I am using node.js + socket.io to try and make a multiplier HTML5 canvas game. Unfortunately every time I go to draw all of the players, all the images end up on top of each other.
socket.on('drawPlayers', function(players){
context.clearRect ( 0 , 0 , gameWidth , gameHeight ); //clear canvas
for(var i=0; i<players.length; i++){
var cur = players[i];
var playerSprite = new Image();
playerSprite.onload = function() {
return context.drawImage(playerSprite, cur.x, cur.y);
};
playerSprite.src = 'images/sprite.png';
console.log("drawing player "+cur.un+" at ("+cur.x+","+cur.y+")");
}
});
The console.log() will log the different x and y values correctly, but all of the images end up on top of each other.
function player(id,username){
this.id = id;
this.un = username;
this.y = Math.floor(Math.random() * 501);
this.x = Math.floor(Math.random() * 801);
this.src = 'images/mobile_md_logo.png';
}
I
Jonathan Lonowski is right. For each of the onload triggers, cur points to the same player, the last one. There is only one cur that exists inside drawPlayers event handler.
Use this to separate the scope of cur from one that is in the loop:
function draw(sprite,cur){
return function() {
context.drawImage(sprite, cur.x, cur.y);
};
}
Then call it from inside the loop
for(var i=0; i<players.length; i++){
var cur = players[i];
var playerSprite = new Image();
playerSprite.onload = draw(playerSprite,cur);
playerSprite.src = 'images/sprite.png';
console.log("drawing player "+cur.un+" at ("+cur.x+","+cur.y+")");
}
Related
I have recently been working on a web based project using canvas on HTML5. The program consists of a 16x16 grid of tiles that have been pseudo-randomly generated. I am relatively new to canvas, but have built this program in several other environments, none of which however compile successfully to a web based language. this is the main code section that is giving me bother:
var A = 8765432352450986;
var B = 8765432352450986;
var M = 2576436549074795;
var X = 1;
var rx = 0;
var ry = 0;
this.image = new Image();
var i = 0;
var ii = 0;
while(i < 16)
{
while(ii < 16)
{
this.image = new Image();
this.image.src = "textures/grass.png";
x = (((A*X)+B)%M)%M;
if((x/2)%1 == 0)
{
this.image.src = "textures/grass.png";
}
if((x/8)%1 == 0)
{
this.image.src = "textures/hill.png";
}
if((x/21)%1 == 0)
{
this.image.src = "textures/trees.png";
}
if((x/24)%1 == 0)
{
this.image.src = "textures/sea.png";
}
if((x/55)%1 == 0)
{
this.image.src = "textures/mountain.png";
}
if((x/78)%1 == 0)
{
this.image.src = "textures/lake.png";
}
if((x/521)%1 == 0)
{
this.image.src = "textures/volcano.png";
}
if((x/1700)%1 == 0)
{
this.image.src = "textures/shrine.png";
}
if((x/1890)%1 == 0)
{
this.image.src = "textures/outpost.png";
}
if((x/1999)%1 == 0)
{
this.image.src = "textures/civ.png";
}
ctx = myGameArea.context;
ctx.drawImage(this.image,rx, ry, 20, 20);
ii ++;
rx += 20;
}
i ++;
rx = 0;
ry += 16;
}
I would like canvas to draw along the lines of this code above, effectively generating a grid like this
pre generated grid image
(please try and ignore the obvious bad tile drawings, I planned on either finding an artist or trying slightly harder on them when I get the game fully working.)
The black square is a separate movable object. I haven't got as far as implementing it in this version, but if you have any suggestions for it please tell me
in the full html file I have now, the canvas renders but none of the background (using the w3schools tutorials, I can make objects render however)
In short: how do I render a background consisting of a 16x16 grid of pseudo-random tiles on an event triggered or on page loaded, using canvas or if that does not work another web based technology
Thank you for your time.
A few problems but the main one is that you need to give an image some time to load before you can draw it to the canvas.
var image = new Image();
image.src = "image.png";
// at this line the image may or may not have loaded.
// If not loaded you can not draw it
To ensure an image has loaded you can add a onload event handler to the image
var image = new Image();
image.src = "image.png";
image.onload = function(){ ctx.drawImage(image,0,0); }
The onload function will be called after all the current code has run.
To load many images you want to know when all have loaded. One way to do this is to count the number of images you are loading, and then use the onload to count the number of images that have loaded. When the loaded count is the same as the loading count you know all have loaded and can then call a function to draw what you want with the images.
