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JavaScript - How To Refresh Or Redraw Canvas In Javascrpt?
I want to redraw or refresh my Canvas in Javascript.
How to do it? Similar Tutorialsi now have <a href=""javascript:NewCssCal('repaymentdate','ddMMyyyy')""> how can I have this after it calls teh newcsscal and fills in the textbox call another function. (i don't want to add it to newcsscal as that's used in multiple locations and I only need to call this function in 1 location. I currently have a friends.php page, which outputs a list of a logged-in members friends. Next to each friends is a link to delete a friend: Code: <a href="wipecontact.php?f_id=' . $fid . '&m_id=' . $logOptions_id . '">Delete Friend</a> The wipecontact.php is just pure code that deletes the relationship from a MySQL table and looks like this: Code: include_once "scripts/connect_to_mysql.php";
if (($_GET['f_id']) && ($_GET['m_id'])) {
$f_id = $_GET['f_id'];
$m_id = $_GET['m_id'];
$del_friend = 'mysql_query("DELETE FROM friends WHERE (($f_id IN (requesting_id, requested_id)) AND ($m_id IN (requesting_id, requested_id)))") or die (mysql_error())';
} else {
echo"something went wrong with deleting your friend :(";
exit();
}
?>
Everything works fine, but how can I add a javascript (or jquery etc.) pop-up that lets the user confirm the deletion before proceeding to the MySQL delete query. I am just looking for something simple, without having to alter my code too much. Note that I need the pop-up to come up before running the mysql query! I'm having trouble getting around this. I'm sort of new to javascript, but I can read it when its all put together. Thanks. Hi, I'm trying to update an element on my page after every iteration of a loop. I'm using a simple innerHTML to achieve this, however, what happens is the page freezes during the entirety of the loop, and finally updates when the loop finishes. PHP Code: // below function is triggered by clicking some element function go() { for (var i = 1; i < len; ++i) { document.getElementById("output").innerHTML += "Processing #" + i; doStuff(); } } Ideally, I'd like the output to update and scroll down as the function processes the data. Is the problem that innerHTML can't keep up with the speed at which the for loop progresses? Just wondering if it's possible to prevent a page displaying until the content is fully loaded. I have a form with a load of check boxes that reloads itself on each user click and it would be nice to smooth things out a little, e.g. hold a screenshot of the page until the reload is complete and then instantly show that one. Stupid question? Cheers, Nick Hi, I have the below code: Code: <script type="text/javascript">
function loadQuickMessageCheck(File,ID){
var xmlhttp;
if (window.XMLHttpRequest) {
xmlhttp=new XMLHttpRequest();
}
else {
xmlhttp=new ActiveXObject("Microsoft.XMLHTTP");
}
xmlhttp.onreadystatechange=function(){
if (xmlhttp.readyState==4 && xmlhttp.status==200){
document.getElementById(ID).innerHTML=xmlhttp.responseText;
eucalyptus = setInterval(function(){loadQuickMessageCheck(File,ID)},20000);
}
}
xmlhttp.open("POST",File,true);
xmlhttp.send();
}
</script>
But I am overloading the server and crashing it. I've googled the issue and have found people with similar problems who talk about the need to cancel the last refresh request before they send the next refresh. I even found this nice piece of code which worked for someone else. Quote: try{window.clearTimeout(tRefresh)} catch(err) {} tRefresh = setInterval(setContext, varInterval*60*1000); } I am not sure if this is the solution that I am looking for but if it is all my attempts at applying this code has been a bit of a disaster. Hi there! How should I write this - better than it's now - so that when I rotate a figure, in the next "frame" it would stay rotated? Second thing - if you run this code, and set the angle for, let's say 180 degrees the figure is being drawn in some random location. How do I fix this? Code: Code:
function GenericFigure(context) {
this.states = ["wait", "moving", "rotating", "stop"];
this.state = this.states[0];
this.ctx = context;
this.sqrW = this.sqrH = 20;
this.ctxW = 200;
this.ctxH = 350;
this.colorsO = {
red : "#ee1515",
green : "#45d137",
blue : "#17a3f3",
orange : "#ff910f",
purple : "#680077"
};
this.colorsA = ["#ee1515", "#45d137", "#17a3f3", "#ff910f", "#680077"];
this.pickColor = function() {
var num = Math.floor(Math.random() * 5);
return this.colorsA[num];
}
}
function Rectangle(context) {
this.inheritFrom = GenericFigure;
this.inheritFrom(context);
this.width = this.sqrW;
this.height = this.sqrH * 3;
