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

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

In your application code, use the canvasToBlob() function like this:

var canvas = document.createElement('canvas'); 
/* ... your canvas manipulations ... */
if(!canvasToBlob(
    canvas,
    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);
        /* ... */
    },
    {
        type: fileType,
        name: fileName // Only used by Mozilla Firefox
    }
)) {
    /* ... alternative code for unsupported browsers ... */
};

The JavaScript Canvas to Blob function has zero dependencies.

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

The canvasToBlob() function expects a canvas element as first argument and a callback function as second argument. An options object with the properties name (e.g. "image.png") and image (e.g. "image/png") can be provided as optional third argument.

The function returns true if the browser supports canvas to blob conversion. It calls the provided callback function with the created blob as argument.

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