I am trying to create a small game to learn javascript.Everything works fine except my Rect class.As a matter of fact key_click works fine when it executes some console.log, but doesn’t display anything with tile.draw_tile() (nor gives any error).Could you help me?
var canvas = document.querySelector('canvas');
var c = canvas.getContext('2d');
canvas.width = window.innerWidth;
canvas.height = window.innerHeight;
let Rect = class {
constructor(x, y, width, height) {
this.x = x;
this.y = y;
this.width = width;
this.height = height;
}
draw_tile() {
c.fillStyle = "red";
c.fillRect(this.x, this.y, this.width, this.height);
}
}
var mouse = {
x: undefined,
y: undefined,
key_move: window.addEventListener('mousemove',(event)=>{
mouse.x = event.clientX;
mouse.y= event.clientY;
}),
key_click:window.addEventListener('click',(event)=>{
tile.draw_tile();
})
}
let tile = new Rect(mouse.x, mouse.y, 30, 30);
main = function(){
mouse.key_move;
mouse.key_click;
window.requestAnimationFrame(main);
}
window.requestAnimationFrame(main);
Related
I want to draw many different sized circles with the same image on them using a prototype. The problem is, the circles don't appear with the images drawn on them.
The circles are still there because they're visible when stroke is used, but the images aren't drawn. I was able to have an arc be drawn with an image in it without the prototype but as soon as I use it, it doesn't work.
No bugs appear in the console, so it is not clear to me what I'm missing.
I've tried moving the event listener outside the prototype but the circle images still did not appear.
If anyone has any insight and perhaps a solution as to why this isn't working that they can share, that would be very much appreciated.
Here is the code:
const ctx = document.getElementById('canvas').getContext('2d');
class Balls {
constructor(xPos, yPos, radius){
this.xPos = xPos;
this.yPos = yPos;
this.radius = radius;
}
}
Balls.prototype.render = function(){
const img = document.createElement('img');
img.src = 'crystal.jpg';
ctx.arc(this.xPos, this.yPos, this.radius, 0, Math.PI*2)
ctx.stroke();
ctx.clip();
img.addEventListener('onload', function(e){
ctx.drawImage(img, this.xPos - this.radius, this.yPos - this.radius,
this.radius*2, this.radius*2);
});
};
let object = new Balls(100, 100, 50);
object.render();
<canvas id='canvas'></canvas>
Here you go, i just changed 2 things here in order to make your code work.
load is used for eventlistener instead on onload.
use Arrow function in order to rely on the parent context instead of dynamic context(this).
const ctx = document.getElementById('canvas').getContext('2d');
class Balls {
constructor(xPos, yPos, radius) {
this.xPos = xPos;
this.yPos = yPos;
this.radius = radius;
}
}
Balls.prototype.render = function() {
const img = document.createElement('img');
img.src = 'https://via.placeholder.com/150.png?text=vijay'
ctx.arc(this.xPos, this.yPos, this.radius, 0, Math.PI * 2)
ctx.stroke();
ctx.clip();
img.addEventListener('load', (e) => {
ctx.drawImage(img, this.xPos - this.radius, this.yPos - this.radius,
this.radius * 2, this.radius * 2);
});
};
let object = new Balls(100, 100, 50);
object.render();
<canvas id='canvas'></canvas>
You had two issues in your code. Firstly, the onload event should be load. Secondly, this is not known inside the event listener function, so this.radius etc. are all undefined and ctx.drawImage(img, this.xPos - this.radius, this.yPos - this.radius,
this.radius*2, this.radius*2) doesn't work.
I used some variables for this.xPos, this.yPos, this.radius that can be used inside the event listener callback function.
Hope this helps!
const ctx = document.getElementById('canvas').getContext('2d');
class Balls {
constructor(xPos, yPos, radius) {
this.xPos = xPos;
this.yPos = yPos;
this.radius = radius;
}
}
Balls.prototype.render = function() {
const img = new Image();
img.src = 'https://source.unsplash.com/random';
var xPos = this.xPos, yPos = this.yPos, radius = this.radius
ctx.arc(xPos, yPos, radius, 0, Math.PI * 2)
ctx.stroke();
ctx.clip();
img.addEventListener('load', function(e) {
console.log("load")
ctx.drawImage(img, xPos - radius, yPos - radius,
radius*2, radius*2);
});
};
let object = new Balls(100, 100, 50);
object.render();
<canvas id='canvas'></canvas>
This is an alternative way you can load images which is more modular, If you are making a game an Img class will come in handy.
