[Impeller] Implement dithering for gradients #118073
Description
Gradients in Flutter can sometimes experience banding. If we implemented dithering they would look nicer.
I'm not aware of a user directly reporting this issue. Although it takes a person with a bit of graphics savvy to be able to explain the issue. I played around with the LinearGradient widget on a full width 4k display and it was hard for me to get a combination that was noticeable to me on my macbook.
Here is a user that was experiencing banding when using the Paint class: #112498 (comment)
I've personally run into this problem in a game I developed years ago where the designer gave me the parameters and banding appeared.
example
click to maximize the image to see banding better
reproduction code
import 'package:flutter/material.dart';
void main() {
runApp(const MyApp());
}
class MyApp extends StatelessWidget {
const MyApp({super.key});
@override
Widget build(BuildContext context) {
return MaterialApp(
title: 'Flutter Demo',
theme: ThemeData(
primarySwatch: Colors.blue,
),
home: const MyHomePage(title: 'Flutter Demo Home Page'),
);
}
}
class MyHomePage extends StatefulWidget {
const MyHomePage({super.key, required this.title});
final String title;
@override
State<MyHomePage> createState() => _MyHomePageState();
}
class _MyHomePageState extends State<MyHomePage> {
int _counter = 0;
void _incrementCounter() {
setState(() {
_counter++;
});
}
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text(widget.title),
),
body: Center(
child: Container(
width: double.infinity,
decoration: const BoxDecoration(
gradient: LinearGradient(
colors: <Color>[Color(0xffcccccc), Color(0xff333333)])),
child: Column(
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget>[
const Text(
'You have pushed the button this many times:',
),
Text(
'$_counter',
style: Theme.of(context).textTheme.headlineMedium,
),
],
),
),
),
floatingActionButton: FloatingActionButton(
onPressed: _incrementCounter,
tooltip: 'Increment',
child: const Icon(Icons.add),
), // This trailing comma makes auto-formatting nicer for build methods.
);
}
}