image to dataUrl

function toDataURL(url) {
    return fetch(url, {
      credentials: 'include',
    })
    .then(response => response.blob())
    .then(blob => new Promise((resolve, reject) => {
        var reader = new FileReader();
        reader.onloadend = () => resolve(reader.result);
        reader.onerror = reject;
        reader.readAsDataURL(blob);
    }));
 }