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How to get pixels per millimeter for current screen? [message #36037]

Fri, 20 April 2012 11:47

slashupp
Messages: 231
Registered: July 2009

Experienced Member

I'm implementing some WYSIWYG functionality and need to calculate
sizes specified in mm to the correct on-screen representation in
pixels.

Where/how do I get the pixel-to-mm ratio?

[edit]
I'm trying:

void checkresolution::Paint(Draw &w)
{
Size szpmm = w.GetPageMMs();
Size szpp = w.GetPagePixels();

double ppmmx = (double)szpp.cx/(double)szpmm.cx;
double ppmmy = (double)szpp.cy/(double)szpmm.cy;
//double dppmm = (ppmmx + ppmmy)/2;

//int ppmm = (int)(dppmm + 0.5);
int ppmm = (int)(ppmmx + 0.5);

int cm3 = (int)(ppmm * 30.0);
int cm7 = (int)(ppmm * 70.0);

w.DrawLine(10,10,cm3,10,3,Black());
w.DrawLine(10,15,cm7,15,3,Black());

}

The value I get is not quite correct, but seems that this is
the best I can hope for? The error occurs with the rounding
from double to int that Draw requires.

[Updated on: Sat, 21 April 2012 08:15]

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