// Array of image names
const imageNames = "grass,hill,trees,sea,mountain,lake,volcano,shrine,outpost,civ".split(",");
const images = []; // array of images
const namedImages = {}; // object with named images
// counts of loaded and waiting toload images
var loadedCount = 0;
var imageCount = 0;
// tile sizes
const tileWidth = 20;
const tileHeight = 20;
// NOT SURE WHERE YOU GOT THIS FROM so have left it as you had in your code
// Would normally be from a canvas element via canvasElement.getContext("2d")
var ctx = myGameArea.context;
// seeded random function encapsulated in a singleton
// You can set the seed by passing it as an argument rand(seed) or
// just get the next random by not passing the argument. rand()
const rand = (function(){
const A = 8765432352450986;
const B = 8765432352450986; // This value should not be the same as A?? left as is so you get the same values
const M = 2576436549074795;
var seed = 1;
return (x = seed) => seed = ((A * x) + B) % M;
}());
// function loads an image with name
function addImage(name){
const image = new Image;
image.src = "textures/" + name + ".png";
image.onload = () => {
loadedCount += 1;
if(loadedCount === imageCount){
if(typeof allImagesLoaded === "function"){
allImagesLoaded();
}
}
}
imageCount += 1;
images.push(image);
namedImages[name] = image;
}
imageNames.forEach(addImage); // start loading all the images
// This function draws the tiles
function allImagesLoaded(){ /// function that is called when all the images have been loaded
var i, x, y, image;
for(i = 0; i < 256; i += 1){ // loop 16 by 16 times
ctx.drawImage(
images[Math.floor(rand()) % images.length]; //random function does not guarantee an integer so must floor
(i % 16) * tileWidth, // x position
Math.floor(i / 16) * tileHeight, // y position
tileWidth, tileHeight // width and height
);
}
}
So I am building a small game, and one of the characters is this Golem object:
function Golem(){
var self = this;
this.width = 470;
this.height = 360;
this.drawX = canvasEntities.width/3;
this.speed = 30;
this.isLeftKey = false;
this.isRightKey = false;
this.isSpacebar = false;
this.spritesheet = spritesheetgolemleft;
this.animate = function(){
requestAnimFrame(self.animate);
//this console log returns undefined
console.log(self.spritesheet)
this.spritesheet.update();
self.spritesheet.draw(self.drawX,canvasEntities.height/3);
}
}
the spritesheetgolemleft variable was already defined at the very top(global):
var spritesheetgolemleft = new SpriteSheet('images/golem_walkleft.png',470,360,3,6);
And here is the SpriteSheet class:
function SpriteSheet(path, frameWidth, frameHeight, frameSpeed, endFrame){
var image = new Image();
var framesPerRow,
currentFrame = 0,
counter = 0;
//# of frames after image loads
var self = this;
image.onload = function(){
framesPerRow = Math.floor(image.width/frameWidth);
};
image.src = path;
this.update = function(){
if(counter == (frameSpeed - 1))
currentFrame = (currentFrame + 1) % endFrame;
counter = (counter + 1) % frameSpeed;
}
this.draw = function(x,y){
var row = Math.floor(currentFrame / framesPerRow);
var col = Math.floor(currentFrame % framesPerRow);
//draw image into the Entities canvas
ctxEntities.drawImage(
image,
col * frameWidth, row*frameHeight,
frameWidth, frameHeight,
x,y,
frameWidth, frameHeight);
};
};
The error I am getting happens in the second to last line of the Golem() object:
this.spritesheet.update();
It is giving me a TypeError, cannot read property 'update' of undefined. Thinking it was some sort of issue with scopes, I added the self = this hack at the top, but it still does not work. What am I doing wrong? Thanks in advance.
It turns out that I was instantiating an object before creating the spritesheets. My mistake :/
Basically below is my script for a prototype which uses 128x128 tiles to draw a map on a canvas which user can drag to move around.
Script does work. However I have a few problems to be solved:
1. Poor performance and I can't figure out why.
2. I am missing a method to buffer the tiles before the actual drawing.
3. If you notice any other issues also that could help me to make things run more smoothly it would be fantastic.
Some explanations for the script:
variables
coordinates - Defines the actual images to be displayed. Image file names are type of '0_1.jpg', where 0 is Y and 1 is X.
mouse_position - As name says, is keeping record of mouse position.
position - This is a poorly named variable. It defines the position of the context drawn on canvas. This changes when user drags the view.
