flutter_svg

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Draw SVG and Android VectorDrawable (XML) files on a Flutter Widget.

Getting Started

This is a Dart-native rendering library. Issues/PRs will be raised in Flutter and flutter/engine as necessary for features that are not good candidates for Dart implementations (especially if they're impossible to implement without engine support). However, not everything that Skia can easily do needs to be done by Skia; for example, the Path parsing logic here isn't much slower than doing it in native, and Skia isn't always doing low level GPU accelerated work where you might think it is (e.g. Dash Paths).

All of the SVGs in the assets/ folder (except the text related one(s)) now have corresponding PNGs in the golden/ folder that were rendered using flutter test tool/gen_golden.dart and compared against their rendering output in Chrome. Automated tests will continue to compare these to ensure code changes do not break known-good renderings.

Basic usage (to create an SVG rendering widget from an asset):

final String assetName = 'assets/image.svg';
final Widget svg = new SvgPicture.asset(
  assetName,
);

You can color/tint the image like so:

final String assetName = 'assets/icon.svg';
final Widget svgIcon = new SvgPicture.asset(
  assetName,
  color: Colors.red,
);

The default placeholder is an empty box (LimitedBox) - although if a height or width is specified on the SvgPicture, a SizedBox will be used instead (which ensures better layout experience). There is currently no way to show an Error visually, however errors will get properly logged to the console in debug mode.

You can also specify a placeholder widget. The placeholder will display during parsing/loading (normally only relevant for network access).

// Will print error messages to the console.
final String assetName = 'assets/image_that_does_not_exist.svg';
final Widget svg = new SvgPicture.asset(
  assetName,
);

final Widget networkSvg = new SvgImage.network(
  'https://site-that-takes-a-while.com/image.svg',
  loadingPlaceholderBuilder: (BuildContext context) => new Container(
      padding: const EdgeInsets.all(30.0),
      child: const CircularProgressIndicator()),
);

If you'd like to render the SVG to some other canvas, you can do something like:

import 'package:flutter_svg/flutter_svg.dart';
final DrawableRoot svgRoot = await svg.loadAsset('assets/image.svg');

// If you only want the final Picture output, just use
final Picture picture = svgRoot.toPicture();

// Otherwise, if you want to draw it to a canvas:
// Optional, but probably normally desirable: scale the canvas dimensions to
// the SVG's viewbox
svgRoot.scaleCanvasToViewBox(canvas);

// Optional, but probably normally desireable: ensure the SVG isn't rendered
// outside of the viewbox bounds
svgRoot.clipCanvasToViewBox(canvas);
svgRoot.draw(canvas, size);

The SvgPicture helps to automate this logic, and it provides some convenience wrappers for getting assets from multiple sources and caching the resultant Picture. It does not render the data to an Image at any point; you certainly can do that in Flutter, but you then lose some of the benefit of having a vector format to begin with.

While I'm making every effort to avoid needlessly changing the API, it's not guarnateed to be stable yet (hence the pre-1.0.0 version). To date, the biggest change is deprecating the SvgImage widgets in favor of SvgPicture - it became very confusing to maintain that name, as Pictures are the underlying mechanism for rendering rather than Images.

See main.dart for a complete sample.

Use Cases

  • Your designer creates a vector asset that you want to include without converting to 5 different raster format resolutions.
  • Your vector drawing is meant to be static and non (or maybe minimally) interactive.
  • You want to load SVGs dynamically from network sources at runtime.
  • You want to paint SVG data and render it to an image.

TODO

This list is not very well ordered. I'm mainly picking up things that seem interesting or useful, or where I've gotten a request to fix something/example of something that's broken.

  • Text support.
  • x Gradient support (Linear: Mostly done, Radial: finishing this will require newer version of flutter).
  • x Dash path support.
  • Dash path with percentage dasharray values.
  • More SVG samples to cover more complicated cases (getting there - please file issues for things that don't work!).
  • Display/visibility support.
  • x Unit tests. In particular, tests that validate XML -> Drawable* structures. (Vastly improved as of 0.2.) this is getting there, just need to stay on top of it.
  • Inheritance of inheritable properties (necessary? preprocess? significant progress, still some rough edges, particularly for definitions).
  • Support for minimal CSS/styles? See also svgcleaner (partial - style attribute mostly supported).
  • XLink/ref support (necessary? partially supported for gradients).
  • Glyph support?
  • Markers.
  • Filters/effects.
  • Android Vector Drawable support (PoC implementation so far).
  • x Caching of image.
  • The XML parsing implementation is heavy for what this really needs. I've made efforts to keep the API forward-reading-only compatible to eventually be able to use a SAX/XMLReader streaming style parser.
  • x Color swapping/hue shifting/tinting of asset.

Probably out of scope

  • SMIL animations. That just seems crazy. I think it'll be possible to animate the SVG but probably in a more Flutter driven way.
  • Full (any?) CSS support - preprocess your SVGs (perhaps with svgcleaner to get rid of all CSS?)
  • Scripting in SVGs
  • Foreign elements
  • Rendering properties/hints

SVG sample attribution

SVGs in /assets/w3samples pulled from W3 sample files

SVGs in /assets/deborah_ufw provided by @deborah-ufw

SVGs in /assets/simple are pulled from trivial examples or generated to test basic functionality - some of them come directly from the SVG 1.1 spec.

SVGs in /assets/wikimedia are pulled from Wikimedia Commons

Android Drawables in assets/android_vd are pulled from Android Documentation and examples.

The Flutter Logo created based on the Flutter Logo Widget © Google.

The Dart logo is from dartlang.org © Google

Please submit SVGs this can't render properly (e.g. that don't render here the way they do in chrome), as long as they're not using anything "probably out of scope" (above).

Libraries

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flutter_svg
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