I am trying to load a bitmap into the canvas following the example here.
Here is my code:
<!DOCTYPE html>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>HTML 5 Reports</title>
<script type="text/javascript">
function draw() {
var ctx = document.getElementById('canvas').getContext('2d');
var img = new Image();
img.onload = function(){
ctx.drawImage(img,0,0);
ctx.beginPath();
ctx.moveTo(30,96);
ctx.lineTo(70,66);
ctx.lineTo(103,76);
ctx.lineTo(170,15);
ctx.stroke(); }
img.src = 'worldmap1.bmp';
}
</script>
</head>
<body onload="draw()">
<canvas id="graph"></canvas>
</body>
</html>
Nothing is drawn in the browser when I view the page. No Errors Given.
Please tell me what I am doing wrong. Thanks!
I guess I should answer this question so I can close it. That is what it seems to say on meta.stackoverflow.com
Ok I forgot the semi-colon after draw(); and canvas id needs to be "canvas" instead of "graph". Solved my own problem =) I feel smart now =) Thanks for the help all. – EddieC 2 mins ago edit.
I have no experience with Canvas, but I would be surprised if BMP files were supported... Try a JPG, PNG or GIF file, those are reliably supported across all browsers.
If its not bitmap related per the other posts... are you sure img.src is a valid path to the file?
Related
This is the first time I use stackoverflow to ask for help, so if there is anything I have done wrong please tell me. And I am not a native English speaker, so hope you understand my problem.
I was intend to create a webpage that can draw lines. There isn't any big issues. However, I realize that each time I use stroke() to draw a new lines, the previous lines become thicker. Can this problem be solved?
<html>
<body>
<div id="coord"></div>
<canvas id="Maintheme" height="800" width="1000"></canvas>
</body>
<script>
var canvas=document.getElementById("Maintheme");
var context=canvas.getContext('2d');
var coordinates;
var Xcoor;
var Ycoor;
var lineboolean=false;
canvas.width=window.innerWidth;
canvas.height=window.innerHeight;
canvas.addEventListener('mousemove',function(evt){
coordinates=evt.clientX+" "+evt.clientY;
Xcoor=evt.clientX;
Ycoor=evt.clientY;
document.getElementById("coord").innerHTML=coordinates;})
canvas.addEventListener('click',function(){
if (lineboolean==false){
context.moveTo(Xcoor,Ycoor);
lineboolean=true;
}
else{
context.lineTo(Xcoor,Ycoor);
context.stroke();
lineboolean=false;
}
})
</script>
</html>
am making a Createjs and html5 project in which I am drawing a shape(Red circle), when I click over the circle it gives alert. It works fine on all desktops and android phones. Except when I open this in a windows phone it works fine on the normal screen but when I zoom the screen it loses it working, an alert is shown when I click anywhere on the screen(maybe where the co-ordinates of the shape resides) but not when I click over the shape(Circle),,
Your help is appreciated
my demo.html
<!DOCTYPE html>
<html>
<head><title></title>
<script type="text/javascript" src="createjs-2013.12.12.min.js"></script>
<script type="text/javascript" src="jquery-1.11.0.min.js"></script>
<script type="text/javascript">
function init() {
var stage = new createjs.Stage("demoCanvas");
var circle = new createjs.Shape();
createjs.Touch.enable(stage);
circle.graphics.beginFill("red").drawCircle(0, 0, 50);
circle.x = 100;
circle.y = 100;
circle.addEventListener("click", function(evt) { /*$("span#log").text(circle.x);*/ alert('clicked'); });
stage.addChild(circle);
stage.update();
}
</script>
</head>
<body onLoad="init();">
<span id="log"></span>
<br>
<canvas id="demoCanvas" width="500" height="300">
alternate content
</canvas>
</body>
</html>..
Here's the project
Not sure if this is relevant as haven't looked at sample code, but I think createjs.Touch.enable works on Stage instances rather than DisplayObjects
See here
I do alot of Research over this topic, and at the end i came to this point that this the
BUG in IE11 . Hope Microsoft helps to solve this.
Im trying to do a composite operation on layers using KineticJS.
Everything works fine in Chrome, but nothing shows for firefox, or IE10
The code runs through without any errors.
You can see the issue here:
http://clients.lilodesign.com/Lilo/Kinetic/
Chrome you should see a circle with a partial bit of the standard MS Blue Trees image showing through. In Firefox and IE10 you just get a blank screen.
You can view the code by viewing the source. Its all in-line and a very simple example to show the issue.
If you remove the following line:
ctx.globalCompositeOperation = "destination-atop";
Then you see the blue trees image with the ellipse on top of it as expected in all three browsers, so the code does "work".
Has anyone else experienced this and found a workaround?
I have searched and tried a couple of suggested solutions such as:
shape intersection with KineticJS
But all these still only seem to work in Chrome.
Any help or pointers would be appreciated.
Thanks
Tyrone.
We used to be able to cheat by grabbing the context of a layer, but now it’s unreliable (as you’ve discovered).
You can still get verrrrry hacky and do it like this: : http://jsfiddle.net/m1erickson/6fTQU/
But don’t ! (Even this hack doesn’t actually work on images with transparent pixels).
Instead, do it the official way by creating a Kinetic custom Shape Object.
Kinetic Shape gives you an official canvas and context to work with.
As a result, the globalCompositeOperation works fine (reliably!).
