I'm looking for a solution to add a signature to a form. One where someone can sign with their mouse or with their finger on a touch device. I'm wondering if I can use something like jSignature https://willowsystems.github.io/jSignature/#/about/ to create an image, the process the form with php and create a PDF and then add the image to the PDF.
I've researched a bit and haven't found a clear solution for this. Basically I'm wanting to create a simple freelancer website contract that clients would sign online.
I've created a fairly minimum prototype that uses the <canvas>
element to allow signature drawings. This drawing is then added to the form as a base64 url.
Short explanation of the code:
<canvas>
elementmousedown
(pencil down), mousemove
(continue drawing) and mouseup
(pencil up)canvas.toDataUrl()
. This is then set on a hidden input on the form.var canvas = document.getElementById('signature');
var ctx = canvas.getContext("2d");
var drawing = false;
var prevX, prevY;
var currX, currY;
var signature = document.getElementsByName('signature')[0];
canvas.addEventListener("mousemove", draw);
canvas.addEventListener("mouseup", stop);
canvas.addEventListener("mousedown", start);
function start(e) {
drawing = true;
}
function stop() {
drawing = false;
prevX = prevY = null;
signature.value = canvas.toDataURL();
}
function draw(e) {
if (!drawing) {
return;
}
// Test for touchmove event, this requires another property.
var clientX = e.type === 'touchmove' ? e.touches[0].clientX : e.clientX;
var clientY = e.type === 'touchmove' ? e.touches[0].clientY : e.clientY;
currX = clientX - canvas.offsetLeft;
currY = clientY - canvas.offsetTop;
if (!prevX && !prevY) {
prevX = currX;
prevY = currY;
}
ctx.beginPath();
ctx.moveTo(prevX, prevY);
ctx.lineTo(currX, currY);
ctx.strokeStyle = 'black';
ctx.lineWidth = 2;
ctx.stroke();
ctx.closePath();
prevX = currX;
prevY = currY;
}
function onSubmit(e) {
console.log({
'name': document.getElementsByName('name')[0].value,
'signature': signature.value,
});
return false;
}
canvas#signature {
border: 2px solid black;
}
form>* {
margin: 10px;
}
<form action="submit.php" onsubmit="return onSubmit(this)" method="post">
<div>
<input name="name" placeholder="Your name" required />
</div>
<div>
<canvas id="signature" width="300" height="100"></canvas>
</div>
<div>
<input type="hidden" name="signature" />
</div>
<button type="submit">Send</button>
<form>
On the PHP side, you should then be able to decode that base64 string and save it to a file like this:
$img = $_POST['signature'];
$data = base64_decode(preg_replace('#^data:image/\w+;base64,#i', '', $img));
file_put_contents('storage/signature.png', $data);
If you need mobile/touch capability, simply change the events to:
mousemove
: touchmove
mouseup
: touchend
mousedown
: touchstart
If you need both mobile and mouse inputs, you can duplicate the 3 addEventListener
lines so all 6 events are tracked.