Question

I a have a PictureBox with a picture in a Windows Form application in C# language.I want draw a FillRectangle in some location of picturebox.but i also need to see picture of picture box.how can i draw this rectangle with low opacity to see image of picturebox?

Answer 1

Do you mean:

using (Graphics g = Graphics.FromImage(pb.Image))
{
    using(Brush brush = new SolidBrush(your_color))
    {
        g.FillRectangle(brush, x, y, width, height);
    }
}

or you can use

Brush brush = new SolidBrush(Color.FromArgb(alpha, red, green, blue))

where alpha goes from 0 to 255, so a value of 128 for your alpha will give you 50%
opactity.