4Q-s-r-o/signature

signature

pub package

A Flutter plugin providing performance optimized signature canvas with ability to set custom style, boundaries and initial state. This is native flutter implementation, so it supports all platforms.

Why

In time of creation of this plugin, there was no available solution that had:

• required performance on wide range of devices
• ability to set canvas boundaries
• ability to initialize using previously saved state

Migration to 5.0.0+

• This version no longer wraps Signature in Expanded widget if you are using it without specifying dimensions
• This removes error Incorrect use of ParentDataWidget, see this issue for more information.
• If you are passing dimensions to widget, you do not have to change anything.
• If you are using widget without dimensions inside Row, Column or Flex widgets, you have to wrap Signature inside Expanded yourself.
• If you are using widget without dimensions, but not inside mentioned widgets you do not have change anything and error should dissapear from your logs :)

Usage

To use this plugin, add signature as a dependency in your pubspec.yaml file.

Example

Take a look at our example project as well: Signature Demo

// IMPORT PACKAGE
import 'package:signature/signature.dart';

// Initialise a controller. It will contains signature points, stroke width and pen color.
// It will allow you to interact with the widget
final SignatureController _controller = SignatureController(
    penStrokeWidth: 5,
    penColor: Colors.red,
    exportBackgroundColor: Colors.blue,
);

// INITIALIZE. RESULT IS A WIDGET, SO IT CAN BE DIRECTLY USED IN BUILD METHOD 
var _signatureCanvas = Signature(
  controller: _controller,
  width: 300,
  height: 300,
  backgroundColor: Colors.lightBlueAccent,
);

// CLEAR CANVAS
_controller.clear();

// EXPORT BYTES AS PNG
// The exported image will be limited to the drawn area
_controller.toPngBytes();

// isEmpty/isNotEmpty CAN BE USED TO CHECK IF SIGNATURE HAS BEEN PROVIDED
_controller.isNotEmpty; //true if signature has been provided
_controller.isEmpty; //true if signature has NOT been provided

// EXPORT POINTS (2D POINTS ROUGHLY REPRESENTING WHAT IS VISIBLE ON CANVAS)
var exportedPoints = _controller.points;

//EXPORTED POINTS CAN BE USED TO INITIALIZE PREVIOUS CONTROLLER
final SignatureController _controller = SignatureController(points: exportedPoints);

//DONT FORGET TO DISPOSE IT IN THE `dispose()` METHOD OF STATEFUL WIDGETS
@override
void dispose() {
  _controller.dispose();
  super.dispose();
}

Example image

Contribution and Support

• See Contribution guide for more info