examples/ he seems to have a ColorTransform method, I believe he is drawing a shape to do the transform but perhaps based on this you can find a way to adjust a specific image.