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var
  TempPic: TPicture;

// ...

procedure LoadPic(Pfad: String);
begin
  TempPic := TPicture.Create;
  TempPic.LoadFromFile(Pfad);

  Image1.Picture := TempPic;

  TempPic.Free;                    

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with TJPEGImage(ImagePlus1.Picture.Graphic) do
    begin
      PixelFormat := TJPEGPixelFormat(jf24Bit);  //oder jf8Bit
      //...
    end;                    

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image1.ControlStyle:=image1.ControlStyle+[csOpaque]; 
//oder 
image1.parent.ControlStyle:=image1.parent.ControlStyle+[csOpaque];                    

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...
var
  lCounter: integer
begin
  for lCounter:= 0 to ComponentCount-1 do begin
    if Components[lCounter].InheritsFrom(TWinControl) then begin
      TWinControl(Components[lCounter]).DoubleBuffered:= true;
    end;
  end;
end;                    

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 ImagePlusX.Picture.LoadFromFile(OpenPictureDialog1.Files[B]);
 TImagePlus(FindComponent('ImagePlus'+IntToStr(B))).
  Canvas.StretchDraw(Rect(0, 0, 69, 69),ImagePlusX.Picture.Graphic);                    

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procedure ProportionalPicture(Image, DestImage: TImage;
 SourceWidth, SourceHeight, DestWidth, DestHeight: Integer; HGColor: TColor);
var
  I, L, T, Xnew, Ynew, H, W: Integer;
begin
 with DestImage do
 begin
  Picture.Graphic := nil;
  Canvas.Brush.Color := HGColor;
  Canvas.FillRect(Rect(0, 0, Width, Height));
 end;

 Xnew := (SourceWidth * DestWidth) div SourceHeight;
 Ynew := (DestHeight * SourceHeight) div SourceWidth;

 L := 0;
 T := 0;
 for I := Xnew to DestWidth do Inc(L);
 for I := Ynew to DestHeight do Inc(T);

 W := DestWidth div 3;
 H := DestHeight div 3;

 if Xnew > Ynew then
  DestImage.
   Canvas.StretchDraw(Rect(L div 2, T div 2, Xnew-W, Ynew+T div 2),Image.Picture.Graphic)
 else if Xnew < Ynew then
  DestImage.
   Canvas.StretchDraw(Rect(L div 2, T div 2, Xnew+L div 2, Ynew-H),Image.Picture.Graphic)
 else if Xnew = Ynew then
  DestImage.Canvas.StretchDraw(Rect(L, T, Xnew, Ynew),Image.Picture.Graphic);
end;                    

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 ImageX.Picture.LoadFromFile(//FileName
 ProportionalPicture(ImageX, Image1, ImageX.Picture.Width, ImageX.Picture.Height, 69, 69, clBtnFace)                    

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procedure TForm1.Button1Click(Sender: TObject);
var
  NewWidth, NewHeight, OffsetX, OffsetY: Integer;
begin
  with Image1.Picture.Bitmap do begin
    // Größe setzen und Hintergrund löschen
    Width := 200;
    Height := 200;

    Canvas.Brush.Color := clBtnFace;
    Canvas.FillRect(Canvas.ClipRect);

    // neue Bildgröße berechnen
    NewWidth := 200;
    NewHeight := 200;

    if Image2.Picture.Width > Image2.Picture.Height
      then NewHeight := 200 * Image2.Picture.Height div Image2.Picture.Width
      else NewWidth := 200 * Image2.Picture.Width div Image2.Picture.Height;

    // Bild Zentriert darstellen
    OffsetX := (Width - NewWidth) div 2;
    OffsetY := (Height - NewHeight) div 2;

    Canvas.StretchDraw(
      Rect(OffsetX, OffsetY, OffsetX + NewWidth, OffsetY + NewHeight),
      Image2.Picture.Graphic);
  end;
end;                    

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 with Image1.Picture.Bitmap do begin                    

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 with Image1.Picture.Graphic do begin