how can I convert pixel measurement according to computer's DPI

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Hi,

I've published my wpf project to several users.
In my project - a user can place the mouse on a canvas and I save the exact point in pixels(x, y) in my database.

I've noticed that after a user that saved several points through his computer (which set to 113DPI), when I tried to see his points it were in a completely different places (my computer is set to 96DPI which is the standard as far a I know).

can you suggest a way, a calculation to change all the points he saved so it will fit the rest of the computers?

for example
name position_X position_Y
point_001 2505 1749

I hope that you'll understand what I mean.

thanx.

Posted 20-Jul-14 0:42am

danait25

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Richard MacCutchan 20-Jul-14 7:21am

You need to do a transform, by converting the points from their original values to the same relative positions on the new scale.

danait25 20-Jul-14 7:35am

Well that's what I'm trying to do- is there an equation for that?
How do I know where is the x position: 2505 pxl in 96dpi?

Richard MacCutchan 20-Jul-14 8:07am

It depends whether your position is relative to the screen (absolute co-ordinate) or to the Window of your application. In either case the formula is simply divide by the DPI of the screen that it is on and multiply by 96.

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CPallini · Answer 1 · 2014-07-20T02:39:00

Solution 1

The formula is simple:

target_x = source_x * target_dpi / source_dpi;
..

Posted 20-Jul-14 2:39am

CPallini

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danait25 21-Jul-14 3:23am

thanks. I tried that ofcourse but from some reason it's not working good.
I'll try again, maybe I did something wrong.

CPallini 21-Jul-14 3:26am

Could you please give us some details?