Drawing Custom Shapes With CustomPainter in Flutter: Как использовать CustomPainter в Flutter для рисования кастомных фигур и контуров.
https://www.raywenderlich.com/7560981-drawing-custom-shapes-with-custompainter-in-flutter
https://www.raywenderlich.com/7560981-drawing-custom-shapes-with-custompainter-in-flutter