Drawing a Rectangle of Size 2X2 Inches -Inches to Pixel Conversion

Question

I need to draw a rectangle that should be around the size 2X2 Inches when printed on a paper.

I know that i can draw a rectangle using

 g.DrawRectangle(pen, 100,100, 100, 200);

This application will only be used in computers.How can i convert the inches to pixels properly so that i can get the desired dimensions when printed.

Answer 1

To make an image print in the right size by default, it needs to have the right combination of dpi and pixels.

Let's look at an example:

// aiming at 150dpi and 4x6 inches:
float dpi = 150;
float width = 4;
float height = 6;

using (Bitmap bmp = new Bitmap((int)(dpi * width), (int)(dpi * height)))
{
    // first set the resolution
    bmp.SetResolution(dpi, dpi);
    // then create a suitable Graphics object:
    using (Graphics G = Graphics.FromImage(bmp))
    using (Pen pen = new Pen(Color.Orange))
    {
        pen.Alignment = System.Drawing.Drawing2D.PenAlignment.Center;
        G.Clear(Color.FloralWhite);
        // using pixels here:

        Size sz = new System.Drawing.Size((int)dpi * 2 - 1, (int)dpi * 2 - 1);
        G.DrawRectangle(pen, new Rectangle(new Point(0, 0), sz));
        G.DrawRectangle(pen, new Rectangle(new Point(0, 300), sz));
        G.DrawRectangle(pen, new Rectangle(new Point(0, 600), sz));
        G.DrawRectangle(pen, new Rectangle(new Point(300, 0), sz));
        G.DrawRectangle(pen, new Rectangle(new Point(300, 300), sz));
        G.DrawRectangle(pen, new Rectangle(new Point(300, 600), sz));

        // alternative code:
        // we can also set the Graphics object to measure stuff in inches;
        G.PageUnit = GraphicsUnit.Inch;
        // or fractions of it, let's use 10th:
        G.PageScale = 0.1f;
        using (Pen pen2 = new Pen(Color.MediumPurple, 1f / dpi * G.PageScale))
        {
            // draw one rectangle offset by an inch:
            G.DrawRectangle(pen2, 10f, 10f, 20f, 20f);
        }

        bmp.Save(@"D:\xxx.jpg", ImageFormat.Jpeg);
    }
}

Note that I had to subtract 1 pixel from the drawn size as DrawRectangle overdraws by 1 pixel!

Note that the coordinates I draw at depend on the resolution! Also note how the jpeg format creates a lot of smeared colors. Pngcreates crisper results, especially once you print text..

Also note how I had to scale down the PenWidth in the alternative code!