Not using this really clever bit

canvas-to-image.js

function () {
    actions.zoomForPrint();
    window.requestAnimationFrame(function () {
        const imgData = getImageFromCanvas();
        // atob to base64_decode the data-URI
        const imgSrc = atob(imgData.split(",")[1]);
        // Use typed arrays to convert the binary data to a Blob
        const buffer = new ArrayBuffer(imgSrc.length);
        var view = new Uint8Array(buffer);
        for (var i = 0; i < imgSrc.length; i++) {
            view[i] = imgSrc.charCodeAt(i) & 0xff;
        }
        var blob = new Blob([buffer], { type: "application/octet-stream" });
        // Use the URL object to create a temporary URL
        var url = window.URL.createObjectURL(blob);
        // Download
        location.href = url;
    });
}