function exportToImage() {
    if(activeDocument === null) {
        return null;
    }

    return canvas.toDataURL('image/png');
}

function downloadImage(name, dataUrl) {
    const element = document.createElement('a');

    element.setAttribute('href', dataUrl);
    element.setAttribute('download', name);

    element.style.display = 'none';
    document.body.appendChild(element);

    element.click();
    document.body.removeChild(element);
}

function exportToImageFile() {
    downloadImage('test.png', exportToImage());
}