I have this code and in Firefox is working well, but in Chrome I'am getting this error:
"Uncaught Error: INVALID_STATE_ERR: DOM Exception 11" at sprites.js:36
on that line is this code:
context.drawImage(
Context is a global variable in which contains 2d context of canvas. Here is full code:
index.html
<!doctype html>
<html>
<head>
<meta charset="UTF-8">
<script type="text/javascript" src="sprites.js"></script>
<script type="text/javascript" src="game.js"></script>
<script type="text/javascript" src="prototypes.js"></script>
<script type="text/javascript" src="initialize.js"></script>
</head>
<body onload="initialize()">
</body>
</html>
sprites.js
function SpritePrototype(frames, width, height, type)
{
this.frames = frames;
this.type = type;
if (this.frames > 0) {
this.frameArray = new Array(this.frames);
for (var i = 0; i < this.frames; i++) {
this.frameArray[i] = document.createElement("canvas");
}
}
}
function Sprite()
{
this.id = 0;
this.prototype = 0;
this.next = 0;
this.prev = 0;
this.x = 0;
this.y = 0;
this.startFrame = 0;
this.currentFrame = 0;
}
Sprite.prototype.draw = function()
{
if (this.prototype == 0) {
return;
}
if (context.drawImage) {
if (this.prototype.frames > 0) {
context.drawImage(
this.prototype.frameArray[this.currentFrame],
Math.round(this.x),
Math.round(this.y)
);
}
}
}
game.js
function Game()
{
this.frameLength = 1000/30;
this.startTime = 0;
this.sprites = 0;
}
Game.prototype.resetTime = function()
{
var d = new Date();
this.startTime = d.getTime();
delete d;
}
Game.prototype.addSprite = function(prototype)
{
currentId++;
if (this.sprites == 0) { // if creating the first sprite
this.sprites = new Sprite();
this.sprites.id = currentId;
this.sprites.prototype = prototype;
} else {
var tempSprite = this.sprites; // temporarily store the first sprite
while (tempSprite.next != 0) { // while not the last sprite
tempSprite = tempSprite.next; // shift to next one
}
tempSprite.next = new Sprite(); // next sprite to the last sprite
tempSprite.next.id = currentId;
tempSprite.next.prototype = prototype;
tempSprite.next.next = 0; // the last sprite, or the last one in the space
tempSprite.next.prev = tempSprite;
}
}
Game.prototype.loop = function()
{
var tempSprite;
var currentTime;
var globalFrame;
var oldFrame;
var d = new Date();
currentTime = d.getTime();
delete d;
globalFrame = Math.floor((currentTime - this.startTime)/this.frameLength);
canvas.width = canvas.width;
tempSprite = this.sprites;
while (tempSprite != 0) {
if (tempSprite.frames > 0) {
oldFrame = tempSprite.currentFrame;
tempSprite.currentFrame = globalFrame;
}
tempSprite.draw();
tempSprite = tempSprite.next;
}
}
prototypes.js
var protoPlayer;
function createPrototypes()
{
var tempCtx;
var i;
protoPlayer = new SpritePrototype(5, 20, 30, "player");
for (i = 0; i < protoPlayer.frames; i++) {
protoPlayer.frameArray[i].width = protoPlayer.width;
protoPlayer.frameArray[i].height = protoPlayer.height;
tempCtx = protoPlayer.frameArray[i].getContext("2d");
tempCtx.strokeStyle = "rgb("+ i * 50 +", 0, 0)";
tempCtx.beginPath();
tempCtx.moveTo(0, 0);
tempCtx.lineTo(20, 30);
tempCtx.stroke();
}
}
initialize.js
var game;
var canvas;
var context;
var currentId;
function initialize()
{
canvas = document.createElement("canvas");
canvas.width = 640;
canvas.height = 480;
canvas.setAttribute("style", "background:#060606;");
document.body.appendChild(canvas);
context = canvas.getContext("2d");
createPrototypes();
currentId = 0;
game = new Game();
game.addSprite(protoPlayer);
game.loop();
}
Seems to me that that error is happening because you are calling drawImage with a HTMLCanvasObject who's height or width is zero. From the latest canvas 2d context spec:
If the image argument is an
HTMLCanvasElement object with either a
horizontal dimension or a vertical
dimension equal to zero, then the
implementation must raise an
INVALID_STATE_ERR exception.
http://dev.w3.org/html5/2dcontext/#images
Hope this helps.
