I currently have this code that I got on this site, but I would like to add a watermark when exporting the graphic to PDF, any help is welcome.
<head>
<script src="https://www.gstatic.com/charts/loader.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/jspdf/1.3.5/jspdf.min.js"></script>
<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/css/bootstrap.min.css">
<link rel="stylesheet" href="font/css/font-awesome.min.css">
<script>
google.charts.load('current', {
packages: ['controls', 'corechart', 'table']
}).then(function () {
var data = new google.visualization.DataTable();
data.addColumn('number', 'X');
data.addColumn('number', 'y0');
data.addRows([
[0, 0], [1, 10], [2, 23], [3, 17], [4, 18], [5, 9],
[6, 11], [7, 27], [8, 33], [9, 40], [10, 32], [11, 35],
[12, 30], [13, 40], [14, 42], [15, 47], [16, 44], [17, 48],
[18, 52], [19, 54], [20, 42], [21, 55], [22, 56], [23, 57],
[24, 60], [25, 50], [26, 52], [27, 51], [28, 49], [29, 53],
[30, 55], [31, 60], [32, 61], [33, 59], [34, 62], [35, 65],
[36, 62], [37, 58], [38, 55], [39, 61], [40, 64], [41, 65],
[42, 63], [43, 66], [44, 67], [45, 69], [46, 69], [47, 70],
[48, 72], [49, 68], [50, 66], [51, 65], [52, 67], [53, 70],
[54, 71], [55, 72], [56, 73], [57, 75], [58, 70], [59, 68],
[60, 64], [61, 60], [62, 65], [63, 67], [64, 68], [65, 69],
[66, 70], [67, 72], [68, 75], [69, 80]
]);
var container = document.getElementById('chart_div');
var chart = new google.visualization.LineChart(container);
var btnSave = document.getElementById('save-pdf');
google.visualization.events.addListener(chart, 'ready', function () {
btnSave.disabled = false;
});
btnSave.addEventListener('click', function () {
var doc = new jsPDF();
doc.addImage(chart.getImageURI(), 0, 0);
doc.save('chart.pdf');
}, false);
chart.draw(data, {
chartArea: {
bottom: 24,
left: 36,
right: 12,
top: 48,
width: '100%',
height: '100%'
},
height: 600,
title: 'Prueba de Luis Serrano para expoartar a PDF',
width: 600
});
});
</script>
</head>
<body>
<input id="save-pdf" class="fa fa-file-pdf-o" type="button" value="Exportar a PDF" disabled /><br>
<i aria-hidden="true"></i>
<div id="chart_div"></div>
<body>