如何在颤动中将图像添加到任何形状？

Question

我是 flutter 的新手，遇到了在 flutter 中向形状添加图像的问题。我已经创建了自定义形状，但无法将图像插入其中。这是我想要实现的目标： A picture inside a custom shape

我尝试将 Image 作为 CustomPainter 的子级，但仍然没有很好的结果。

任何人都可以提出一个好的方法吗？

Answer 1

正如 Midhun MP 提到的，用 ClipPath

包裹你的图像

  @override
  Widget build(BuildContext context) {
    return ClipPath(
      child: image,
      clipper: AnyClipper(),
    );
  }

并使用CustomClipper

class AnyClipper extends CustomClipper<Path> {
  @override
  Path getClip(Size size) {
    var path = Path();
    //... do something
    return path;
  }

  @override
  bool shouldReclip(CustomClipper<Path> oldClipper) => false;
}

Answer 2

如 Mindhun MP 所写，您需要使用自定义剪辑器。下面是裁剪容器的示例：

ClipPath(
      clipper: _CustomClipper(),
      child: Container(...),
);

你的情况应该与我的类似，所以请查看 quadraticBezierTo 函数。我的例子：

class _CustomClipper extends CustomClipper<Path> {
  @override
  Path getClip(Size size) {
    final double heightDelta = size.height / 2.2;

    return Path()
      ..addRect(
          Rect.fromLTWH(0, heightDelta, size.width, size.height - heightDelta))
      ..moveTo(0, heightDelta)
      ..quadraticBezierTo(
        size.width / 2,
        heightDelta - size.width / 2,
        size.width,
        heightDelta,
      );
  }

  @override
  bool shouldReclip(CustomClipper<Path> oldClipper) => true;
}

此外，here 是一篇很棒的文章，它详细解释了 Flutter 中的路径。

Answer 3

使用 CustomPaint，您可以将图像用作覆盖原始图像的蒙版，并仅显示蒙版中包含的图像内容。在那种情况下是一个形状。在下面的代码中 shape.png 就像掩码一样，只是 png 文件中不透明的部分将显示 [=18= 中的内容]。因此，您需要创建一个具有所需形状的 png 文件，并将其作为叠加层应用到图像上。

import 'dart:typed_data';
import 'dart:ui' as ui;

import 'package:flutter/cupertino.dart';
import 'package:flutter/material.dart';
import 'package:flutter/services.dart' show rootBundle;


class MaskedImageWithPainter extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: MyHomePage(title: 'Flutter Demo Home Page'),
    );
  }
}

class MyHomePage extends StatefulWidget {
  MyHomePage({Key key, this.title}) : super(key: key);

  final String title;

  @override
  _MyHomePageState createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  ui.Image mask;
  ui.Image image;

  @override
  void initState() {
    super.initState();
    load('assets/shape.png').then((i) {
      setState(() {
        mask = i;
      });
    });
    load('assets/image.jpeg').then((i) {
      setState(() {
        image = i;
      });
    });
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(backgroundColor: Colors.blue, title: Text('I am a title')),
      body: SafeArea(
        child: SizedBox(
          width: 200.0,
          height: 200.0,
          child: CustomPaint(painter: OverlayPainter(mask, image)),
        ),
      ),
    );
  }

  Future<ui.Image> load(String asset) async {
    ByteData data = await rootBundle.load(asset);
    ui.Codec codec = await ui.instantiateImageCodec(data.buffer.asUint8List());
    ui.FrameInfo fi = await codec.getNextFrame();
    return fi.image;
  }
}

class OverlayPainter extends CustomPainter {
  ui.Image mask;
  ui.Image image;

  OverlayPainter(this.mask, this.image);

  @override
  void paint(Canvas canvas, Size size) {
    if (image != null && mask != null) {
      var rect = Rect.fromLTRB(0, 0, 200, 200);
      Size outputSize = rect.size;
      Paint paint = new Paint();

      //Mask
      Size maskInputSize = Size(mask.width.toDouble(), mask.height.toDouble());
      final FittedSizes maskFittedSizes =
          applyBoxFit(BoxFit.cover, maskInputSize, outputSize);
      final Size maskSourceSize = maskFittedSizes.source;

      final Rect maskSourceRect = Alignment.center
          .inscribe(maskSourceSize, Offset.zero & maskInputSize);

      canvas.saveLayer(rect, paint);
      canvas.drawImageRect(mask, maskSourceRect, rect, paint);

      //Image
      Size inputSize = Size(image.width.toDouble(), image.height.toDouble());
      final FittedSizes fittedSizes =
          applyBoxFit(BoxFit.cover, inputSize, outputSize);
      final Size sourceSize = fittedSizes.source;
      final Rect sourceRect =
          Alignment.center.inscribe(sourceSize, Offset.zero & inputSize);

      canvas.drawImageRect(
          image, sourceRect, rect, paint..blendMode = BlendMode.srcIn);
      canvas.restore();
    }
  }

  @override
  bool shouldRepaint(OverlayPainter oldDelegate) {
    return mask != oldDelegate.mask || image != oldDelegate.image;
  }
}

如何在颤动中将图像添加到任何形状？

How to add images to any shapes in flutter?

flutter

dart

flutter-layout

flutter-web

dart-webui