hand_signature 0.6.0

The signature pad widget that allows to draw signature with finger.

A Flutter plugin providing signature pad for drawing smooth signatures. Library is written in pure Dart/Flutter environment to provide support for all platforms..
Easy to use library with variety of draw and export settings.

Signature pad drawing is based on Cubic Bézier curves.

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Usage

    import 'package:hand_signature/signature.dart';

With HandSignatureControl and HandSignaturePainterView is possible to tweak some drawing aspects like stroke width, smoothing ratio or velocity weight.

    final control = HandSignatureControl(
      threshold: 3.0,
      smoothRatio: 0.65,
      velocityRange: 2.0,
    );

    final widget = HandSignaturePainterView(
      control: control,
      color: Colors.blueGrey,
      width: 1.0,
      maxWidth: 10.0,
      type: SignatureDrawType.shape,
    );

HandSignatureControl sets up 'math' to control input touch and handle control points of signature curve.\

• threshold: (LP) controls minimal distance between two points - higher distance creates smoother curve, but less precise. Higher distance also creates input draw lag, because last two points of 'open' curve is not drawn.
• smoothRatio: (0 - 1) controls how smooth curve will be - higher ratio creates smoother curve, but less precise. In most cases best results are with 0.5 - 0.75 ratio.
• velocityRange: (LP/milliseconds) controls curve size based on duration between two points. With higher velocityRange user must swing faster to draw thinner line.

HandSignaturePainterView sets up visual style of signature curve.\

• control: process input and handles math and stores raw data.
• color: line color.
• width: minimal width of line. Width at maximum swing speed (clamped by velocityRange).
• maxWidth: maximum width of line. Width at slowest swing speed.
• type: draw type of curve. Default and main draw type is shape - not so nice as arc, but has better performance. And line is simple path with uniform stroke width.

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Export
Some properties can be modified during export, like canvas size, stroke min/max width and color. There are more ways and more formats how to export signature. Most used are svg and png formats.

    final control = HandSignatureControl();

    final svg = control.toSvg();
    final png = control.toImage();

Parsing
Resulting svg is possible to display in classic flutter_svg widget.
Or use build in HandSignatureView for greater control.

    final widget = HandSignatureView.svg(
      data: svgString,
      strokeWidth: (width) => width * 0.35,
    );

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Contribution
Any contribution is highly welcomed.
Library is in good condition, but still in early development.
Mainly to improve smoothing and line weight to better match real signature.
Remove dependency of flutter_svg and make library dependent only at path_drawing or path_parsing.
Performance can be always better..
Also currently there are no tests or documentation.