Title: How to Convert Pixels to Millimeters (Delphi code)
If you need to convert pixel value to millimeters (inches, centimeters, etc.) use the code provided here.
The code uses the API function GetDeviceCaps to get the metrics you need.
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procedure PixelsPerMM(
canvas: TCanvas;
var x, y: single) ;
var
H:HDC;
hres,vres,
hsiz,vsiz:integer;
begin
H:=canvas.handle;
hres := GetDeviceCaps(H,HORZRES) ; {display width in pixels}
vres := GetDeviceCaps(H,VERTRES) ; {display height in pixels}
hsiz := GetDeviceCaps(H,HORZSIZE) ; {display width in mm}
vsiz := GetDeviceCaps(H,VERTSIZE) ; {display height in mm}
x := hres/hsiz;
y := vres/vsiz;
end;
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Now, to actually convert an amount of pixels, let's say 468, to milimeters, use the next steps:
1. First, call the conversion function only once to get the pixel per milimeter ration for the required device (Screen, Printer, ...)
2. Next, transform an amount of pixels to millimeteres, depending on the orientation (horizontal, vertical)
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var
cx, cy : single;
mmx, mmy : integer;
begin
PixelsPerInch(Handle,cx,cy) ;
mmx := Trunc(468 / PixelsInMM.y) ;
mmy := Trunc(60 / PixelsInMM.y) ;
end;
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