Color.withValues(alpha: x) expects values between 0...1 instead of 0...255 #160592
Description
Steps to reproduce
- Run the provided sample on iOS 18.1
- Observe that colors are fully opaque if alpha is bigger than 1 when created with
Color.withValues(alpha: 1.01)
My expectation would be that the documentation of Color class is correct -- you should be able to provide alpha with values between 0 and 255 or the docs for withValues should be more explicit about accepted values of alpha.
/// The alpha channel of this color in an 8 bit value.
///
/// A value of 0 means this color is fully transparent. A value of 255 means
/// this color is fully opaque.
@Deprecated('Use .a.')
int get alpha => (0xff000000 & value) >> 24;
/// The alpha channel of this color as a double.
///
/// A value of 0.0 means this color is fully transparent. A value of 1.0 means
/// this color is fully opaque.
@Deprecated('Use .a.')
double get opacity => alpha / 0xFF;Expected results
Alpha values between 0 and 255 should result with semi-opaque colors
Actual results
Alpha of 1 or more is fully opaque
Code sample
Code sample
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(
colorScheme: ColorScheme.fromSeed(seedColor: Colors.deepPurple),
useMaterial3: true,
),
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> {
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
backgroundColor: Theme.of(context).colorScheme.inversePrimary,
title: Text(widget.title),
),
body: Center(
child: Column(
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget>[
for (var i = 0; i < 10; i++)
Container(
color: Color(0xFF000000).withValues(alpha: 255.0 * i / 10),
width: 200,
height: 20,
child: Text(
'$i, alpha:${255.0 * i / 10}',
style: TextStyle(color: Colors.red),
),
)
],
),
),
);
}
}
Screenshots or Video
Screenshots / Video demonstration
| Current behavior | Expected behavior |
|---|---|
 |
 |
Logs
Logs
Not needed
Flutter Doctor output
Doctor output
[✓] Flutter (Channel stable, 3.27.1, on macOS 15.1.1 24B91 darwin-arm64, locale pl-PL)
• Flutter version 3.27.1 on channel stable at /Users/dominik/fvm/versions/stable
• Upstream repository https://github.com/flutter/flutter.git
• Framework revision 17025dd882 (3 days ago), 2024-12-17 03:23:09 +0900
• Engine revision cb4b5fff73
• Dart version 3.6.0
• DevTools version 2.40.2
[!] Android toolchain - develop for Android devices (Android SDK version 34.0.0)
• Android SDK at /Users/dominik/Library/Android/sdk
✗ cmdline-tools component is missing
Run `path/to/sdkmanager --install "cmdline-tools;latest"`
See https://developer.android.com/studio/command-line for more details.
✗ Android license status unknown.
Run `flutter doctor --android-licenses` to accept the SDK licenses.
See https://flutter.dev/to/macos-android-setup for more details.
[✓] Xcode - develop for iOS and macOS (Xcode 16.2)
• Xcode at /Applications/Xcode.app/Contents/Developer
• Build 16C5032a
• CocoaPods version 1.16.2
[✓] Android Studio (version 2024.1)
• Android Studio at /Applications/Android Studio.app/Contents
• Flutter plugin can be installed from:
🔨 https://plugins.jetbrains.com/plugin/9212-flutter
• Dart plugin can be installed from:
🔨 https://plugins.jetbrains.com/plugin/6351-dart
• Java version OpenJDK Runtime Environment (build 17.0.11+0-17.0.11b1207.24-11852314)
[✓] VS Code (version 1.96.1)
• VS Code at /Applications/Visual Studio Code.app/Contents
• Flutter extension version 3.102.0
[✓] Connected device (3 available)
• iPhone 12 mini (mobile) • 00008101-0001510C3CF0001E • ios • iOS 18.1.1 22B91
• macOS (desktop) • macos • darwin-arm64 • macOS 15.1.1 24B91 darwin-arm64
• Mac Designed for iPad (desktop) • mac-designed-for-ipad • darwin • macOS 15.1.1 24B91 darwin-arm64
[✓] Network resources
• All expected network resources are available.
! Doctor found issues in 1 category.```
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Important issues not at the top of the work listIssues with https://api.flutter.dev/flutter/packages/flutter/material repository.Found to occur in 3.27Found to occur in 3.28flutter/packages/flutter repository. See also f: labels.For the attention of Framework teamThe issue has been confirmed reproducible and is ready to work onOwned by Engine team