Some time this error also occurred when we try to do document.getElemetnById('xx').innerHtml='htmlcode'; in this time 'htmlcode' should be proper formatted mean should use proper closing tags.
Related
I'm trying to understand javascript before going to jQuery and I made a simple image slider.
I ended up with the following code working well when I manually start it on browser console, and I can't figure out how to start it and if using Promise would do, and how.
Reduced code:
/*some variable declarations and value assignations*/
function cut(p1){
for (var i = 0; i < cuts; i++){
/*canvas working with path pattern and fill*/
slice[p1][i] = new Image();
slice[p1][i].src = canvas.toDataURL();
}
}
function slider(){
/*time based image selection and canvas clear*/
for (var i = 0; i < 10; i++){
y = /*timebased calc*/;
if(y<0){y=0;}
ctx.drawImage(slice[im][i], 0, y);
}
window.requestAnimationFrame(slider);
}
img[0].onload = function() {cut(0);};
img[1].onload = function() {cut(1);};
Full code:
var height = 500, width = 707, cuts = 10, cW = Math.ceil(width/cuts);
var img = [new Image(), new Image()];
var slice = [];
for (var i = 0; i < img.length; i++){
slice[i] = [];
}
var x = [];
for (var i=0; i<cuts; i++){
x[i]=Math.ceil(((i+1)*width)/cuts);
}
function cut(p1){
for (var i = 0; i < cuts; i++){
var canvas = document.createElement('canvas');
canvas.width = width;
canvas.height = height;
var context = canvas.getContext('2d');
var pat = context.createPattern( img[p1], 'no-repeat' );
context.fillStyle = pat;
context.beginPath();
context.moveTo(x[i], 0);
context.lineTo(x[i], height);
context.lineTo(x[i]-cW, height);
context.lineTo(x[i]-cW, 0);
context.closePath();
context.fill();
slice[p1][i] = new Image();
slice[p1][i].src = canvas.toDataURL();
}
}
var canv = document.createElement('canvas');
document.body.appendChild(canv);
canv.width = width;
canv.height = height;
var ctx = canv.getContext('2d');
var sTime= 0;
function slider(){
var t = (performance.now() - sTime) % 10000;
if(t%5000 === 2000){
ctx.clear();
}
var im = 0;
if(t >= 5000){
im = 1;
} else {
im = 0;
}
for (var i = 0; i < 10; i++){
t = t%5000;
y = 2000-((t)+(i*100));
if(y<0){y=0;}
ctx.drawImage(slice[im][i], 0, y);
}
window.requestAnimationFrame(slider);
}
CanvasRenderingContext2D.prototype.clear = function () {this.clearRect(0, 0, this.canvas.width, this.canvas.height);}
img[0].onload = function() {cut(0);};
img[1].onload = function() {cut(1);};
img[0].src = 'mountain.jpg';
img[1].src = 'beach.jpg';
Haven't tested this but it might come close:
function imageLoader(imagePaths, onLoad, onFinished) {
var images = [];
var arrayLength = imagePaths.length;
function callback() {
if(--arrayLength === 0) onFinished();
}
imagePaths.forEach(function(imagePath, index) {
var image = new Image();
image.onload(onLoad(index, callback));
image.src = imagePath;
images[index] = image;
});
return images;
}
modify cut() to:
function cut(p1, cb){
//.
//.
//.
cb();
}
replace
img[0].onload = function() {cut(0);};
img[1].onload = function() {cut(1);};
img[0].src = 'mountain.jpg';
img[1].src = 'beach.jpg';
with:
img = imageLoader(['mountain.jpg', 'beach.jpg'], cut, slider);
I am sure this is a very simple thing to do, but I am stuck here.
Here is the situation:
I have an HTML page with a div and a canvas element(not sure if I need this)
Also I have two javascript files using p5.js with setup and draw funtions where I draw my content on a canvas I create with createCanvas.
The other js file contains an object.
The problem is - I can get the animation to show on the HTML page, but not inside the div and/or canvas.
