books

assets/draw/p07/s04.dart

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+import 'dart:async';
+import 'dart:ui' as ui;
+import 'package:flutter/material.dart';
+import 'package:flutter/services.dart';
+
+import '../components/coordinate_pro.dart';
+
+
+/// create by 张风捷特烈 on 2020-03-19
+/// contact me by email 1981462002@qq.com
+/// 说明: 纸
+
+class Paper extends StatefulWidget {
+  const Paper({super.key});
+
+  @override
+  _PaperState createState() => _PaperState();
+}
+
+class _PaperState extends State<Paper> {
+  ui.Image? _srcImage;
+  ui.Image? _dstImage;
+
+  @override
+  void initState() {
+    super.initState();
+    _loadImage();
+  }
+
+  void _loadImage() async {
+    _srcImage = await loadImageFromAssets('assets/images/src.png');
+    _dstImage = await loadImageFromAssets('assets/images/dst.png');
+    setState(() {});
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    return Container(
+        color: Colors.white,
+        child: CustomPaint(painter: PaperPainter(_srcImage, _dstImage)));
+  }
+
+  //读取 assets 中的图片
+  Future<ui.Image>? loadImageFromAssets(String path) async {
+    ByteData data = await rootBundle.load(path);
+    return decodeImageFromList(data.buffer.asUint8List());
+  }
+
+}
+
+class PaperPainter extends CustomPainter {
+  final ui.Image? srcImage;
+  final ui.Image? dstImage;
+
+  PaperPainter(this.srcImage, this.dstImage);
+
+  static const double step = 20; // 方格变长
+  final Coordinate coordinate = Coordinate(step: step);
+
+
+  @override
+  void paint(Canvas canvas, Size size) {
+    if (dstImage == null || srcImage == null) return;
+
+    Paint srcPaint = Paint();
+    Paint dstPaint = Paint();
+
+    int index = 4;
+
+    BlendMode srcModel = BlendMode.dstOver;
+    BlendMode dstModel = BlendMode.srcOver;
+
+    srcPaint
+      ..blendMode = srcModel;
+    dstPaint
+      ..blendMode = dstModel;
+
+    _simpleDrawText(canvas, BlendMode.values[index].toString().split(".")[1],
+        fontSize: 16,
+        offset: Offset(50, 50));
+
+    canvas.translate(size.width / 2, size.height / 2);
+
+    canvas.drawImageRect(
+        dstImage!,
+        Rect.fromPoints(
+            Offset.zero, Offset(dstImage!.width * 1.0, dstImage!.height * 1.0)),
+        Rect.fromCenter(
+            center: Offset.zero, width: 400, height: 400),
+        dstPaint);
+
+    canvas.drawImageRect(
+        srcImage!,
+        Rect.fromPoints(
+            Offset.zero, Offset(srcImage!.width * 1.0, srcImage!.height * 1.0)),
+        Rect.fromCenter(
+            center: Offset.zero, width: 400, height: 400),
+        srcPaint);
+
+  }
+
+  @override
+  bool shouldRepaint(CustomPainter oldDelegate) => true;
+
+  void _simpleDrawText(Canvas canvas, String str,
+      {double fontSize = 11,Offset offset = Offset.zero, Color color = Colors.black}) {
+    var builder = ui.ParagraphBuilder(ui.ParagraphStyle(
+      textAlign: TextAlign.left,
+      fontSize: fontSize,
+      textDirection: TextDirection.ltr,
+      maxLines: 1,
+    ))
+      ..pushStyle(
+        ui.TextStyle(color: color, textBaseline: ui.TextBaseline.alphabetic),
+      )
+      ..addText(str);
+
+    canvas.drawParagraph(
+        builder.build()
+          ..layout(ui.ParagraphConstraints(width: fontSize * str.length)),
+        offset);
+  }
+}