How to get accurate metric from dpix/dpiy?

Question

0.00/5 (No votes)

See more:

I want to create a text box with accurate size by 5 inch by 7 inch.

I created a simple Windows Form app and two labels and one textBox.
here is the Form1_Load event handler:

private void Form1_Load(object sender, EventArgs e)
 {
     using (Graphics g=this.CreateGraphics())
     {
         label1.Text = g.DpiX.ToString();
         label2.Text = g.DpiY.ToString();

         //width:5 inch
         //height:7 inch
         //textBox1.Size =new Size( (int)Math.Ceiling(5 * g.DpiX), (int)Math.Ceiling(7*g.DpiY));
         int width = (int)(5 * g.DpiX);
         int height = (int)(7 * g.DpiY);

         textBox1.Size = new Size(width, height);

     }
 }

but when I use a physical ruler to measure this textbox, I find out its width is more than 5 inch and height is much larger than 7 inch.

is there anything wrong with my understanding with this DpiX and DpiY values of Graphics object?

What I have tried:

I searched internet and did not find the good answer.

Posted 25-May-22 14:48pm

Southmountain

Updated 25-May-22 19:01pm

Add a Solution

1 solution

Add a Solution

This content, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

OriginalGriff · Accepted Answer · 2022-05-25T19:01:00

DPI is not the same as resolution, and have nothing to do with the actual physical size of the monitor and everything to do with fonts.

The physical screen has two relevant sizes: Resolution, which is the actual number of pixels X and Y (which windows does know) and Size in cm or inches (which Windows may or may not know).
DPI is not related to either of those and the mapping to physical pixels is also affected by the Windows Zoom setting, which is a "global size changer".

As far as I know there is no reliable way to get the actual on-screen height or width in terms that the drawing system gat relate to without drawing a physical box on the screen and getting the user to actually measure it to give you an "adjustment factor" that works for the current monitor and the current monitor / adapter / Zoom settings - and even that may not work if the user drags the app to a second or third monitor!

Basically, you should assume that the user is comfortable with the text size he has picked and relate your app around "n lines of text" instead of trying to measure it in outside world terms as therein lies a world of pain.

How to get accurate metric from dpix/dpiy?

1 solution

Solution 1

Add your solution here

Preview 0

How to get accurate metric from dpix/dpiy?

1 solution

Solution 1

Add your solution here

Preview 0

Existing Members

...or Join us