this.x = this.ctxW / 2;
this.y = 0;
this.rotation = -1;
this.setRotation = function(angle) {
this.rotation = angle;
}
this.rotate = function() {
this.ctx.clearRect(0, 0, this.ctxW, this.ctxH);
this.ctx.translate(this.x + 2 * this.width, this.y - 2 * this.height + 20);
this.ctx.rotate(this.rotation * Math.PI / 180);
this.ctx.fillRect(this.ctxW / 2, 0, this.width, this.height);
this.ctx.restore();
}
this.moveDown = function() {
this.y += 20;
this.ctx.restore();
this.ctx.clearRect(0, 0, this.ctxW, this.ctxH);
this.ctx.fillRect(this.x, this.y, this.width, this.height);
this.ctx.save();
if(this.rotation > -1) {
this.rotate();
}
l("A");
}
this.draw = function() {
this.ctx.fillStyle = this.pickColor();
this.ctx.save();
this.ctx.fillRect(this.x, this.y, this.width, this.height);
}
}
//a tak można wywołać:
var ctx = document.getElementById("game").getContext("2d");
var rect = new Rectangle(ctx);
rect.draw();
var inte = setInterval(function(){if(rect.y >= rect.ctxH - rect.height){clearInterval(inte);return;}if(rect.y == 60) rect.setRotation(90);rect.moveDown();}, 500);
And the third problem: Code: this.ctx.translate(this.x, 0); I thought, that this line should set orientation point to top left corner of my figure, but it seems, that it doesn't - after rotation my figure is being drawn two heights lower. Again - how do I fix it? Any help will be much appreciated . Hey everyone, I have been practicing using canvas to make designs. My current code below will load the word the user inputs and makes it bounce around the canvas as well as a text spinner. However, whenever the user inputs a second word, the bounce below stops to start a new one and the text spinner messes up. I was wondering if anyone could help me so when the user inputs another word, that it either reloads a new textspinner or adds another one, as well as just add the word to the canvas without stopped the old one. Here's my current script. Thanks already, Joey Code:
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<script>
var ctx;
var a=0.0;
var as=true;//true a is increasing, false decreasing
var x,y;
var xs = 1;
var ys = 1;
var userWord
var myDiv, t;
var test = 0;
var ds ="";//display string
var sli =0; //spinning letter index;
function init(){
ctx = document.getElementById("myCvs").getContext("2d");
userWord = document.getElementById("userWord").value;
x=Math.floor(Math.random()*801)
y=Math.floor(Math.random()*601);
drawText();
setInterval("onEnterFrame()", 50);
myDiv = document.getElementById("myDiv");
for (i =0; i<=userWord.length;i++){
ds += "*";
}
myDiv.innerHTML =ds;
textSpin();
}
function textSpin(){
myChar = randomChar();
var newString = userWord.slice(0, sli);
newString +=myChar;
newString += ds.slice(sli+1, ds.length-1);
myDiv.innerHTML = newString;
if (myChar == userWord.charAt(sli)){sli++;}
if (sli<userWord.length){
t = setTimeout("textSpin()", 80);
}
}
function randomChar(){
var rc = Math.random()*26 + 97; //random lowercase char code
return String.fromCharCode(rc);
}
function onEnterFrame(){
if(a>1){as = false;}
if(a<0){as = true;}
if(as){
a+=0.01;
}else{
a-=0.01;
}
if(x>800){xs = -1}
if(x<0){xs=1}
if(y>600){ys = -1}
if(y<0){ys=1}
x+=10 *xs;
y+=10 *ys;
drawText();
}
function drawText(){
ctx.font = "20px Times New Roman";
//ctx.fillStyle= "rgb(256,256,256)";
//ctx.fillText("Hello", x, y);
ctx.fillStyle = randomColor();
ctx.fillText(userWord, x,y);
}
function randomColor(){
var r = Math.floor(Math.random()*150)+55;
var g = Math.floor(Math.random()*256)+150;
var b = Math.floor(Math.random()*20)+50;
var a = Math.random();
return "rgba("+ r+ ","+g+","+b+","+ a+")";
}
//function randomFont(){
// var s = Math.floor(Math.random()*100) +100;
// return s; //+ "px Times New Roman";}
</script>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<style type="text/css">
body {
background-color:#000;
}
#myDiv {
color:#FFF;
}
</style>
</head>
<body onLoad=""><center>
<input type="text" id="userWord" value=""> </input><br>
<input type="button" id="enterWord" value="Enter Word" onClick="init()" ></input><br><br>
<div id="myDiv" > </div>
<canvas id="myCvs" width="800px" height="600px" /><br>
<br>
</center>
</body>
</html>
