Choosr points and draw

Question

I want to pick points on the picture. These points converge into a recta.

Later i will use this rectange for picture cropping....

Firstly how can I draw this recta.?

Answer 1

Hi PaulDares-7770,
You can use Graphics.DrawRectangle method to draw a rectangle in pictureBox paint event.
Here is my test code you can refer to.

private Point clickLast = Point.Empty;  
private Point clickPrev = Point.Empty;  
private void pictureBox1_MouseDown(object sender, MouseEventArgs e)  
{  
    clickPrev = clickLast;  
    clickLast = new Point(e.X,e.Y);  
    if (clickPrev == Point.Empty) return;  
    pictureBox1.Refresh();  
     
}  
  
private void pictureBox1_Paint(object sender, PaintEventArgs e)  
{  
    int h = clickLast.Y - clickPrev.Y;  
    int w = clickLast.X - clickPrev.X;             
    System.Drawing.Pen pen = new System.Drawing.Pen(System.Drawing.Color.Red, 3);  
    e.Graphics.DrawRectangle(pen, clickPrev.X, clickPrev.Y, w, h);  
    clickLast = Point.Empty;  
}  

Test result:

Best Regards,
Daniel Zhang

---

If the response is helpful, please click "Accept Answer" and upvote it.

Note: Please follow the steps in our documentation to enable e-mail notifications if you want to receive the related email notification for this thread.

Answer 2

Just use the grafikmat.DrawRectangle() to draw your rectangle.

Not sure why you need to set width of matbmp to (bmp.Width / 4) and set cutimg.X to (bmp.Width / 2). You may want to verify that.

Answer 3

If you want to draw a Selection Rectangle, you can find samples in some archived threads , like for example :
draw selection rectangle (VB, ~same code in C#)
Drag Selection Box
Adding Drag/Drop/Resizable Selection Rectangle to Image Editor
etc...

and the old MSDN KB :
How to draw a rubber band rectangle or a focus rectangle in Visual C#