Off-topic -
if you want to load multiple images then you can add atotalLoadedcounter to keep track of how many images has been loaded and if thetotalLoadedcount is equal tototalImagescount then you can call a callback which will fire the animationLoop and preloads all the images.
const ctx = document.getElementById('canvas').getContext('2d');
// Img class to provide modular code
class Img {
constructor(src, x, y, size) {
this.x = x;
this.y = y;
this.size = size;
this.src = src;
this.img = new Image();
this.img.src = this.src;
this.isLoaded = false;
this.img.addEventListener('load', (e) => {
this.isLoaded = true;
this.draw();
});
}
draw() {
if (this.isLoaded) {
ctx.drawImage(this.img, this.x, this.y, this.size, this.size);
}
}
}
class Balls {
constructor(xPos, yPos, radius) {
this.xPos = xPos;
this.yPos = yPos;
this.radius = radius;
}
}
Balls.prototype.render = function() {
let imgx = this.xPos - this.radius;
let imgy = this.yPos - this.radius;
let imgr = this.radius * 2;
let url = 'https://via.placeholder.com/150.png?text=Better';
const img = new Img(url, imgx, imgy, imgr);
ctx.arc(this.xPos, this.yPos, this.radius, 0, Math.PI * 2)
ctx.stroke();
ctx.clip();
img.draw();
};
let object = new Balls(100, 100, 50);
object.render();
<canvas id='canvas'></canvas>
Im trying to create and delete arcs on events, to adding parts works fine and i'm saving them in arrays so i could delete them on calling an event listener by somehow that's not happening , I mean its working fine in the console as in the array values are decremented by its not updating in the canvas
Code:
<script>
var myCanvas = document.getElementById("myCanvas");
myCanvas.width = window.innerWidth;
myCanvas.height = 500;
var c = myCanvas.getContext("2d");
var myArr = [];
myCanvas.addEventListener("click", function(){
var x = event.x;
var y = event.y;
var radius = 10;
myArr.push(new CreateCircle(x, y, radius, "#34495e"));
console.log( myArr );
});
window.addEventListener('keydown', function(){
myArr.splice(0,1);
console.log(myArr);
});
function CreateCircle(x, y, radius, color) {
this.x = x;
this.y = y;
this.radius = radius;
this.color = color;
this.draw = function() {
c.beginPath();
c.arc(this.x, this.y, this.radius, 0, Math.PI*2);
c.fillStyle = this.color;
c.fill();
}
this.draw();
}
</script>
Do i need to add an delete function in the constructor function and call it on keydown event , how do i go on doing it/fixing it ?
To remove the circles, you have to clear the canvas, and then redraw it with the modified array of circles.
First of all, return an object from the CreateCircle method, so you have something to work with. There's no need for instances here.
Secondly, you could clear the canvas by resetting it's width, and then redraw based on the array, like this
var myCanvas = document.getElementById("myCanvas");
myCanvas.width = window.innerWidth;
myCanvas.height = 500;
var c = myCanvas.getContext("2d");
var myArr = [];
myCanvas.addEventListener("click", function() {
var x = event.x;
var y = event.y;
var radius = 10;
myArr.push(CreateCircle(x, y, radius, "#34495e"));
});
window.addEventListener('keydown', function() {
myArr.splice(0, 1);
myCanvas.width = myCanvas.width;
myArr.forEach(function(circle) {
CreateCircle(circle.x, circle.y, circle.r, circle.c)
})
});
function CreateCircle(x, y, radius, color) {
c.beginPath();
c.arc(x, y, radius, 0, Math.PI * 2);
c.fillStyle = color;
c.fill();
return {x: x, y: y, r: radius, c: color};
}
<canvas id="myCanvas"></canvas>
You don't update canvas anywhere. You need to create some sort of "render" function which will clear previously rendered frame and then loops through circles in array and call .draw on all of them.
Tip:
context.clearRect method is useful for clearing canvas.
I already create my canvas on my page, however when I try to import an image on the canvas, it does not appear, here are the code I used. (the makeGameArea is a method I created to make a canvas on the webpage, the code of this method is not shown because it is so long to put it here)
Here are the following code that should have problem
var myGameArea2 = makeGameArea(700, 150, "myArea", "white");
var myContext2 = myGameArea2.getContext("2d");
var myImage = new drawImage(myContext2, "sonic.gif", 91, 97, 0, 0);
myImage.draw();
function drawImage(ctx, src, width, height, x, y){
this.image = new Image();
this.image.src = src;
this.width = width;
this.height = height;
this.x = x;
this.y = y;
this.draw = function(){
this.image.onload = function(){
ctx.drawImage(this.image, this.x, this.y, this.width, this.height);
}
}
}
Is there anything wrong with my drawImage() method?
HTMLImage.onload will fire only once per src setting.
Here you are attaching your handler in the draw method, which I guess will be called later on. At this moment, the event will already have fired, and hence will never be called, since it won't fire again unless you reset its src.