Image for a clearer picture:
HTML and JS comunication
HTML:
<html>
<head>
<meta charset="utf-8">
<title>Fractals</title>
<script language="javascript" type="text/javascript" src="libs/p5.js"></script>
<script language="javascript" src="libs/p5.dom.js"></script>
<script language="javascript" type="text/javascript" src="sketch.js"></script>
<script language="javascript" type="text/javascript" src="branch.js"></script>
<style>
body {
padding: 0;
margin: 0;
}
</style>
</head>
<body>
<div>
<canvas id="fractal" height="197" width="333" style=" width:333;height:197;"></canvas>
</div>
</body>
</html>
JS sketch:
var tree = [];
var x;
var y;
function setup() {
createCanvas(333,197);
var a = createVector(width / 2, height);
var b = createVector(width / 2, height - 50);
var root = new Branch(a, b);
tree[0] = root;
for (var t = 0; t < 5; t++) {
for (var i = tree.length-1; i >= 0; i--) {
if (!tree[i].finished){
tree.push(tree[i].branchA());
tree.push(tree[i].branchB());
tree.push(tree[i].branchC());
}
tree[i].finished = true;
}
}
}
function draw() {
background(51);
x = mouseX;
y = mouseY;
for (var i = 0; i < tree.length; i++) {
tree[i].show();
tree[i].wind(x, y, tree[i].end.x, tree[i].end.y);
}
}
JS branch object:
function Branch(begin, end) {
this.begin = begin;
this.end = end;
this.finished = false;
this.origx = this.end.x;
this.origy = this.end.y;
this.show = function() {
stroke(255);
line(this.begin.x, this.begin.y, this.end.x, this.end.y);
}
this.branchA = function() {
var dir = p5.Vector.sub(this.end, this.begin);
dir.rotate(19.2);
dir.mult(0.67);
var newEnd = p5.Vector.add(this.end, dir);
var v = new Branch(this.end, newEnd);
return v;
}
this.branchB = function() {
var dir = p5.Vector.sub(this.end, this.begin);
dir.rotate(0);
dir.mult(0.67);
var newEnd = p5.Vector.add(this.end, dir);
var v = new Branch(this.end, newEnd);
return v;
}
this.branchC = function() {
var dir = p5.Vector.sub(this.end, this.begin);
dir.rotate(-19.2);
dir.mult(0.67);
var newEnd = p5.Vector.add(this.end, dir);
var v = new Branch(this.end, newEnd);
return v;
}
this.wind = function(mox,moy,treex,treey) {
var d = dist(mox,moy,treex,treey);
if (d < 20) {
this.end.x += random(-0.3, 0.3);
this.end.y += random(-0.3, 0.3);
}else{
this.end.x = this.origx;
this.end.y = this.origy;
}
}
}
P5 libraries : https://p5js.org/download/
From the docs:
https://github.com/processing/p5.js/wiki/Positioning-your-canvas
// sketch.js
function setup() {
var canvas = createCanvas(100, 100);
// Move the canvas so it's inside our <div id="sketch-holder">.
canvas.parent('sketch-holder');
background(255, 0, 200);
}
Create one instance of canvas with P5, then assigns its parent by dom id.
currelty working on a small matching puzzle game. Currently it displays text for the time remaining and the number of tiles that have been macthes. I'm trying to create on for best completion time as well (How fast the person finishes the game) however have been running into a lot of problems. for two variables that I created "txt" and "matchesFoundText" when I type them the autocomplete box will popup and ".text" is displayed as one of the options so i would get something like "txt.text. however I'm not getting that option at all for "bestTimeTxt" and I have no idea as to why this is happening. I did all three variables the same way so I'm at a loss as to why Text is not available to select from for "bestTimeTxt". Here is my entire script.
