secure_watermark

A Flutter package to render a visible watermark overlay over protected content. Part of the FlutterPlaza Security Suite.

Watermarks deter screenshots and make leaks traceable by tiling user-identifying text (user ID, email, timestamp) across the entire widget area. The overlay is rendered with CustomPainter — no native code required.

Features

• Diagonal tiled text overlay with configurable opacity, rotation, font size, and spacing
• Staggered brick pattern (alternate rows offset) for crop resistance
• IgnorePointer — watermark does not intercept touch events
• RepaintBoundary — watermark repaints are isolated from child content
• enabled flag to toggle visibility without removing from widget tree
• Pure Flutter — works on all platforms (no plugin, no method channels)

Installation

dependencies:
  secure_watermark: ^0.1.0

Usage

import 'package:secure_watermark/secure_watermark.dart';

Watermark(
  text: 'user@example.com  2026-02-15',
  style: const WatermarkStyle(opacity: 0.2, rotate: -45),
  enabled: true,
  child: MyProtectedContent(),
)

Toggle watermark at runtime

Watermark(
  text: 'user@example.com',
  enabled: isWatermarkVisible, // controlled by setState, provider, etc.
  child: MyProtectedContent(),
)

Customize style

const style = WatermarkStyle(
  opacity: 0.2,        // 0.0–1.0 (default: 0.15)
  rotate: -45,         // degrees (default: -30)
  fontSize: 14,        // logical pixels (default: 16)
  rowSpacing: 60,      // vertical gap between rows (default: 80)
  columnSpacing: 100,  // horizontal gap between columns (default: 120)
  fontWeight: FontWeight.bold,
  staggered: true,     // brick pattern offset (default: true)
);

API Reference

Watermark

Property	Type	Default	Description
text	String	required	Text to tile as the watermark
style	WatermarkStyle	WatermarkStyle()	Visual configuration
enabled	bool	true	Whether the overlay is visible
child	Widget	required	Content to display beneath the watermark

WatermarkStyle

Property	Type	Default	Description
opacity	double	0.15	Text opacity (0.0–1.0)
rotate	double	-30	Rotation angle in degrees
textColor	Color	Color(0xFF9E9E9E)	Text color (opacity applied separately)
fontSize	double	16	Font size in logical pixels
rowSpacing	double	80	Vertical spacing between rows
columnSpacing	double	120	Horizontal spacing between columns
fontWeight	FontWeight	FontWeight.normal	Font weight
staggered	bool	true	Offset alternate rows for brick pattern

How it works

The Watermark widget uses a Stack to layer a CustomPaint overlay on top of the child content. The WatermarkPainter:

1. Builds a ui.Paragraph with the watermark text
2. Translates and rotates the canvas around its center
3. Tiles the paragraph in a grid covering the full diagonal extent (ensuring no gaps after rotation)
4. In staggered mode, offsets alternate rows by half the column spacing — creating a brick pattern that is harder to crop out

The overlay is wrapped in IgnorePointer (touches pass through) and RepaintBoundary (repaints are isolated from the child).

Related packages

• no_screenshot — Screenshot & recording prevention
• no_tapjack — Tapjacking & overlay attack detection

License

BSD 3-Clause License. See LICENSE for details.