I am trying to draw an image on a canvas, in HTML5. For some reason, the image simply isn't drawn onto the canvas, and there are no errors in the console. Here is my code:
<!DOCTYPE html>
<html>
<body>
<img id="image" src="Images/player.png"></img>
<canvas id="canvas" width="1000" height="750"></canvas>
<script>
var canvas = document.getElementById("canvas");
var context = canvas.getContext("2d");
var image = document.getElementById("image");
context.fillStyle = "lightblue";
context.fillRect(0, 0, 1000, 750);
context.drawImage(image, 0, 0);
</script>
</body>
</html>
Can somebody help? Thanks.
You need to add an event listener to the img tag called load. Then in the callback you can call drawImage with the provided img element.
You can do something like this - I have added one stackoverflow image for representation:
const canvas = document.getElementById("canvas");
const context = canvas.getContext("2d");
const image = document.getElementById("image");
context.fillStyle = "lightblue";
context.fillRect(0, 0, 1000, 750);
image.addEventListener('load', e => context.drawImage(image, 0, 0));
<img id="image" src="https://stackoverflow.blog/wp-content/themes/stackoverflow-oct-19/images2/header-podcast.svg" height="100px"></img>
<canvas id="canvas" width="1000" height="750"></canvas>
From the documentation: Drawing an image to the canvas
I hope this helps!
Related
I am trying to add a circle over the image and I am using the .onload function too but the circle is still being drawn below the image.
<!DOCTYPE html>
<html>
<body>
<canvas id="myCanvas" width="1024" height="500" style="border:1px solid #d3d3d3;">
Your browser does not support the canvas element.
</canvas>
<script>
var canvas = document.getElementById("myCanvas");
var background = new Image();
background.src = "https://i.imgur.com/ua7gL3M.png";
// Make sure the image is loaded first otherwise nothing will draw.
background.onload = function(){
ctx.drawImage(background,0,0);
}
var ctx = canvas.getContext("2d");
ctx.beginPath();
ctx.arc(512,200,60,0,2*Math.PI);
ctx.strokeStyle = "red"
ctx.lineWidth = 5;
ctx.stroke();
</script>
</body>
</html>
When I run the code snippet, there's a brief moment the circle is visible before the image is rendered. The image has to wait to load before it is rendered, but the circle is being drawn immediately. Because of that, the circle is drawn first then the image is placed on top of it. To fix this, you can draw the circle after the image is rendered. See this revised code snippet:
<!DOCTYPE html>
<html>
<body>
<canvas id="myCanvas" width="1024" height="500" style="border:1px solid #d3d3d3;">
Your browser does not support the canvas element.
</canvas>
<script>
var canvas = document.getElementById("myCanvas");
var background = new Image();
background.src = "https://i.imgur.com/ua7gL3M.png";
// Make sure the image is loaded first otherwise nothing will draw.
background.onload = function(){
ctx.drawImage(background,0,0);
// The following lines were moved into the onload callback
ctx.beginPath();
ctx.arc(512,200,60,0,2*Math.PI);
ctx.strokeStyle = "red"
ctx.lineWidth = 5;
ctx.stroke();
}
var ctx = canvas.getContext("2d");
</script>
</body>
</html>
I'm trying to load the image on canvas but it's not working:(
I checked functions and variables much time but I couldn't find any errors.
Help me to find the reasons why it can't be loaded.
When I run it on the tomcat server, only the canvas with aliceblue color is shown.
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Print image and text</title>
<script>
function drawPicture(ctx) {
var img = new Image();
img.addEventListener('load', function() {
ctx.drawImage(img, 20, 20, 100, 100);
ctx.font = "50px forte";
ctx.strokeStyle="blue";
ctx.fillStyle = "violet";
ctx.strokeText("Spongebob", 20, 100);
ctx.fillText("Spongebob", 20, 100);
}, false);
img.src = "spongebob.png";
}
</script>
</head>
<body>
<h3>Print image and text</h3>
<hr>
<canvas id="myCanvas" width="300" height="130"
style="background-color:aliceblue"></canvas>
<script>
var canvas = document.getElementById("myCanvas");
var context = canvas.getContext("2d");
drawPicture(context);
</script>
</body>
</html>
Your code is fine, here is an example with a different image...