Any assistance would be appreciated greatly. Thank you.
var coordinates = [0, 0];
var mouse_position = [0, 0];
var position = [-128, -128];
var canvas = document.getElementById('map_canvas');
var context = canvas.getContext('2d');
var buffer = [];
var buffer_x = Math.floor(window.innerWidth/128)+4;
var buffer_y = Math.floor(window.innerHeight/128)+4;
var animation_frame_request = function() {
var a = window.requestAnimationFrame;
var b = window.webkitRequestAnimationFrame;
var c = window.mozRequestAnimationFrame;
var d = function(callback) {
window.setTimeout(callback, 1000/60);
}
return a || b || c || d;
}
var resizeCanvas = function() {
window.canvas.width = window.innerWidth;
window.canvas.height = window.innerHeight;
window.buffer_x = Math.floor(window.innerWidth/128)+4;
window.buffer_y = Math.floor(window.innerHeight/128)+4;
window.buffer = [];
for (row = 0; row < window.buffer_y; row++) {
x = [];
for (col = 0; col < window.buffer_x; col++) {
x.push(new Image());
}
window.buffer.push(x);
}
}
var render = function() {
animation_frame_request(render);
for (row = 0; row < window.buffer_y; row++) {
for (col = 0; col < window.buffer_x; col++) {
cy = window.coordinates[1]+row;
cx = window.coordinates[0]+col;
window.buffer[row][col].src = 'map/'+cy+'_'+cx+'.jpg';
}
}
for (row = 0; row < window.buffer_y; row++) {
for (col = 0; col < window.buffer_x; col++) {
window.context.drawImage(window.buffer[row][col],
window.position[0]+col*128,
window.position[1]+row*128, 128, 128);
}
}
}
var events = function() {
window.canvas.onmousemove = function(e) {
if (e['buttons'] == 1) {
window.position[0] += (e.clientX-window.mouse_position[0]);
window.position[1] += (e.clientY-window.mouse_position[1]);
if (window.position[0] >= 0) {
window.position[0] = -128;
window.coordinates[0] -= 1;
} else if (window.position[0] < -128) {
window.position[0] = 0;
window.coordinates[0] += 1;
}
if (window.position[1] >= 0) {
window.position[1] = -128;
window.coordinates[1] -= 1;
} else if (window.position[1] < -128) {
window.position[1] = 0;
window.coordinates[1] += 1;
}
render();
}
window.mouse_position[0] = e.clientX;
window.mouse_position[1] = e.clientY;
}
}
window.addEventListener('resize', resizeCanvas, false);
window.addEventListener('load', resizeCanvas, false);
window.addEventListener('mousemove', events, false);
resizeCanvas();
To get better performance you should avoid changing the src of img nodes and move them around instead.
A simple way to minimize the number of img nodes handled and modified (except for screen positioning) is to use an LRU (Least Recently Used) cache.
Basically you keep a cache of last say 100 image nodes (they must be enough to cover at least one screen) by using a dictionary mapping the src url to a node object and also keeping them all in a doubly-linked list.
When a tile is required you first check in the cache, and if it's already there just move it to the front of LRU list and move the img coordinates, otherwise create a new node and set the source or, if you already hit the cache limit, reuse the last node in the doubly-linked list instead. In code:
function setTile(x, y, src) {
var t = cache[src];
if (!t) {
if (cache_count == MAXCACHE) {
t = lru_last;
t.prev.next = null;
lru_last = t.prev;
t.prev = t.next = null;
delete cache[t.src]
t.src = src;
t.img.src = src;
cache[t.src] = t;
} else {
t = { prev: null,
next: null,
img: document.createElement("img") };
t.src = src;
t.img.src = src;
t.img.className = "tile";
scr.appendChild(t.img);
cache[t.src] = t;
cache_count += 1;
}
} else {
if (t.prev) t.prev.next = t.next; else lru_first = t.next;
if (t.next) t.next.prev = t.prev; else lru_last = t.prev;
}
t.prev = null; t.next = lru_first;
if (t.next) t.next.prev = t; else lru_last = t;
lru_first = t;
t.img.style.left = x + "px";
t.img.style.top = y + "px";
scr.appendChild(t.img);
}
I'm also always appending the requested tile to the container so that it goes in front of all other existing tiles; this way I don't need to remove old tiles and they're simply left behind.
To update the screen I just iterate over all the tiles I need and request them:
function setView(x0, y0) {
var w = scr.offsetWidth;
var h = scr.offsetHeight;
var iy0 = y0 >> 7;
var ix0 = x0 >> 7;
for (var y=iy0; y*128 < y0+h; y++) {
for (var x=ix0; x*128 < x0+w; x++) {
setTile(x*128-x0, y*128-y0, "tile_" + y + "_" + x + ".jpg");
}
}
}
most of the time the setTile request will just update the x and y coordinates of an existing img tag, without changing anything else. At the same time no more than MAXCACHE image nodes will be present on the screen.