I've been reading a lot of tutorials on the canvas tag and seen a lot of people using JavaScript that looks something like: ctx.beginPath(); ctx.moveTo(25,25); ctx.lineTo(105,25); ctx.fill(); I understand that ctx is just the variable name and I can replace that with any variable I define, however, I'm looking for a list of all of the methods such as (moveTo, lineTo, fill etc...), as well as what they do. I hope I'm explaining this or asking this correctly. Thanks! -Mike Hello guys! I need your help! I want to create a rectangle with a line in the middle with the canvas object. The problem is that the line in the middle gets bigger than the rest of the rectangle. How do I solve this? I believe it has something to do with shadows. If so, how do I turn them off. My code is: <html> <head> <title></title> </head> <body> <canvas id='chart' width='400' height='200'> <script type="text/javascript"> var canvas = document.getElementById('chart'); var ctx = canvas.getContext('2d'); ctx.lineWidth = 10; ctx.strokeRect(0, 0, 400, 200); ctx.moveTo(0, 100); ctx.lineTo(400, 100); ctx.stroke(); </script> </body> </html> So I've been making a game using html canvas. Here is a link to the game. (Move around with wasd, rotate turret with left and right arrows) http://db.tt/ei3LlR The problem is that the shadow flickers when it is rotated. This does not happen in firefox. The shadow is not an image, but another canvas element, generated dynamically from the image of the tank. So the problem seems to be with webkit drawing rotated canvas elements inside another. Could this possibly be the reason behind this, or is it more likely to be a problem on my end? Anyone got any suggestions on techniques? The main one I find is to use translate to move the canvas around, which just seems odd to me. I don't even fully understand how it works. But the one I was looking at used clearRect. In examples given looked as though it had to redraw the canvas every frame. I'm just mucking around with a simple poker game, figured i'd have the table in one layer and anything that moves on a top layer? By doing that I could only clear each card as it moved around...yes? Anyone know of a better way of doing things? Code: <form>
<input id="a" size=4 name="neg" placeholder="1st Screen size in inch">
<input id="b" size=4 name="hoyr" placeholder="2nd Screen size in inch">
<input type="submit" value="GO!" onclick="getValue()">
</form>
</div>
<canvas id="MyCanvas" width="1000" height="1000"></canvas>
<script type="text/javascript">
function getValue()
{
var x = document.getElementById("a").value;
var y = document.getElementById("b").value;
var aWidth;
var aHeight;
var bWidth;
var bHeight;
var c= document.getElementById("MyCanvas");
var ctx= c.getContext("2d");
ctx.fillStyle="#4AA02C";
ctx.fillRect(0,0,x,y);
}
Here, it draws canvas then disappears immediately. I just cant wrap my mind around canvas. As far as I can tell theres no logical reason as to why the code would not work. Could someone take a look at it and possibly figure out whats wrong? I'm trying to intialize and draw a canvas with a simple image. I have the functions in a custom namespace in javascript. I am also using Jquery Code: var birdr = new Image();
var birdl = new Image();
$(document).ready(function(){
if(Modernizr.canvas){
var c = document.createElement('canvas');
LK.animLoad();
document.getElementById('backg-canvas').appendChild(c);
$('canvas').attr({'width':'500','height':'500','id':'canvas'});
var context = LK.returnCanvas();
context.drawImage(birdl, 400,487,10,10);
}
});
var LK = {
birdx: 400, //unused (lets just get it to draw the image first :\)
birdy: 487, //unused
animLoad: function(){
birdl.src = "images/bird2.png";
birdr.src = "images/bird.png";
//alert(birdl);
//alert(birdr);
},
returnCanvas: function(ca){
var b_canvas = LK.getCanvas();
var b_context = b_canvas.getContext('2d');
return b_context;
},
getCanvas: function(){
var a_canvas = document.getElementById('canvas');
//alert(a_canvas);
return a_canvas;
}
}
Any help would be greatly appreciate thanks. Btw safari web inspector indicates the canvas is getting properly created and appended to the container div. So that all works fine. So I'm creating a game and decided to use a canvas for the map. The map is a big pictures 500kb+ (6400x6400px) and the canvas size is 320x320 so I am displaying only part of the image at a time and have the page reload on button click for database purposes. What I'd like help with is performance. Currently it's taking a few secs to reload every time and it seems that it causes some cpu strain (can't switch tabs while loading). Could I stop the canvas from reloading the image each time the page is reloaded and if so then how? Can I make the canvas only load a part of the image, if so then how? If neither is possible any tips, solutions how to solve the performance issues? I have make a javascript program that uses HTML canvas and I can't get it to work in Internet Explorer. I tried using excanvas and jqcanvas but had trouble getting them to work. Does anyone know how to do this?
