37

I have converted the source content from the <img> html tag to a base64String using JavaScript. The image was displayed clearly. Now I want to save that image to user's disk using javascript.

<html>
    <head>
    <script>
        function saveImageAs () {
            var imgOrURL;
            embedImage.src = "data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAUA" +
                             "AAAFCAYAAACNbyblAAAAHElEQVQI12P4//8/w38GIAXDIBKE0DHxgljNBAAO" +
                             "9TXL0Y4OHwAAAABJRU5ErkJggg==";
            imgOrURL = embedImage;
            if (typeof imgOrURL == 'object')
                imgOrURL = embedImage.src;
            window.win = open(imgOrURL);
            setTimeout('win.document.execCommand("SaveAs")', 0);
        }
    </script>
    </head>
    <body>
        <a href="#" ONCLICK="saveImageAs(); return false" >save image</a>

        <img id="embedImage" alt="Red dot">
    </body>
</html>

This code worked well when I set the image path as source for <img> html tag. However, when I pass the source as base64String does not work.

How to achieve what I want?

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3
  • I know there are limits about usage of data:image in IE... file size and other. Try to look on it before. Commented Oct 31, 2011 at 8:45
  • if it has limits ,then it should not have been appeared in the screen. but the image is displayed even for long sized images . i couldn't be able to save that image tom disk . Commented Oct 31, 2011 at 8:58
  • can i pass bytearray as source for <img> tag using javascript? Commented Oct 31, 2011 at 9:41

4 Answers 4

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54

HTML5 download attribute

Just to allow user to download the image or other file you may use the HTML5 download attribute.

Static file download

<a href="/images/image-name.jpg" download>
<!-- OR -->
<a href="/images/image-name.jpg" download="new-image-name.jpg">

Dynamic file download

In cases requesting image dynamically it is possible to emulate such download.

If your image is already loaded and you have the base64 source then:

function saveBase64AsFile(base64, fileName) {
    var link = document.createElement("a");

    document.body.appendChild(link); // for Firefox

    link.setAttribute("href", base64);
    link.setAttribute("download", fileName);
    link.click();
}

Otherwise if image file is downloaded as Blob you can use FileReader to convert it to Base64:

function saveBlobAsFile(blob, fileName) {
    var reader = new FileReader();

    reader.onloadend = function () {    
        var base64 = reader.result ;
        var link = document.createElement("a");

        document.body.appendChild(link); // for Firefox

        link.setAttribute("href", base64);
        link.setAttribute("download", fileName);
        link.click();
    };

    reader.readAsDataURL(blob);
}

Firefox

The anchor tag you are creating also needs to be added to the DOM in Firefox, in order to be recognized for click events (Link).

IE is not supported: Caniuse link

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3 Comments

Now Safari is supported.
For me, it worked on Chrome, but it did not work on Firefox. Does anyone face the same problem?
On Firefox, the anchor tag must be added to DOM in order to click event work. See stackoverflow.com/q/48642223/1882644
25

In JavaScript you cannot have the direct access to the filesystem. However, you can make browser to pop up a dialog window allowing the user to pick the save location. In order to do this, use the replace method with your Base64String and replace "image/png" with "image/octet-stream":

"data:image/png;base64,iVBORw0KG...".replace("image/png", "image/octet-stream");

Also, W3C-compliant browsers provide 2 methods to work with base64-encoded and binary data:

Probably, you will find them useful in a way...

Here is a refactored version of what I understand you need:

window.addEventListener('DOMContentLoaded', () => {
  const img = document.getElementById('embedImage');
  img.src = 'data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAUA' +
    'AAAFCAYAAACNbyblAAAAHElEQVQI12P4//8/w38GIAXDIBKE0DHxgljNBAAO' +
    '9TXL0Y4OHwAAAABJRU5ErkJggg==';

  img.addEventListener('load', () => button.removeAttribute('disabled'));
  
  const button = document.getElementById('saveImage');
  button.addEventListener('click', () => {
    window.location.href = img.src.replace('image/png', 'image/octet-stream');
  });
});
<!DOCTYPE html>
<html>

<body>
  <img id="embedImage" alt="Red dot" />
  <button id="saveImage" disabled="disabled">save image</button>
</body>

</html>

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16 Comments

Note that atob and btoa have never been part of any standard. They are supported by some standards-compliant browsers, but don't count on it being in all of them.
@AndyE Correct. That's why you have to perform feature testing before using these methods.
@vengatesh : please see the updated answer. keep in mind that you'll have to specify the correct file extension in order to have your image saved properly.
@John Doe:thanks alot . but it doesn't work with IE ,can we get the file location from from user? can we have the same file format as before?. because all are saved as .part file.
jsfiddle is dead :(
|
3

This Works

function saveBase64AsFile(base64, fileName) {
    var link = document.createElement("a");
    document.body.appendChild(link);
    link.setAttribute("type", "hidden");
    link.href = "data:text/plain;base64," + base64;
    link.download = fileName;
    link.click();  
    document.body.removeChild(link);
}

Based on the answer above but with some changes

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Comments

0

Check out https://github.com/eligrey/FileSaver.js/ which wraps the HTML5 method and provides workarounds for e.g. IE10.

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