You can see a full working example in
http://raksy.dyndns.org/tiles/tiles.html
I ran through this: PUZZLE CREATING TUTORIAL and completed the puzzle. I'm trying to have the same script run on more than one img on a page. I tried running some of it through a loop:
var i;
for(i=1; i<3; i++){
function init(){
_img = new Image();
_img.addEventListener('load', onImage, false);
_img.src = "images/"+i+".png"
}
function onImage(e){
_pieceWidth = Math.floor(_img.width / PUZZLE_DIFFICULTY)
_pieceHeight = Math.floor(_img.height / PUZZLE_DIFFICULTY)
_puzzleWidth = _pieceWidth * PUZZLE_DIFFICULTY;
_puzzleHeight = _pieceHeight * PUZZLE_DIFFICULTY;
setCanvas();
initPuzzle();
}
function setCanvas(){
_canvas = document.getElementById(""+i+"");
_stage = _canvas.getContext('2d');
_canvas.width = _puzzleWidth;
_canvas.height = _puzzleHeight;
_canvas.style.border = "2px solid red";
}
console.log(i);
}
and I've gotten to a point where I can print the 'i'th picture in the 'i'th canvas id, but it will only print one puzzle at a time and not more.
Everything in the puzzle code is not set up to handle multiple puzzles. You'll actually need to make way more changes than that to have the puzzle get rendered correctly.
What you should probably do is make a new makePuzzle function, that sets up variables for the rest of the functions to use, and then have them accept arguments, instead of relying on the things that are in the global scope..
for an example (This won't work unchanged, but should illustrate my point):
function makePuzzle(puzzleId, difficulty) {
var image = new Image();
image.addEventListener('load', function() {
makePuzzleForImage(image);
}, false);
image.src = "images/"+puzzleId+".png"
}
makePuzzleForImage(image) {
var pieceWidth = Math.floor(image.width / difficulty)
var pieceHeight = Math.floor(image.height / difficulty)
var puzzleWidth = pieceWidth * difficulty;
var puzzleHeight = pieceHeight * difficulty;
var canvas = document.getElementById(""+puzzleId+"");
var stage = canvas.getContext('2d');
canvas.width = puzzleWidth;
canvas.height = puzzleHeight;
canvas.style.border = "2px solid red";
// this also needs to be made so it can accept arguments, but I didn't
// do that for you since it'll take more time:
// initPuzzle();
}
for (var i=1; i<3; i++) {
makePuzzle(i, PUZZLE_DIFFICULTY);
}
var canvas = null;
var context = null;
var img = null;
var frames = [];
var assets = [];
var imgLoadCount = 0;
setup = function (fileArray) {
assets = fileArray;
//Loading an image
for(var i = 0; i < assets.length; i++) {
console.log(i);
frames.push(new Image()); // declare image object
frames[i].onload = onImageLoad(assets.length); //declare onload method
frames[i].src = URL.createObjectURL(assets[i]); //set url
}
};
onImageLoad = function (len) {
console.log("IMAGE!!!");
canvas = document.getElementById("my_canvas"); //creates a canvas element
context = canvas.getContext('2d');
canvas.width = window.innerWidth; //for full screen
canvas.height = window.innerHeight;
var x, y, numTilesRow;
numTilesRow = 10;
imgLoadCount++;
console.log("imgLoadCount = " + frames.length + ", length = " + len);
if(imgLoadCount != len) {
return;
}
for(var index = 0; index < len; index++) {
x = Math.floor((index % numTilesRow));
y = Math.floor(index / numTilesRow);
worldX = x * numTilesRow;
worldY = y * numTilesRow;
context.drawImage(frames[index], worldX, worldY);
}
};
I cant tell why drawImage has suddenly stopped working after inserting the code
if(imgLoadCount != len) {return;} that makes sure that all images are properly loaded. Would some one please help me find a solution to this problem.
You'll have to understand the difference between a function reference and a function call. The .onload property expects to be assigned with a function reference, but you assign it with the return value of the immediate(!) call to the function .onImageLoad. The difference is the parentheses ().
If you want to call a function with parameters as a callback to .onload, then you'd have to include it into an anonymous function (which itself is a function reference)
frames[i].onload = function() {onImageLoad(assets.length);};
With this, of course, you create a closure. This means that at the point of execution the onImageLoad() method will have access to the current value of assets.length (and not to the value at the point of assignment!). But in your case this doesn't make any difference, because assets.length never changes.