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JavaScript - Can Canvas Transform Image Like This?
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) Similar Tutorialsnot 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? I found a great little starfield script made with javascript and canvas3d. however i can't for the life of me figure out how to implement a background image inside the canvas. is there some command that tells it to use some feature of canvas, that if otherwise not called, won't allow normal graphics? his whole starfield is generated with a search engine form , and appears to just use a text period to represent stars. here's a link to his script: http://seb.ly/demos/canvas3d/canvas3d2.html how do i get a background image in that? or is it impossible? i tried putting it in the body tag, but it just flashed the background image on the screen for a half a second and then went back to showing only the black background. i tried removing the background body color and replacing it with only background-image ccs, same problem. i tried div positioning it, but the div just covered up the starfield. 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 am very new to javascript(and these forums) and I am teaching my self to use the canvas element. I am trying to draw an image to the canvas but nothing is appearing. And I am getting no error in the chrome console. Can anyone see why? Code:
function RPGanimation(options)
{
this.initcanvas(options);
this.initbackground(options);
};
RPGanimation.prototype = {
initbackground: function(options){
this.background = new Image();
this.background.src = options.backsource;
this.background.onload = this.drawbackground();
},
initcanvas:function(options){
this.canvas = document.getElementById(options.canvasid);
this.context = this.canvas.getContext('2d');
this.dimensions = {width:this.canvas.width,height:this.canvas.height};
},
drawbackground:function(){
//document.write('<IMG SRC="Chrysanthemum.jpg">');
this.context.drawImage(this.background,0,0,this.dimensions.width,this.dimensions.height);
}
};
I create the object in a webpage with the canvas element created just before that script tag... Hello all; I am trying to load four images into a canvas using an array. The images load fine and all, however they are resizing weird. I haven't specified what I want them to resize to, as the actual image are already the sizes I want. However when loaded into the canvas they are sizing differently then their actual sizes. Even when I specify their actual size in the code, they still resize weirdly. Here is my code: Code: <body>
<canvas id="worldscreen" class="map"></canvas><br />
<script type="text/javascript">
function loadImages(arrow, call) {
var images = {};
var loaded = 0;
var num = 0;
for (var src in arrow) {
num++;
}
for (var src in arrow) {
images[src] = new Image();
images[src].onload = function(){
if (++loaded >= num) {
call(images);
}
};
images[src].src = arrow[src];
}
}
window.onload = function(images) {
var canvas = document.getElementById("worldscreen").getContext("2d");
var arrow = {
top: "sideQUEST/images/arrow-top.png",
right: "sideQUEST/images/arrow-right.png",
bottom: "sideQUEST/images/arrow-bottom.png",
left: "sideQUEST/images/arrow-left.png",
};
loadImages(arrow, function(images) {
canvas.drawImage(images.top, 100, 18);
canvas.drawImage(images.right, 215, 36);
canvas.drawImage(images.bottom, 100, 115);
canvas.drawImage(images.left, 36, 36);
});
};
</script>
</body>
You can see the code in action he http://myrmidon16.x10.mx/test.php. This is very frustrating and if you have any suggestions it would be greatly appreciated. Thank you. Hi everyone, I am trying to make an image mask using javascript. The basic idea is that the image on the canvas will appear as a black box. When the user hovers over the image a small part of it is revealed. I have attached a picture as an example because its quite hard to explain! Any help would be appreciated! Thanks, Luke Okay, so I have a canvas, and I want the user to be able to copy an image url and paste it into an input box, that will then set it as the canvas background image. Does anyone know how I can do this? I was thinking about using the OnChange method in the text input, but I cannot find any help with that online. My current Canvas Background is (In <head><script>) Code: var imgObg = new Image(); imageObj.src = "images/bg.png"; And my text input is Code: <form name="input" action="" method="get"> <input type="text" id="textboxBG" onchange="??" /> <input type="submit" value="Submit" /> </form> If you need more code, or would like to help me out more in depth, I would gladly paypal you a little money. I know this can't be too difficult! I REALLY want this done! Hello, I have the code in the annexe wich is working but grossly redondant, clearly, I would like to have only one function toggleEditor(), that would manage the global variables editInstance with a parameter or something equivalent to avoid having 2 twin like functions. Thanks for your suggestions. HJS Annexe : Code:
<html>
<body>
<script src="../flovinax.js" type="text/javascript"></script>
<script>
var editInstance= null;
function toggleEditor1(edtN) {
if(editInstance===null) {
editInstance = new flovinaxa({fullPanel : true}).panelInstance(edtN);
} else {
editInstance.removeInstance(edtN);
editInstance= null;
}
}
var editInstance2= null;
function toggleEditor2(edtN) {
if(editInstance2===null) {
editInstance2 = new flovinaxa({fullPanel : true}).panelInstance(edtN);
} else {
editInstance2.removeInstance(edtN);
editInstance2= null;
}
}
</script>
<div>
<textarea style="width: 800px; height: 200px;" id="myArea"></textarea>
<br />
<button onClick="toggleEditor1('myArea');">+</button>
</div>
<div style="clear: both;"></div>
<div>
<textarea style="width: 800px; height: 200px;" id="myArea2"></textarea>
<br />
<button onClick="toggleEditor2('myArea2');">+</button>
</div>
<div style="clear: both;"></div>
</body>
</html>
Hi, I currently have a <p> where it changes to a textarea when a button is clicked How do I preserve the whitespace when saving that text to a database and displaying back to a <p>? Hi, Is it possible that when a webpage loads I can have javascript change the class of a div from: .up { transform: translate(0px,-500px) transition: all 5s ease-in; } to .down { transform: translate(0px,0px) transition: all 5s ease-in; } Essentially I would like a div to move down into place from the top of screen to the middle of screen after the page has loaded. Some thing like this?: Code: <script type="text/javascript">
function transform()
{
document.getElementById("content").className = "down";
</script>
<div id="content" class "up" onload="transform()">
</div>
</html>
would this work or is there a better way? Adrian. 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 . 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 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>
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? 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> 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. 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? 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. Hello, I have this idea, but I wouldn't want to reinvent the wheel if it's already been done. I want to generate perspective grid on canvas depending on browser window size, something like this, but without textures: http://www.123rf.com/photo_2651286_a...rspective.html Do someone of you guys know if some similar script already exists? Or at least some tips on how not to end up writing a 1000 lines script (At this point I would just drop the idea)? All thoughts appreciated. P.S. even an obscure algorithm would probably suffice, 'cause the main problem I'm struggling with is diminishing size perspective calculations |
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