saving signature

[rajesh-konki18]

Initial commit to save signature

[steveruizok]

Hi Rajesh, thanks for the PR! I'd like to make this one a bit more useful before I merge it in. At the moment it just seems to render the image again in a new navigation page. Is there any way to save or export the image? I'd also be interested in a way to copy out the stroke to SVG—this is something I've implemented in the perfect-freehand demo for web.

[oodavid]

@steveruizok for that you might want to look at some prior-art. The hand_signature plugin has the option to save to png via the canvas, so this is probably a good starting point for this PR.

https://github.com/RomanBase/hand_signature/blob/09166d23195f382c17adc82b0729d5131d249b0e/lib/src/signature_control.dart#L1095

https://github.com/RomanBase/hand_signature/blob/09166d23195f382c17adc82b0729d5131d249b0e/lib/src/signature_control.dart#L1046