Can I get image from canvas element and use it in img src tag?

Is there possibility to convert the image present in a canvas element into an image representing by img src?

I need that to crop an image after some transformation and save it. There are a view functions that I found on the internet like: FileReader() or ToBlop(), toDataURL(), getImageData(), but I have no idea how to implement and use them properly in JavaScript.

This is my html:

<img src="http://picture.jpg" id="picture" style="display:none"/>
<tr>
    <td>
        <canvas id="transform_image"></canvas>
    </td>
</tr>
<tr>
    <td>
        <div id="image_for_crop">image from canvas</div>
    </td>
</tr>

In JavaScript it should look something like this:

$(document).ready(function() {
    img = document.getElementById('picture');
    canvas = document.getElementById('transform_image');

    if(!canvas || !canvas.getContext){
        canvas.parentNode.removeChild(canvas);
    } else {
        img.style.position = 'absolute';
    }
    transformImg(90);
    ShowImg(imgFile);
}

function transformImg(degree) {
    if (document.getElementById('transform_image')) {
        var Context = canvas.getContext('2d');
        var cx = 0, cy = 0;
        var picture = $('#picture');
        var displayedImg = {
            width: picture.width(),
            height: picture.height()
        };   
        var cw = displayedImg.width, ch = displayedImg.height
        Context.rotate(degree * Math.PI / 180);
        Context.drawImage(img, cx, cy, cw, ch);
    }
}

function showImg(imgFile) {
    if (!imgFile.type.match(/image.*/))
    return;

    var img = document.createElement("img"); // creat img object
    img.id = "pic"; //I need set some id
    img.src = imgFile; // my picture representing by src
    document.getElementById('image_for_crop').appendChild(img); //my image for crop
}

How can I change the canvas element into an img src image in this script? (There may be some bugs in this script.)

Answers:

Answer

Do this. Add this to the bottom of your doc just before you close the body tag.

<script>
    function canvasToImg() {
      var canvas = document.getElementById("yourCanvasID");
      var ctx=canvas.getContext("2d");
      //draw a red box
      ctx.fillStyle="#FF0000";
      ctx.fillRect(10,10,30,30);

      var url = canvas.toDataURL();

      var newImg = document.createElement("img"); // create img tag
      newImg.src = url;
      document.body.appendChild(newImg); // add to end of your document
    }

    canvasToImg(); //execute the function
</script>

Of course somewhere in your doc you need the canvas tag that it will grab.

<canvas id="yourCanvasID" />
Answer

I´ve found two problems with your Fiddle, one of the problems is first in Zeta´s answer.

the method is not toDataUrl(); is toDataURL(); and you forgot to store the canvas in your variable.

So the Fiddle now works fine http://jsfiddle.net/gfyWK/12/

I hope this helps!

Answer

canvas.toDataURL is not working if the original image URL (either relative or absolute) does not belong to the same domain as the web page. Tested from a bookmarklet and a simple javascript in the web page containing the images. Have a look to David Walsh working example. Put the html and images on your own web server, switch original image to relative or absolute URL, change to an external image URL. Only the first two cases are working.

Answer

Corrected the Fiddle - updated shows the Image duplicated into the Canvas...

And right click can be saved as a .PNG

http://jsfiddle.net/gfyWK/67/

<div style="text-align:center">
<img src="http://imgon.net/di-M7Z9.jpg" id="picture" style="display:none;" />
<br />
<div id="for_jcrop">here the image should apear</div>
<canvas id="rotate" style="border:5px double black; margin-top:5px; "></canvas>
</div>

Plus the JS on the fiddle page...

Cheers Si

Currently looking at saving this to File on the server --- ASP.net C# (.aspx web form page) Any advice would be cool....

Answer

canvas.toDataURL() will provide you a data url which can be used as source:

var image = new Image();
image.id = "pic";
image.src = canvas.toDataURL();
document.getElementById('image_for_crop').appendChild(image);

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