Rotirea unei linii C#

De curand am rezolvat o problema care imi cerea sa rotesc o linie in jurul unui punct (subiectul de la C.I.A 2009 daca va mai aduceti aminte). Spre surprinderea mea rezolvarea problemei era foarte simpla fiind aplicata doar doua functii matematice Sinus si Cosinus cu care am calculat coordonatele punctelor.

public partial class Rotate : Form
    {
        public Bitmap image;
        public Graphics gra;

        public int angle = 10;
        public int step = 0;
        public int radius = 150;

        public System.Timers.Timer timer;

        public Rotate()
        {
            InitializeComponent();

            image = new Bitmap(400, 300);
            gra = Graphics.FromImage(image);

            gra.Clear(Color.DarkBlue);
            pictureBox1.Image = image;
        }

        private void button1_Click(object sender, EventArgs e)
        {
            if (timer == null)
            {
                timer = new System.Timers.Timer(50);
                timer.Elapsed += new ElapsedEventHandler(timer_Elapsed);

                timer.Start();
            }
        }

        private void button2_Click(object sender, EventArgs e)
        {
            if (timer != null)
            {
                timer.Stop();
                timer = null;
            }
        }

        void timer_Elapsed(object sender, ElapsedEventArgs e)
        {
            gra.Clear(Color.DarkBlue);

            PointF point1 = new PointF(200, 150);
            PointF point2 = new PointF();

            point2.X = radius * (float)Math.Cos(DegreesToRadians(angle * step)) + 200;
            point2.Y = radius * (float)Math.Sin(DegreesToRadians(angle * step)) + 150;
            gra.DrawLine(new Pen(Color.White), point1, point2);
            step++;

            pictureBox1.Image = image;
        }

        private double DegreesToRadians(double angle)
        {
            return angle * Math.PI / 180.0;
        }
    }

Explicarea codului:

        public Bitmap image;
        public Graphics gra;

        public int angle = 10;
        public int step = 0;
        public int radius = 150;

        public System.Timers.Timer timer;

       public Rotate()
        {
           InitializeComponent();
           image = new Bitmap(400, 300)
           gra = Graphics.FromImage(image);
           gra.Clear(Color.DarkBlue);
           pictureBox1.Image = image;
       }

Pentru inceput am initializat 2 variable angle si step care inmultite vor da unghiu cu care linia trebuie rotitata, un step de 36 va rezulta intr’o rotire completa a linii (10 * 36 = 360 grade), in constructorul clasei am initializat imaginea propriu zisa si am setat backgroundu la culoarea DarkBlue.

            gra.Clear(Color.DarkBlue);

            PointF point1 = new PointF(200, 150);
            PointF point2 = new PointF();

            point2.X = radius * (float)Math.Cos(DegreesToRadians(angle * step)) + 200;
            point2.Y = radius * (float)Math.Sin(DegreesToRadians(angle * step)) + 150;
            gra.DrawLine(new Pen(Color.White), point1, point2);
            step++;

Observam ca folosim functia DegreesToRadians pentru a asigura parametrul functiei sin/cos asta deoarce acesta ia valoare in radieni si nu in grade. Cifrele adaugate la sfarsit ( + 200/ 150 ) reprezinta ‘offsetu’ de la care a inceput primul punct, acestea fiind necesare pentru calcularea corecta a punctelor (obtinem niste efecte destul de interesante daca scoatem un offseturile :))

Puteti descarca proiectul complet aici.

Articol original Area72.

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