[Solved] same example but it gives different values
lazarus / 39-Graphics

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barakli · 2014-08-06 20:27

i have two same examples. But two examples have different gray scale
image. why it is different?

first example code is:
Code: [Select]procedure TForm1.Button1Click(Sender: TObject);
var
  IntfImg1, IntfImg2: TLazIntfImage;
  px, py: Integer;
  Row1, Row2: PRGBTripleArray;
  abitmap:TBitmap;
begin
  abitmap:=TBitmap.Create;
  abitmap.LoadFromFile('bb.bmp');
  IntfImg1:=abitmap.CreateIntfImage;
  IntfImg2:=TLazIntfImage.Create(0,0);
  IntfImg2.LoadFromBitmap(aBitmap.Handle,aBitmap.MaskHandle);

   for py:=0 to IntfImg1.Height-1 do begin
     Row1 := IntfImg1.GetDataLineStart(py); //like Delphi
TBitMap.ScanLine
     Row2 := IntfImg2.GetDataLineStart(py); //like Delphi
TBitMap.ScanLine
     for px:=0 to IntfImg1.Width-1 do begin
       Row2^[px].rgbtRed    := 
round((Row1^[px].rgbtRed+Row1^[px].rgbtGreen+Row1^[px].rgbtBlue)/3);
       Row2^[px].rgbtGreen  := 
round((Row1^[px].rgbtRed+Row1^[px].rgbtGreen+Row1^[px].rgbtBlue)/3);
       Row2^[px].rgbtBlue   := 
round((Row1^[px].rgbtRed+Row1^[px].rgbtGreen+Row1^[px].rgbtBlue)/3);
     end;
   end;

   Image1.Stretch:=True;
   Image1.Picture.Bitmap.LoadFromIntfImage(IntfImg2);
end;

second code is:
Code: [Select]procedure TForm1.Button2Click(Sender: TObject);
  var
  IntfImg1, IntfImg2: TLazIntfImage;
  px, py: Integer;
  Row1, Row2: PRGBTripleArray;
  abitmap:TBitmap;
  CurColor: TFPColor;
begin
   abitmap:=TBitmap.Create;
   abitmap.LoadFromFile('bb.bmp');
   IntfImg1:=abitmap.CreateIntfImage;
   IntfImg2:=TLazIntfImage.Create(0,0);
   IntfImg2.LoadFromBitmap(aBitmap.Handle,aBitmap.MaskHandle);

    for py:=0 to IntfImg1.Height-1 do begin
      Row1 := IntfImg1.GetDataLineStart(py); //like Delphi
TBitMap.ScanLine
      Row2 := IntfImg2.GetDataLineStart(py); //like Delphi
TBitMap.ScanLine
      for px:=0 to IntfImg1.Width-1 do begin
        CurColor:=IntfImg1.Colors[px,py];
        CurColor.red    := 
round((CurColor.red+CurColor.green+CurColor.blue)/3);
        CurColor.green  := 
round((CurColor.red+CurColor.green+CurColor.blue)/3);
        CurColor.blue   := 
round((CurColor.red+CurColor.green+CurColor.blue)/3);
        IntfImg2.Colors[px,py]:=CurColor;
      end;
    end;

    Image1.Stretch:=True;
    Image1.Picture.Bitmap.LoadFromIntfImage(IntfImg2);
end;

first example result:       http://www.opencvtr.net/buglikod/1.png
second example result:  http://www.opencvtr.net/buglikod/2.png

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engkin · 2014-08-06 21:21

Welcome to FPC/Lazarus.

This mistake should teach you two things:
1-Do not repeat the same calculation.
2-Repeating the same calculations is wrong. The second case:
Quote        CurColor:=IntfImg1.Colors[px,py];
        CurColor.red    := 
round((CurColor.red+CurColor.green+CurColor.blue)/3);
        CurColor.green  := 
round((CurColor.red+CurColor.green+CurColor.blue)/3);
        CurColor.blue   := 
round((CurColor.red+CurColor.green+CurColor.blue)/3);
Legend:
Original value, New Value.

Do you see the mistake?

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Graeme · 2014-08-06 22:17

Quote from: engkin on August 06, 2014, 11:21:57 pmDo you see the
mistake?
At least the second one makes for a nice "sepia effect"

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engkin · 2014-08-07 02:56

Quote from: Graeme Geldenhuys on August 07, 2014, 12:17:29 amAt least
the second one makes for a nice "sepia effect"
That's true, it is nice.

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barakli · 2014-08-07 18:22

Thank you very much to engkin  and  i love this mistake. in God, I've
done this error.