How to implement custom painting in Flutter?

Custom painting in Flutter:\n\n**CustomPainter Class:**\n\nclass MyPainter extends CustomPainter {\n @override\n void paint(Canvas canvas, Size size) {\n final paint = Paint()\n ..color = Colors.blue\n ..strokeWidth = 2.0\n ..style = PaintingStyle.stroke;\n \n // Draw circle\n canvas.drawCircle(\n Offset(size.width / 2, size.height / 2),\n 50.0,\n paint\n );\n \n // Draw path\n final path = Path()\n ..moveTo(0, size.height / 2)\n ..quadraticBezierTo(\n size.width / 2, 0,\n size.width, size.height / 2\n );\n canvas.drawPath(path, paint);\n }\n \n @override\n bool shouldRepaint(CustomPainter oldDelegate) => false;\n}\n\n\n**Usage:**\n\nCustomPaint(\n size: Size(200, 200),\n painter: MyPainter()\n)\n\n\n**Advanced Techniques:**\n• Clipping with clipPath()\n• Gradients and shaders\n• Image drawing\n• Text rendering\n• Transformations (rotate, scale, translate)\n\n**Performance Tips:**\n• Use shouldRepaint() wisely\n• Cache expensive calculations\n• Use RepaintBoundary for isolation\n• Minimize paint operations