Android Question Calculate number of pixels = 3cm

udg said:

Hi,
in my dgBarCode lib I had the goal to precisely respect the dimensions set by symbology standards. So I made use of the following routines:

B4X:

'converts dots-per-inch into dots-per-millimeter
Private Sub dpi2dpmm(val As Float) As Float
  Return (val / 25.4)
End Sub

'returns Display metrics in inches or millimeters
Private Sub getDisplayMetrics(Xaxis As Boolean, UnitInches As Boolean) As Float
  Dim xdpi, ydpi As Float
  Dim r As Reflector
  r.Target = r.GetContext
  r.Target = r.RunMethod("getResources")
  r.Target = r.RunMethod("getDisplayMetrics")
  xdpi=r.GetField("xdpi")  'is xdpi an int or a float?
  ydpi=r.GetField("ydpi")
   If Xaxis Then
    If UnitInches Then Return xdpi Else Return dpi2dpmm(xdpi)
   Else
    If UnitInches Then Return ydpi Else Return dpi2dpmm(ydpi)
   End If
End Sub

You use it like this:
w = 0.33 * getDisplayMetrics(True,False) 'width 0.33 mm

In my case it worked well. Try it.

udg

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