<!DOCTYPE html>
<html>
<head>
<title>Recipe: Drawing a square</title>
<script src="easel.js"></script>
<script type="text/javascript">
var canvas;
var stage;
var squareSide = 70;
var squareOutline = 5;
var max_rgb_color_value = 255;
var gray = Graphics.getRGB(20, 20, 20);
var placementArray = [];
var tileClicked;
var timeAllowable;
var totalMatchesPossible;
var matchesFound;
var txt;
var bestTime;
var bestTimeTxt;
var matchesFoundText;
var squares;
function init() {
var rows = 5;
var columns = 6;
var squarePadding = 10;
canvas = document.getElementById('myCanvas');
stage = new Stage(canvas);
var numberOfTiles = rows*columns;
matchesFound = 0;
timeAllowable = 5;
bestTime = 0;
txt = new Text(timeAllowable, "30px Monospace", "#000");
txt.textBaseline = "top"; // draw text relative to the top of the em box.
txt.x = 500;
txt.y = 0;
bestTimeTxt = new Text(bestTime, "30px Monospace", "#000");
bestTimeTxt.textBaseLine = "top";
bestTimeTxt.x = 500;
bestTimeTxt.y = 80;
stage.addChild(txt);
stage.addChild(bestTimeTxt);
squares = [];
totalMatchesPossible = numberOfTiles/2;
Ticker.init();
Ticker.addListener(window);
Ticker.setPaused(false);
matchesFoundText = new Text("Pairs Found: "+matchesFound+"/"+totalMatchesPossible, "30px Monospace", "#000");
matchesFoundText.textBaseline = "top"; // draw text relative to the top of the em box.
matchesFoundText.x = 500;
matchesFoundText.y = 40;
stage.addChild(matchesFoundText);
setPlacementArray(numberOfTiles);
for(var i=0;i<numberOfTiles;i++){
var placement = getRandomPlacement(placementArray);
if (i % 2 === 0){
var color = randomColor();
}
var square = drawSquare(gray);
square.color = color;
square.x = (squareSide+squarePadding) * (placement % columns);
square.y = (squareSide+squarePadding) * Math.floor(placement / columns);
squares.push(square);
stage.addChild(square);
square.cache(0, 0, squareSide + squarePadding, squareSide + squarePadding);
square.onPress = handleOnPress;
stage.update();
};
}
function drawSquare(color) {
var shape = new Shape();
var graphics = shape.graphics;
graphics.setStrokeStyle(squareOutline);
graphics.beginStroke(gray);
graphics.beginFill(color);
graphics.rect(squareOutline, squareOutline, squareSide, squareSide);
return shape;
}
function randomColor(){
var color = Math.floor(Math.random()*255);
var color2 = Math.floor(Math.random()*255);
var color3 = Math.floor(Math.random()*255);
return Graphics.getRGB(color, color2, color3)
}
function setPlacementArray(numberOfTiles){
for(var i = 0;i< numberOfTiles;i++){
placementArray.push(i);
}
}
function getRandomPlacement(placementArray){
randomNumber = Math.floor(Math.random()*placementArray.length);
return placementArray.splice(randomNumber, 1)[0];
}
function handleOnPress(event){
var tile = event.target;
tile.graphics.beginFill(tile.color).rect(squareOutline, squareOutline, squareSide, squareSide);
if(!!tileClicked === false || tileClicked === tile){
tileClicked = tile;
tileClicked.updateCache("source-overlay");
}else{
if(tileClicked.color === tile.color && tileClicked !== tile){
tileClicked.visible = false;
tile.visible = false;
matchesFound++;
matchesFoundText.text = "Pairs Found: "+matchesFound+"/"+totalMatchesPossible;
if (matchesFound===totalMatchesPossible){
gameOver(true);
}
}else{
tileClicked.graphics.beginFill(gray).rect(squareOutline, squareOutline, squareSide, squareSide);
}
tileClicked.updateCache("source-overlay");
tile.updateCache("source-overlay");
tileClicked = tile;
}
stage.update();
}
function tick() {
secondsLeft = Math.floor((timeAllowable-Ticker.getTime()/1000));
txt.text = secondsLeft;
;
if (secondsLeft <= 0){
gameOver(false);
}
stage.update();
}
function gameOver(win){
Ticker.setPaused(true);
for(var i=0;i<squares.length;i++){
squares[i].graphics.beginFill(squares[i].color).rect(5, 5, 70, 70);
squares[i].onPress = null;
if (win === false){
squares[i].uncache();
}
}
var replayParagraph = document.getElementById("replay");
replayParagraph.innerHTML = "<a href='#' onClick='history.go(0);'>Play Again?</a>";
if (win === true){
matchesFoundText.text = "You win!"
