JavaScript Canvas to Blob

Usage

Include the (minified) JavaScript Canvas to Blob script in your HTML markup:

<script src="canvas-to-blob.min.js"></script>

The JavaScript Canvas to Blob script is a polyfill for the standard HTML canvas.toBlob method:

var canvas = document.createElement('canvas'); 
/* ... your canvas manipulations ... */
if (canvas.toBlob) {
    canvas.toBlob(
        function (blob) {
            // Do something with the blob object,
            // e.g. creating a multipart form for file uploads:
            var formData = new FormData();
            formData.append('file', blob, fileName);
            /* ... */
        },
        'image/jpeg'
    );
}

Requirements

The JavaScript Canvas to Blob function has zero dependencies.

However, Canvas to Blob is a very suitable complement to the JavaScript Load Image function.

API

In addition to the canvas.toBlob polyfill, the JavaScript Canvas to Blob script provides one additional function called dataURLtoBlob, which is added to the global window object if no AMD loader is used to load the script:

// 80x60px GIF image (color black, base64 data):
var b64Data = 'R0lGODdhUAA8AIABAAAAAP///ywAAAAAUAA8AAACS4SPqcvtD6' +
        'OctNqLs968+w+G4kiW5omm6sq27gvH8kzX9o3n+s73/g8MCofE' +
        'ovGITCqXzKbzCY1Kp9Sq9YrNarfcrvcLDovH5PKsAAA7',
    imageUrl = 'data:image/gif;base64,' + b64Data,
    blob = window.dataURLtoBlob && window.dataURLtoBlob(imageUrl);

License

The JavaScript Canvas to Blob script is released under the MIT license.