Compute screen proportion

[freeway]

first part of your question, i realy don´t understand ???

work with fractions
http://en.wikipedia.org/wiki/Fraction_(mathematics)

[Furtbichler]

Do you know the difference between display resolution and aspect ratio? Why do you name your thread 'screen proportion' but you refer to images?
Did you bother using google?
I found all answers.

But what the heck:

Most modern screen resulutions are not exactly 16:9, 4:3 etc.

I would recommend using a list of standard ratios, e.g. (4:3, 5:4, 16:9, 16:10), compare the screen dimension (widht / height) with the entries in the list and return the closest candidate or 'none' if the difference is out of tolerance.

Delphi-Quellcode:

Function AspectRatio (aWidth, aHeight : Integer) : String;
Const
  RatioX : Array [0..3] of integer = (4,5,16,16);
  RatioY : Array [0..3] of integer = (3,4,10, 9);

  tolerance = 1E-2;

Var
  diff,dmin, ratio : Double;
  i,j : Integer;

Begin
  ratio := aWidht/aHeight;
  dmin := 999;
  j:=-1;
  for i:=0 to High(RatioX) do begin
    diff := abs(RatioX[i]/RatioY[i] - ratio);
    if diff < dmin then begin
      j := i;
      dmin := diff;
    end
  end;

  if diff<tolerance then
     result := Format('%d:%d',[RatioX[j], RatioY[j]])
  else
     result := 'nonstandard';
End;

[WojTec]

Thanks, but for eg. 1024x768 returns 'nonstandard'

[Furtbichler]

The code is untested.

What would you do go make it work?
Do you understand the Code?

[Amateurprofi]

This should work:

Delphi-Quellcode:

FUNCTION AspectRatio(width,height:Integer):String;
FUNCTION LCD(v1,v2:integer):integer;
begin
   result:=0;
   if (v1>0) and (v2>0) then begin
      repeat
         result:=v1 mod v2;
         v1:=v2;
         v2:=result;
      until v2=0;
      result:=v1;
   end;
end;
var divisor:integer; s:string;
begin
   divisor:=LCD(width,height);
   if divisor=0 then result:='Width or Height <= 0'
      else result:=IntToStr(width div divisor)+':'+IntToStr(height div divisor);
end;

[Furtbichler]

The GCD of 1366 x 768 is 2. However these displays are treated as 16:9.

[WojTec]

I modified @Amateurprofi code to support x:10, changed to return float and wrote format function:

Delphi-Quellcode:

function GetScreenProportion(const AWidth, AHeight: Cardinal): string;
var
  AspectRatio: Single;
  X, Y: Extended;
begin
  AspectRatio := GetScreenAspectRatio(AWidth, AHeight);
  X := Int(AspectRatio);
  Y := Frac(AspectRatio) * 100;

  if Int(Y) <> 10 then
    Y := Y / 10
  ;

  Result := Format('%.0f:%.0f', [X, Y])
end;

Thanks