<!DOCTYPE html>
<html>
<body>
<canvas id="myCanvas" width="300" height="130"></canvas>
<script>
function drawPicture(ctx) {
var img = new Image();
img.addEventListener('load', function() {
ctx.drawImage(img, 20, 20, 100, 100);
ctx.font = "50px forte";
ctx.strokeStyle = "blue";
ctx.fillStyle = "violet";
ctx.strokeText("Spongebob", 20, 100);
ctx.fillText("Spongebob", 20, 100);
}, false);
img.src = "http://i.stack.imgur.com/UFBxY.png";
}
var canvas = document.getElementById("myCanvas");
var context = canvas.getContext("2d");
drawPicture(context);
</script>
</body>
</html>
Only thing could be that the image you are trying to load does not exist...
As #Kaiido mentioned in the comments you need to debug this, check in your browser developer tools see if the image is loading correctly.
You should see something like:
instead of image.addEventListener, try doing image.onload?
You can instead of using the load event in the image, try adding the image directly on the canvas.
function drawPicture(ctx) {
var img = new Image();
img.src = "spongebob.png";
ctx.drawImage(img, 20, 20, 100, 100);
ctx.font = "50px forte";
ctx.strokeStyle="blue";
ctx.fillStyle = "violet";
ctx.strokeText("Spongebob", 20, 100);
ctx.fillText("Spongebob", 20, 100);
}
var canvas = document.getElementById("myCanvas");
var context = canvas.getContext("2d");
drawPicture(context);
<h3>Print image and text</h3>
<hr>
<canvas id="myCanvas" width="300" height="130"
style="background-color:aliceblue"></canvas>
I am trying to load an image of me on my html canvas.....
The image is in the right folder...... I just get a weird error (as shown above) im not sure what is going on if you know please let me know.
Here is the code:
<!DOCTYPE html>
<html>
<body>
<canvas id="myCanvas" width="800" height="500"></canvas>
<script>
var canvas = document.getElementById("myCanvas");
var ctx = canvas.getContext("2d");
ctx.fillStyle = "black";
ctx.fillRect(0,0,800,500)
var img = new Image();
img.src = "science.PNG";
img.onload = function() {
context.drawImage(img, 145, 145);
};
</script>
</body>
</html>
context.drawImage(img, 145, 145);
Try changing 'context' to 'ctx'.
hi i am trying to draw image with a button in canvas. But i can not draw in the clear canvas. so;
<!doctype html>
<html>
<head>
<meta charset="utf-8">
<title>Başlıksız Belge</title>
</head>
<body>
<input type="button" id="b1" value="ciz">
<canvas id="canvas" height="300" width="600" style="border: solid;background-color: brown; " >Eski Sürüm Tarayıcı . </canvas>
<script>
var canvas = document.getElementById('canvas');
var ctx = canvas.getContext('2d');
var b1 =document.getElementById("b1");
var image = new Image(60, 45); // using optional size for image
var kontrol;
image.src = '/pika.png'; //it is in my pc
image.onload = function(){ // i don't want draw the image on load
kontrol=true;}
b1.onclick=function(){ // i want draw with button
if(kontrol=true){
ctx.drawImage(image, 0, 0);
}
}
</script>
</body>
</html>
when i try with image on load function it is working but i want draw with the button
No problem i get it. thanks...
var canvas = document.getElementById('canvas');
var ctx = canvas.getContext('2d');
var b1 =document.getElementById("b1");
var image = new Image(60, 45);
b1.onclick=function(){
image.src = 'https://i.hizliresim.com/nWdGrR.png';
image.onload = function(){
ctx.drawImage(image, 0, 0);
}
}
If pika.png is located in same directory as your html file then just remove the forward slash before your image's name: image.src = 'pika.png';
I want to draw an image on canvas using JS.
This is my html code:
<canvas style="width:1000px;height:600px;border:1px solid black;" id="canvas"> </canvas>
This is my js code:
var canvas = document.getElementById('canvas');
var ctx = canvas.getContext('2d');
var img = new Image();
img.onload = function(){
ctx.drawImage(img, 0, 0,1000,600)
}
img.src = someUrlToJpgImage;
This is the origin jpg image (1000x600) which is located on server:
This is the result (1000x600) I see in browser:
As you see this is scaled the top left corner of the image but not the whole image as expected. I tried to add to js code:
ctx.imageSmoothingEnabled = false;
ctx.webkitImageSmoothingEnabled = false;
ctx.mozImageSmoothingEnabled = false;
but it didn't help.
How to solve this problem?
You should set the amount of pixels desired on the canvas element:
<canvas style="width:1000px;height:600px;border:1px solid black;" height="600" width="1000" id="canvas"> </canvas>