Hi. I'm writing a script that graphs data in different colors and shapes and I'm encountering two problems: (1) I can't specify different colors for the graph I'm rendering. If I use fillStyle="red"; then the entire chart becomes red. It seems to use the last color specified as the color for everything on the chart. (2) The shapes are overlapping in strange ways. The fills are not covering the lines of shapes behind them so it's unclear which shape is in front and which is behind. It's like they aren't being treated as separate shapes but instead one shape where boundaries are unclear. I don't know how else to explain it. I'm hoping there is some way to put each shape in its own layer. Would I have to use DIV IDs for that or is there a way to keep it all in the script so it's more scalable? I guess canvases like inline width/height instead of css width/height. This solved the issue. I'm working on a project that uses HTML5 Canvas and I'm having a strange problem with stretching. I noticed it with images and thought my math might have been wrong but then I took everything out and tried drawing a simple 100x100 square and it's completely stretched out at different proportions. The code for this (small class code)- Code: function Canvas(DOMID, F)
{
this.Frame = null;
this.width = null;
this.height = null;
this.zoom = null;
this.DOM = null;
this.ctx = null;
this.offset = null;
//Constructor
this.init = function(DOMID, F)
{
this.DOM = document.getElementById(DOMID);
this.width = $(this.DOM).width();
this.height = $(this.DOM).height();
this.ctx = this.DOM.getContext("2d");
this.zoom = 1;
this.offset = {x:0,y:0};
if(F != null)
this.setFrame(F);
this.onReady();
}
//Modifiers
this.draw = function()
{
//this.ctx.drawImage(image, 0, 0);
this.ctx.beginPath();
this.ctx.fillStyle = "#ffffff";
this.ctx.rect(0,0,100,100);
this.ctx.closePath();
this.ctx.fill();
}
this.setFrame = function(F)
{
this.Frame = F;
}
//Events
this.onReady = function(){}
this.init(DOMID, F);
}
The code calling this function is in an interval- Code: window.goToCanvas = function()
{
clearTimeout(playInterval);
playInterval = setInterval("drawCurrentCanvas()", window.playSpeed);
}
window.drawCurrentCanvas = function()
{
index = window.canvasIndex;
canvases[index].draw();
}
The page can be found here- http://micahwilliams...ewer/viewer.php I'm stumped. I hope someone can see my mistake somewhere. i want to transfrom image like the picture below using canvas,it seems simple but i find no way to do , can anyone give me some ideas? ( left side is the source) not sure if this is the right place to ask canvas questions, but if it is, i'm trying to program a game like air hockey (with some twists). it works pretty well now but the table is viewed from overhead, and i would prefer to show the game from the player's perspective, as in the pic, without having to rewrite my existing code. anyone know of any js libraries or formulas which can accomplish this? Hi there! I found this code, in reply to someone's problem, on this forum. I have altered it to my own needs, as it's an excellent piece of code. However, I would like it to run under HTML5. I believe I need to add "canvas" code to do the same?? I have already changed the doctype! HTML heading etc., Can anyone help? Many, many thanks!! Code: <!doctype html>
<head>
<meta charset=UTF-8" />
<title>Crazy Rally - France</title>
<script type="text/javascript">
var frames = new Array();
//load frames into array
for(var i = 1; i < 417; i++){
frames[i] = new Image(480,320);
frames[i].src = "track" + i + ".png";
}
//playback
var currentFrameNumber = 1;
var fps = 30; // frames / second
const speed = 1000 / fps; // milliseconds
//var speed = 33;
function nextFrame( )
{
document.getElementById("display").src = frames[currentFrameNumber].src;
currentFrameNumber = ( currentFrameNumber + 1 ) % frames.length;
setTimeout( nextFrame, speed );
}
window.onload = nextFrame;
</script>
</head>
<body>
<img id="display" src="track1.png" width="480" height="320">
</body>
</html>
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