Here is code and a Fiddle: http://jsfiddle.net/m1erickson/LtxEe/
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>Prototype</title>
<script type="text/javascript" src="http://code.jquery.com/jquery.min.js"></script>
<script src="http://d3lp1msu2r81bx.cloudfront.net/kjs/js/lib/kinetic-v4.5.1.min.js"></script>
<style>
body{ background-color: ivory; }
#container{
border:solid 1px #ccc;
margin-top: 10px;
width:300px;
height:300px;
}
</style>
<script>
$(function(){
var stage = new Kinetic.Stage({
container: 'container',
width: 300,
height: 300
});
var layer = new Kinetic.Layer();
stage.add(layer);
var img=new Image();
img.onload=function(){
buildLayer(img);
}
img.src="https://dl.dropboxusercontent.com/u/139992952/stackoverflow/KoolAidMan.png";
function buildLayer(img){
var myShape=new Kinetic.Shape({
drawFunc:function(canvas){
var ctx=canvas.getContext();
ctx.beginPath();
ctx.drawImage(img,0,0);
ctx.globalCompositeOperation="destination-atop";
ctx.arc(150,150,60,0,Math.PI*2,false);
ctx.closePath();
ctx.fill();
canvas.fillStroke(this);
},
x:0,
y:0,
width:img.width,
height:img.height
});
layer.add(myShape);
layer.draw();
}
}); // end $(function(){});
</script>
</head>
<body>
<div id="container"></div>
</body>
</html>
I tried to create rectangle in canvas, i am bit confused with coordinate system of canvas
<!doctype html>
<html lang="en">
<head>
<meta charset="utf-8" />
<title>jQuery UI Dialog - Modal form</title>
<script src="//ajax.googleapis.com/ajax/libs/jquery/1.8.3/jquery.min.js"></script>
<style>
body{
background-color: #231F20;
}
#ribbonid{
width:90px;
height: 90px;
}
</style>
</head>
<body>
<canvas id='ribbonid' > </canvas>
<script>
$(document).ready(function(){
var $ribbonid = $('#ribbonid');
// get the canvas element using the DOM
var canvas = document.getElementById('ribbonid');
// Make sure we don't execute when canvas isn't supported
if (canvas.getContext){
// use getContext to use the canvas for drawing
var cts = canvas.getContext('2d');
cts.fillStyle = '#f7911e';
cts.beginPath();
cts.moveTo(0, 0);
cts.lineTo(90, 0);
cts.lineTo(90, 90);
cts.lineTo(0, 90);
cts.lineTo(0, 0);
cts.fill();
cts.closePath();
}
});
</script>
</body>
</html>
http://jsfiddle.net/bkf2e/
i am aware of canvas.rect function, but i need to create some different shape for me.
I created rectangle of size (90,90)(square), but it is creating full square.
I know it may be my simple mistake, but can you please help me on that.
you need to set the size of your canvas using the width and height attributes, if you use css to size it then it will scale the default size rather than becoming the size you want, which is why it was distorted like that.
I've updated your jsfiddle with the attributes set and you'll see that it's now square.
solved problem,
it was silly mistake of width and height attribute
<canvas id='ribbonid' width='90' height='90' > </canvas>
I am working through the HTML5 canvas tutorial on the following website:
Mozilla Developers.
In this tutorial, they say that you can use a canvas element as the backdrop of another canvas element. I have tried to do exactly that with the following html page. Unfortunately, the debugger in chrome says failed to load resource. Am I referencing the source canvas object the correct way in the function draw2()?:
<html>
<head>
<title>CANVAS TESTING</title>
<script type="text/javascript">
function draw()
{
var ctx = document.getElementById('tutorial').getContext('2d');
ctx.translate(0,document.getElementById('tutorial').height);
ctx.scale(1,-1)
// Create gradients
var lingrad = ctx.createLinearGradient(0,0,0,150);
lingrad.addColorStop(0, '#fff');
lingrad.addColorStop(0.5, '#66CC00');
lingrad.addColorStop(0.5, '#fff');
lingrad.addColorStop(1, '#00ABEB');
var lingrad2 = ctx.createLinearGradient(0,50,0,95);
lingrad2.addColorStop(0.25, 'rgba(0,0,0,0)');
lingrad2.addColorStop(0.75, '#000');
// assign gradients to fill and stroke styles
ctx.fillStyle = lingrad;
ctx.strokeStyle = lingrad2;
// draw shapes
ctx.fillRect(10,10,130,130);
ctx.strokeRect(50,50,50,50);
}
function draw2()
{
ctx=document.getElementById('canvas').getContext('2d');
img = new Image();
img.onload = function()
{
ctx.drawImage(img,0,0);
}
img.src = document.getElementById('tutorial');
}
</script>
</head>
<body onload="draw()">
<p>This is a test of canvas element.</p>
<canvas id="tutorial" width="400" height="400" style="background-color: black"></canvas>
<br /><br />
<canvas id="canvas" width="400" height="400" style="background-color: black"></canvas>
<p>
<input type="button" onclick="draw2()" value="Draw!" />
</p>
</body>
Your solution is kinda correct but you're making it waaaay more complicated than it has to be.
All you have to do is this, nothing any fancier:
var tut = document.getElementById('tutorial');
ctx.drawImage(tut,0,0); // just put in the canvas you want to draw!
Here's a live jsfiddle example if you need more detail
Ok, I just found the answer to my question.
going off the function in Draw2(), I needed to set my img.src to the following:
img.src = document.getElementById('tutorial').toDataURL();
What this does is returns the base64 encoded data string of the png image of the canvas element.