Fixed code block:
function drawImage(ctx, src, width, height, x, y){
this.image = new Image();
this.width = width;
this.height = height;
this.x = x;
this.y = y;
this.draw = function(){
ctx.drawImage(this.image, this.x, this.y, this.width, this.height));
};
// if you want it to draw as soon as possible
this.image.onload = this.draw.bind(this);
this.image.src = src;
}
I have no idea what is wrong. This is being made on a completely new site, so there are no cache problems, and the javascript console isn't returning errors. The canvas spans over the whole page, and is tagged properly. Here is the script:
<script type = "text/javascript">
var game = document.getElementById("game");
var context = game.getContext("2d");
var gamePieces = []
function gamePiece(width, height, color, x, y){
this.width = width;
this.height = height;
this.x = x;
this.y = y;
update = function(){
context.fillStyle = color;
context.fillRect(this.x, this.y, this.height, this.width);
}
gamePieces[gamePieces.length] = this
}
var p1 = gamePiece(50, 50, "blue", 0, 0);
function update(){
context.clearRect(0, 0, game.width, game.height);
for(var i = 0; i < gamePieces.length; i++){
gamePieces[i].update();
}
}
</script>
Nevermind. I figured it out.
Everything is running smoothly, I just needed to add another context.fillstyle and context.fillRect() statement. derpyderp.
This script is endlessly taking memory in all the browsers. I can't see why!
var canvas = document.getElementById("canvas");
var ctx = canvas.getContext("2d");
var particles = [], amount = 5;
var x = 100; var y = 100;
var W, H;
var p, gradient;
//dimensions
if(window.innerHeight){
W = window.innerWidth, H = window.innerHeight;
}else{
W = document.documentElement.clientWidth, H = document.documentElement.clientHeight;
}
canvas.width = W, canvas.height = H;
//array voor de meerdere particles
for(var i=0;i<amount;i++){
particles.push(new create_particle());
}
function create_particle(){
//random positie op canvas
this.x = Math.random()*W;
this.y = Math.random()*H;
//random snelheid
this.vx = Math.random()*20-10;
this.vy = Math.random()*20-10;
//Random kleur
var r = Math.random()*255>>0;
var g = Math.random()*255>>0;
var b = Math.random()*255>>0;
this.color = "rgba("+r+", "+g+", "+b+", 0.5)";
this.radius = Math.random()*20+20;
}
window.requestAnimFrame = (function(){
return window.requestAnimationFrame ||
window.webkitRequestAnimationFrame ||
window.mozRequestAnimationFrame ||
window.oRequestAnimationFrame ||
window.msRequestAnimationFrame ||
function( callback ){
window.setTimeout(callback, 1000 / 60);
};
})();
function draw(){
canvas.width = canvas.width;
canvas.height = canvas.height;
//achtergrond tekenen
//ctx.globalCompositeOperation = "source-over";
//ctx.fillStyle = "rgba(0,0,0,0.5)";
ctx.fillRect(0, 0, W, H);
//ctx.globalCompositeOperation = "lighter";
//teken cirkel
for(var t=0; t<particles.length;t++){
p = particles[t];
//gradient
gradient = ctx.createRadialGradient(p.x,p.y,0,p.x,p.y,p.radius);
gradient.addColorStop(0,"white");
gradient.addColorStop(0.4,"white");
gradient.addColorStop(0.4,p.color);
gradient.addColorStop(1,"black");
ctx.beginPath();
ctx.fillStyle = gradient;
ctx.arc(p.x,p.y,p.radius,Math.PI*2,false)
ctx.fill();
//beweeg
p.x+=p.vx;
p.y+=p.vy;
//canvas boundery detect
if(p.x < -50)p.x = W+50;
if(p.y < -50)p.y=H+50;
if(p.x > W+50)p.x = -50;
if(p.y > H+50)p.y = -50;
}
}
(function animloop(){
canvas.width = canvas.width;
canvas.height = canvas.height;
requestAnimFrame(animloop);
draw();
})();
//resize?
function resizeCanvas(){
canvas.height = W;
canvas.width = H;
ctx.fillRect(0, 0, W, H);
}
if(window.addEventListener){
window.addEventListener('resize', resizeCanvas, false);
}else{
window.attachEvent('resize', resizeCanvas);
}
I tried to change some code around (this is also final version) but still it leaks. If you use this script and watch 'taskmanager' or in-browser's memory check you see that it slowly and constantly eats memory.
EDIT: after adding in the canvas.height solution and moving some declaring's around, the script still leaks! I must say that it looks like Firefox leaks harder then Chrome!
You have:
canvas.width = canvas.width;
canvas.height = canvas.height;
I'm guessing this does the same as clearRect... but to be sure try this too:
function draw(){
ctx.clearRect ( 0 , 0 , canvas.width , canvas.height );
/* draw */
}
See if any thing changes.
Try cleaning the canvas before starting another set of drawing. You can clear it by setting it's width and height again.
Here is some orientative code:
function draw() {
canvas.width = canvas.width;
canvas.height = canvas.height;
/* draw */
}
my guess is your create_particle function could be leaking but im not sure as how, one idea would be to create an interal object instead of using this
function create_particle(){
return {
x: Math.random()*W,
y: Math.random()*H,
vx: Math.random()*20-10,
vy: Math.random()*20-10,
r: Math.random()*255>>0,
g: Math.random()*255>>0,
b: Math.random()*255>>0,
color: "rgba("+r+", "+g+", "+b+", 0.5)",
radius: Math.random()*20+20,
};
}
Im not sure if this is the issue, but it seems to be the only thing I can really think of that kinda looks odd,