C#

Chesnokov Yuriy wrote:

Why the picture box update is very slow if I keep drawing on every mouse move event?

public partial class Form1 : Form
{
    bool drawRect = false;
    Rectangle r = new Rectangle();
    Brush br = new SolidBrush(Color.FromArgb(50, Color.Red));

    public Form1()
    {
        InitializeComponent();
    }

    private void pct_Paint(object sender, PaintEventArgs e)
    {
        if (drawRect)
            e.Graphics.FillRectangle(br, r);
    }

    private void pct_MouseDown(object sender, MouseEventArgs e)
    {
        drawRect = true;
        r.X = e.X;
        r.Y = e.Y;
    }

    private void pct_MouseMove(object sender, MouseEventArgs e)
    {
        r.Width = e.X - r.X;
        r.Height = e.Y - r.Y;

        Refresh();
    }

    private void pct_MouseUp(object sender, MouseEventArgs e)
    {
        drawRect = false;
        Refresh();
    }
}

...
roi_g.FillRectangle(new SolidBrush(Color.FromArgb(64, 0, 0, 0)), new Rectangle(0, 0, FrameWithRoi.Width, FrameWithRoi.Height));
roi_g.FillRectangle(new SolidBrush(Color.Red), rect);
region.MakeTransparent(Color.Red);
g.DrawImage(region, 0, 0);
...

private void pct_Paint(object sender, PaintEventArgs e)
{
    if (drawRect)
    {
        e.Graphics.FillRectangle(br, 0, 0, pct.Width, r.Y);
        e.Graphics.FillRectangle(br, 0, r.Y, r.X, pct.Height);
        e.Graphics.FillRectangle(br, r.X, r.Y + r.Height, pct.Width, pct.Height);
        e.Graphics.FillRectangle(br, r.X + r.Width, r.Y, pct.Width, r.Height);
    }
}

abstract class b
{
    public dynamic Create()
    {
        return Activator.CreateInstance(this.GetType());
    }
}

public virtual b Create() { return (b)Activator.CreateInstance(GetType()); }

void SomeFunction(b instance){
 b copy = instance.Create();
 instance.CopyTo(copy);
}

abstract class b
    {
                public virtual b Create() { return (b)Activator.CreateInstance(GetType()); }
    }

class Program
    {
        static void Main(string[] args)
        {
            D1 myClass = new D1();
            D1 newClass = myClass.Create();
            Console.WriteLine(newClass.KM);
            
            // Bur
            b myClassAb = new D1();
            b newClassAb = myClassAb.Create();
            Console.WriteLine(newClassAb.KM);//KM is not avaiable :(
        }
    }

b myClassAb = new D1();
         b newClassAb = myClassAb.Create();

class D1:b
  {
      ..
      public D1 Create() { return new D1(); }
  }
  class D2 : b
  {
      ..
      public D2 Create() { return new D2(); }
  }

abstract class b<T> where T: b, new()
{
    ...
    public T Create() { return new T(); }
}

class D1 : b<D1>
{
    ...
}
class D2 : b<D2>
{
    ...
}

D1 myClassD1 = new D1();
D1 newClassD1 = D1.Create();

b myClassAb = new D1;
D1 newClassAb = myClassAb.Create();

class b {
 private int someField;

 public b Copy() {
  b newB = Create();
  CopyTo(newB);
  return newB;
 }
 
 protected virtual void CopyTo(b newB){
  // copy properties into the target
  newB.someField = someField;
 }

class D1 : b {
 private double derivedField;

 protected override void CopyTo(b newD1){
  // This method will only be called if we are a D1,
  // and therefore the result of Create is also a D1,
  // and therefore the parameter is also a D1
  D1 target = (D1)newD1; // ... so this must succeed
  target.derivedField = derivedField; // ... and we can access D1's members
 }
}