How to Convert an HTML Element to a Canvas Element

How can I convert an HTML element to a canvas element?

Sorry, the browser won't render HTML into a canvas.

It would be a potential security risk if you could, as HTML can include content (in particular images and iframes) from third-party sites. If canvas could turn HTML content into an image and then you read the image data, you could potentially extract privileged content from other sites.

To get a canvas from HTML, you'd have to basically write your own HTML renderer from scratch using drawImage and fillText, which is a potentially huge task. There's one such attempt here but it's a bit dodgy and a long way from complete. (It even attempts to parse the HTML/CSS from scratch, which I think is crazy! It'd be easier to start from a real DOM node with styles applied, and read the styling using getComputedStyle and relative positions of parts of it using offsetTop et al.)

Rendering HTML elements to canvas

You won't get real HTML rendering to <canvas> per se currently, because canvas context does not have functions to render HTML elements.

There are some emulations:

html2canvas project http://html2canvas.hertzen.com/index.html (basically a HTML renderer attempt built on Javascript + canvas)

HTML to SVG to <canvas> might be possible depending on your use case:

https://github.com/miohtama/Krusovice/blob/master/src/tools/html2svg2canvas.js

Also if you are using Firefox you can hack some extended permissions and then render a DOM window to <canvas>

https://developer.mozilla.org/en-US/docs/HTML/Canvas/Drawing_Graphics_with_Canvas?redirectlocale=en-US&redirectslug=Drawing_Graphics_with_Canvas#Rendering_Web_Content_Into_A_Canvas

Convert HTML To Canvas

As I stated earlier, html2canvas will do this. A minimal example. Updated fiddle

html2canvas($('#MyHTMLCODE'), {    onrendered: function(canvas) {        $('#canvas').replaceWith(canvas);    },    //width: 200,    //height: 200});

.container {    width: 500px;    max-height: 500px;    margin: 10px;    border: 1px solid #fff;    background-color: #ffffff;    box-shadow: 0px 2px 7px #292929;    -moz-box-shadow: 0px 2px 7px #292929;    -webkit-box-shadow: 0px 2px 7px #292929;    border-radius: 10px;    -moz-border-radius: 10px;    -webkit-border-radius: 10px;}.mainbody,.header,.footer {    padding: 5px;}.mainbody {    margin-top: 0;    min-height: 150px;    max-height: 388px;    overflow: auto;}.header {    height: 40px;    border-bottom: 1px solid #EEE;    background-color: #ff8080;    height: 40px;    -webkit-border-top-left-radius: 5px;    -webkit-border-top-right-radius: 5px;    -moz-border-radius-topleft: 5px;    -moz-border-radius-topright: 5px;    border-top-left-radius: 5px;    border-top-right-radius: 5px;}.footer {    height: 40px;    background-color: #b3c6ff;    border-top: 1px solid #DDD;    -webkit-border-bottom-left-radius: 5px;    -webkit-border-bottom-right-radius: 5px;    -moz-border-radius-bottomleft: 5px;    -moz-border-radius-bottomright: 5px;    border-bottom-left-radius: 5px;    border-bottom-right-radius: 5px;}
section {    width: 80%;    height: 200px;       margin: auto;    padding: 10px;}div#one {    width: 15%;    height: 200px;    background: #99ffbb;    float: left;}div#two {    margin-left: 15%;    height: 200px;    background: #ffcccc;}

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.0.2/jquery.min.js"></script><script src="https://cdnjs.cloudflare.com/ajax/libs/html2canvas/0.4.1/html2canvas.js"></script><b>My HTML Code</b><br><div id="MyHTMLCODE"><div class="container">    <div class="header">        Header    </div>    <div class="mainbody">    My Main Body       <section>    <div id="one"> <b>First</b> </div>    <div id="two"> <b>Second</b> </div></section>    </div>    <div class="footer">        Footer    </div></div></div>

<br><b> My Convert Canvas</b><br><canvas id="canvas" style="border:2px solid black;" width="200" height="200"></canvas>

Convert html img element to canvas

You're not using drawImage correctly. See here: https://developer.mozilla.org/en-US/docs/Web/API/CanvasRenderingContext2D/drawImage

The third example allows you to specify x,y,width and height parameter of both source and destination: ctx.drawImage(image, sx, sy, sWidth, sHeight, dx, dy, dWidth, dHeight);

So the easiest fix in your case would be something like:

context.drawImage(myImgElement, 0, 0, 1600, 900, 0, 0, 796, 448);