}else{
txt.text = secondsLeft + "... Game Over";
}
}
function replay(){
init();
}
</script>
</head>
<body onload="init()">
<header id="header">
<p id="replay"></p>
</header>
<canvas id="myCanvas" width="960" height="400"></canvas>
</body>
</html>
Okay so apparently the reason why I was having issues is because the x and y positions of the bestTimeTxt variable was causing it to be obscured by the position of everything else.
I'm trying to create the following animation:
- when the page loads, I load the 2 components of my logo and draw them onto the canvas
- after clicking the animate button, both images should smoothly move up to the top of the page and shrink
However, it seems that the drawImage() only takes place somewhere after the entire animation has been completed even though I can see it being executed at the right time in the console. Commenting out the clearRect function also shows me that every frame is actually drawn onto the screen, but sadly they all appear together after the animation should be completed.
I'm pretty new to canvases and relevant tutorials on such animations are scarce and don't get me much further.
Here's the relevant script:
<script type="text/javascript">
var logoCanvas;
var logoContext;
var direction = 1;
var logoAnimationDuration = 2000; //millisec
var frameSpeed = 30/1000; //frames per second
var logoImageRatio = 0;
var logoTextRatio = 0;
var initialLogoImageHeight = 0;
var initialLogoTextHeight = 0;
var initialLogoImageTop = 0;
var initialLogoImageLeft = 0;
var initialLogoTextTop = 0;
var initialLogoTextLeft = 0;
var newLogoImageLeft = 0;
var logoImageWidth = 0;
var logoImageHeight = 0;
var logoTextWidth = 0;
var logoTextHeight = 0;
var logoImageTop = 0;
var logoImageLeft = 0;
var logoTextTop = 0;
var logoTextLeft = 0;
var logoImageLoaded = false;
var logoTextLoaded = false;
var logoImage = new Image();
var logoText = new Image();
function AnimateFrontPageCanvas() {
if(logoCanvas.height <= $('#Page_0').height()) {
logoCanvas.height = $('#Page_0').height();
return;
}
if(logoImageHeight <= $('#Page_0').height() - 4) {
return;
}
if(logoImageTop <= 2) {
return;
}
//logoCanvas.height = parseFloat(logoCanvas.height) - (parseFloat(window.innerHeight) - parseFloat($('#Page_0').height())) * 1/frameSpeed * 1/logoAnimationDuration;
logoContext.clearRect(0, 0, logoCanvas.width, logoCanvas.height);
AnimateLogo();
setTimeout(AnimateFrontPageCanvas(), 1/frameSpeed);
}
function AnimateLogo() {
AnimateLogoImage();
AnimateLogoText();
}
function AnimateLogoImage() {
logoImageHeight = logoImageHeight - (initialLogoImageHeight - $('#Page_0').height() + 4) * (1/frameSpeed) * (1/logoAnimationDuration);
logoImageWidth = logoImageHeight*logoImageRatio;
logoImageTop = logoImageTop - (initialLogoImageTop - 2)*(1/frameSpeed) * (1/logoAnimationDuration);
logoImageLeft = logoImageLeft - (initialLogoImageLeft - newLogoImageLeft) * (1/frameSpeed) * (1/logoAnimationDuration);
logoContext.drawImage(logoImage, logoImageLeft, logoImageTop, logoImageWidth, logoImageHeight);
var time = new Date();
time = time.getTime();
console.log('logoimage drawn: ' + time);
}
function AnimateLogoText() {
logoTextHeight = logoTextHeight - (initialLogoTextHeight - $('#Page_0').height() + 4) * (1/frameSpeed) * (1/logoAnimationDuration);
logoTextWidth = logoTextHeight*logoTextRatio;
logoTextTop = logoTextTop - (initialLogoTextTop - 2) * (1/frameSpeed)*(1/logoAnimationDuration);
logoTextLeft = logoTextLeft - (initialLogoTextLeft - newLogoTextLeft)*(1/frameSpeed)*(1/logoAnimationDuration);
logoContext.drawImage(logoText, logoTextLeft, logoTextTop, logoTextWidth, logoTextHeight);
