contoured_shadow

Soft, shape-following shadows for Flutter — painted from the child's own silhouette rather than a rectangle.

Wrap a cutout image, icon, or any widget with transparency. Opaque pixels cast the shadow; transparent pixels do not. Ideal for product cutouts, badges, and irregular shapes where BoxShadow looks wrong.

Features

• Shadow contour matches the child's alpha / shape
• Configurable blur (isotropic or per-axis), offset, color, opacity, and blend mode
• Toggle shadows with enabled without removing the widget
• Implemented as a lightweight RenderProxyBox (no third-party deps)
• Alias ContouredShadowWidget for drop-in familiarity

Install

dependencies:
  contoured_shadow: ^0.2.0

import 'package:contoured_shadow/contoured_shadow.dart';

Usage

ContouredShadow(
  blurSigma: 8,
  offset: const Offset(0, 6),
  opacity: 0.3,
  child: Image.asset(
    'assets/product_cutout.png',
    width: 180,
  ),
)

The child's opacity and shape define the shadow contour. Fully transparent regions cast no shadow; anti-aliased edges produce a soft matching outline.

Asymmetric blur

blurSigma remains the primary radius for both axes. Set blurSigmaX and/or blurSigmaY to override an axis; any missing axis falls back to blurSigma.

ContouredShadow(
  blurSigma: 6,
  blurSigmaX: 14, // wide horizontal soft edge
  blurSigmaY: 4,  // tighter vertical blur
  offset: const Offset(0, 8),
  child: Icon(Icons.star, size: 64),
)

Disable without removing the wrap

ContouredShadow(
  enabled: showShadow,
  child: myWidget,
)

Customization

Parameter	Default	Description
child	required	Widget whose silhouette becomes the shadow
enabled	true	When false, paints child only (no shadow)
blurSigma	5	Primary Gaussian blur radius (both axes)
blurSigmaX	null	Optional X-axis blur; overrides blurSigma when set
blurSigmaY	null	Optional Y-axis blur; overrides blurSigma when set
offset	Offset(0, 4)	Shadow displacement relative to the child
shadowColor	black	Base shadow color (before opacity)
opacity	0.25	Shadow opacity (0–1)
blendMode	BlendMode.srcIn	Blend mode for the shadow color filter

Example

See the example/ app for icons and shaped surfaces with contoured shadows, including an enabled toggle and asymmetric blur demo.

License

MIT