Cannot clear signature if bgColour = 'transparent'

[dancrew32]

1.) setup demo (google chrome, latest)
2.) var pad = $('.sigPad').signaturePad({ bgColour: 'transparent' });
3.) draw signature
4.) pad.clearCanvas()
5.) observe how signature remains (expected: signature cleared)

The signature clears just fine if bgColour is is '#fff' or any other hex value. Would love for it to work with transparency so that you can style custom backgrounds.

[dancrew32]

wondering if there is some easy method to destroy the signature before you clear the canvas here: https://github.com/thomasjbradley/signature-pad/blob/master/jquery.signaturepad.js#L243