adding custom painter demo code

Author: TechieBlossom

CustomPainterDemo.dart

@@ -0,0 +1,76 @@
+import 'package:flutter/material.dart';
+
+Color mainBGColor = Color(0xFF652A78);
+Color redColor = Color(0xFFDE3C10);
+Color purpleColor = Color(0xFF8132AD);
+Color cyan = Color(0xFF99D5E5);
+Color orange = Color(0xFFE97A4D);
+
+class CustomPaintDemo extends StatelessWidget {
+  @override
+  Widget build(BuildContext context) {
+    return MaterialApp(
+      debugShowCheckedModeBanner: false,
+      home: Scaffold(
+        body: CustomPaint(
+          painter: MyCustomPainter(),
+          child: Container(
+            height: 500.0,
+          ),
+        ),
+      ),
+    );
+  }
+}
+
+class MyCustomPainter extends CustomPainter {
+  @override
+  void paint(Canvas canvas, Size size) {
+    Paint paint = Paint();
+
+    Path mainBGPath = Path();
+    mainBGPath.addRect(Rect.fromLTWH(0.0, 0.0, size.width, size.height));
+    paint.color = mainBGColor;
+    canvas.drawPath(mainBGPath, paint);
+
+    Path purplePath = Path();
+    purplePath.lineTo(size.width * .45, 0);
+    purplePath.quadraticBezierTo(size.width * .25, size.height * .3, 0, size.height * 0.55);
+    purplePath.close();
+    paint.color = purpleColor;
+    canvas.drawPath(purplePath, paint);
+
+    Path redPath = Path();
+    redPath.moveTo(size.width * 0.9 , 0.0);
+    redPath.quadraticBezierTo(size.width * .5, size.height * 0.1, 0, size.height * 0.85);
+    redPath.lineTo(0, size.height);
+    redPath.lineTo(size.width * 0.25, size.height);
+    redPath.quadraticBezierTo(size.width * .5, size.height * 0.7, size.width, size.height * 0.6);
+    redPath.lineTo(size.width, 0.0);
+    redPath.close();
+    paint.color = redColor;
+    canvas.drawPath(redPath, paint);
+    
+    Path orangePath = Path();
+    orangePath.moveTo(0, size.height * 0.75);
+    orangePath.quadraticBezierTo(size.width * .25, size.height * 0.85, size.width * .40, size.height);
+    orangePath.lineTo(0, size.height);
+    orangePath.close();
+    paint.color = orange;
+    canvas.drawPath(orangePath, paint);
+
+    Path trianglePath = Path();
+    trianglePath.lineTo(size.width *.25, 0);
+    trianglePath.lineTo(0, size.height * .25);
+    trianglePath.close();
+    paint.color = cyan;
+    canvas.drawPath(trianglePath, paint);
+
+  }
+
+  @override
+  bool shouldRepaint(CustomPainter oldDelegate) {
+    return oldDelegate != this;
+  }
+
+}