And here it is in action (go Full Page because of the size):

function convertImgToCanvas(){
    var myImgElement = document.getElementById("myImg");
    var myCanvasElement = document.createElement("canvas");
    // don't forget to add it to the DOM!!
    document.body.appendChild(myCanvasElement); 
    myCanvasElement.width = 796;
    myCanvasElement.height = 448;
    var context = myCanvasElement.getContext('2d');
    context.drawImage(myImgElement, 0, 0, 1600, 900, 0, 0, 796, 448);
    // remove the image for the snippet
    myImgElement.style.display = 'none';
}

convertImgToCanvas();

<div class="span12">
    <img id="myImg" src="https://via.placeholder.com/1600x900" style="max-width: 100%; height: auto;" />
</div>

Render HTML to an image

There is a lot of options and they all have their pro and cons.

Option 1: Use an API

ApiFlash (based on chrome)
EvoPDF (has an option for html)
Grabzit
HTML/CSS to Image API
...

Pros

Execute Javascript
Near perfect rendering
Fast when caching options are correctly used
Scale is handled by the APIs
Precise timing, viewport, ...
Most of the time they offer a free plan

Cons

Not free if you plan to use them a lot

Option 2: Use one of the many available libraries

dom-to-image
wkhtmltoimage (included in the wkhtmltopdf tool)
IMGKit (for ruby and based on wkhtmltoimage)
imgkit (for python and based on wkhtmltoimage)
python-webkit2png
...

Pros

Conversion is quite fast most of the time

Cons

Bad rendering
Does not execute javascript
No support for recent web features (FlexBox, Advanced Selectors, Webfonts, Box Sizing, Media Queries, ...)
Sometimes not so easy to install
Complicated to scale

Option 3: Use PhantomJs and maybe a wrapper library

PhantomJs
node-webshot (javascript wrapper library for PhantomJs)
...

Pros

Execute Javascript
Quite fast

Cons

Bad rendering
No support for recent web features (FlexBox, Advanced Selectors, Webfonts, Box Sizing, Media Queries, ...)
Complicated to scale
Not so easy to make it work if there is images to be loaded ...

Option 4: Use Chrome Headless and maybe a wrapper library

Chrome Headless
chrome-devtools-protocol
Puppeteer (javascript wrapper library for Chrome headless)
...

Pros

Execute Javascript
Near perfect rendering

Cons

Not so easy to have exactly the wanted result regarding:
- page load timing
- viewport dimensions
Complicated to scale
Quite slow and even slower if the html contains external links

Disclosure: I'm the founder of ApiFlash. I did my best to provide an honest and useful answer.

Convert a Canvas element into Image element

Loading an Image can take some time. In your code, toDataURL is returned before image is loaded and painted on canvas.

To resolve this, you can use Promise to wait until the image is loaded and then get the URL of the canvas.

function generateImage() {
  const promise = new Promise((resolve, reject) => {
    let event_date = "11-02-2022";
    let event_name = "Prom Night";

    let canvas = document.getElementById("your-canvas");
    let ctx = canvas.getContext("2d");

    ctx.font = "26px Arial";
    ctx.textAlign = "center";

    // For Heading
    ctx.fillText(event_date + " - " + event_name, 400, 50);

    var img = new Image();
    img.setAttribute("crossorigin", "anonymous");
    img.src = "https://picsum.photos/200/300";
    img.onload = () => {
      ctx.drawImage(img, 100, 100);
      resolve(canvas.toDataURL("image/jpg"));
    };
  });
  return promise;
}

generateImage().then((value) => {
  $("#gen-image").attr("src", value);
});

<script src="https://code.jquery.com/jquery-3.6.0.js" integrity="sha256-H+K7U5CnXl1h5ywQfKtSj8PCmoN9aaq30gDh27Xc0jk=" crossorigin="anonymous"></script>

<center>
  <h1>CANVAS ELEMENT</h1>
</center>
<br>
<canvas id="your-canvas" width="1000" height="400"></canvas>
<center>
  <h1>IMAGE ELEMENT</h1>
</center>
<br>
<img src="" id="gen-image" alt="Sample Image" style="border: 0.1em solid black;">

How can I convert an HTML element to a canvas element?

Sorry, the browser won't render HTML into a canvas.

How to Convert an HTML Element to a Canvas Element

How can I convert an HTML element to a canvas element?

Rendering HTML elements to canvas

Convert HTML To Canvas

Convert html img element to canvas

Render HTML to an image

Option 1: Use an API

Option 2: Use one of the many available libraries

Option 3: Use PhantomJs and maybe a wrapper library

Option 4: Use Chrome Headless and maybe a wrapper library

Convert a Canvas element into Image element

How can I convert an HTML element to a canvas element?

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