var time = new Date();
time = time.getTime();
console.log('logotext drawn: ' + time);
}
function InitiateFrontPageCanvas() {
logoImage.onload = function() {
logoImageLoaded = true;
AfterImagesLoadedActions();
}
logoImage.src = '/site_mats/images/logo_image.png';
logoText.onload = function() {
logoTextLoaded = true;
AfterImagesLoadedActions();
}
logoText.src = '/site_mats/images/logo_text.png';
}
function AfterImagesLoadedActions() {
if(logoImageLoaded && logoTextLoaded) {
logoImageRatio = logoImage.width/logoImage.height;
logoTextRatio = logoText.width/logoText.height;
if(logoImage.width > 0.8*logoCanvas.width) {
logoImage.width = 0.8*logoCanvas.width;
logoImage.height = logoImage.width/logoImageRatio;
}
if(logoText.width > 0.8*logoCanvas.width) {
logoText.width = 0.8*logoCanvas.width;
logoText.height = logoText.width/logoTextRatio;
}
if(parseFloat(logoImage.height) + parseFloat(logoText.height) > 0.66*logoCanvas.height) {
var x = (0.66*logoCanvas.height)/(parseFloat(logoImage.height) + parseFloat(logoText.height));
logoImage.height = x*logoImage.height;
logoImage.width = logoImage.height*logoImageRatio;
logoText.height = x*logoText.height;
logoText.width = logoText.height*logoTextRatio;
}
initialLogoImageHeight = logoImage.height;
initialLogoTextHeight = logoText.height;
logoImageHeight = logoImage.height;
logoImageWidth = logoImage.width;
logoTextHeight = logoText.height;
logoTextWidth = logoText.width;
initialLogoImageTop = parseFloat((logoCanvas.height-(parseFloat(logoImageHeight)+parseFloat(logoTextHeight)))/2);
initialLogoImageLeft = parseFloat((logoCanvas.width-logoImageWidth)/2);
initialLogoTextTop = parseFloat(((logoCanvas.height-(parseFloat(logoImageHeight)+parseFloat(logoTextHeight)))/2)+parseFloat(logoImageHeight));
initialLogoTextLeft = parseFloat((logoCanvas.width-logoImageWidth)/2);
logoImageTop = initialLogoImageTop;
logoImageLeft = initialLogoImageLeft;
logoTextTop = initialLogoTextTop;
logoTextLeft = initialLogoTextLeft;
newLogoImageLeft = parseFloat(2);
newLogoTextLeft = parseFloat((logoCanvas.width-$('#Page_0').height()*logoTextRatio)/2);;
logoContext.drawImage(logoText, logoTextLeft, logoTextTop, logoTextWidth, logoTextHeight);
logoContext.drawImage(logoImage, logoImageLeft, logoImageTop, logoImageWidth, logoImageHeight);
//remove onload from image objects
logoImage.onload = null;
logoText.onload = null;
}
}
function SetFrontPageCanvas() {
logoCanvas = document.getElementById('LogoCanvas');
logoContext = logoCanvas.getContext('2d');
logoCanvas.width = window.innerWidth;
logoCanvas.height = window.innerHeight;
logoContext.clearRect(0, 0, logoCanvas.width, logoCanvas.height);
InitiateFrontPageCanvas();
}
window.onload = function() {
SetFrontPageCanvas();
};
$(document).ready(function() {
windowWidth = $(window).width();
windowHeight = $(window).height();
});
$(window).resize(function() {
//alert($(window).width() + ' - ' + $(window).height());
logoImageLoaded = false;
logoTextLoaded = false;
SetFrontPageCanvas();
windowWidth = $(window).width();
windowHeight = $(window).height();
});
</script>
And here's the relevant html:
<canvas id="LogoCanvas" style="position:absolute;top:0;left:0;z-index:1;"></canvas>
<div id="Page_0" style="position:absolute;top:0;left:0;z-index:5;width:100%;height:90px;">
<div align="center" style="position:fixed;bottom:5px;z-index:100;width:100%;">
<input type="button" onClick="AnimateFrontPageCanvas()" value="Animate">
</div>
If desired, the code can also be seen in action here: http://villa-gloria-katouna.com/site_mats/animation.php
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