Convert a Rectangle into a RectangleF and vice versa in C#


The RectangleF structure has an overloaded assignment operator = that lets you simply set a RectangleF equal to a Rectangle, so converting a Rectangle into a RectangleF is easy.

That makes sense because converting from Rectangle to RectangleF is a widening conversion. The integer values that define a Rectangle can be placed within float values without losing any precision.

Converting a RectangleF to a Rectangle is only slightly harder. The RectangleF class provides two methods, Round and Truncate, that perform this conversion.

This is a narrowing conversion because the float values that define the RectangleF don’t necessarily fit in the Rectangle structure’s integer properties.

This example uses the following code to convert a Rectangle into a RectangleF and back, and draw to all three rectangles.

private void Form1_Paint(object sender, PaintEventArgs e)
    // Make a rectangle.
    Rectangle rect1 = new Rectangle(20, 20,
        this.ClientSize.Width - 40,
        this.ClientSize.Height - 40);

    // Convert to RectangleF.
    RectangleF rectf = rect1;

    // Convert back to Rectangle.
    Rectangle rect2 = Rectangle.Round(rectf);
    //Rectangle rect2 = Rectangle.Truncate(rectf);

    // Draw them.
    using (Pen the_pen = new Pen(Color.Red, 20))
        e.Graphics.DrawRectangle(the_pen, rect1);

        the_pen.Color = Color.Lime;
            rectf.X, rectf.Y, rectf.Width, rectf.Height);

        the_pen.Color = Color.Blue;
        the_pen.Width = 1;
        e.Graphics.DrawRectangle(the_pen, rect2);

The code first defines a Rectangle. It uses assignment to convert it into a RectangleF and then uses the RectangleF structure’s Round method to convert it back into a Rectangle. The program then draws all three rectangles on top of each other with different line widths and colors so you can see them all.

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