{The parameter "percent" needs an integer between 0 and 100
(include zero and 100). If "Percent" is 0, there will be no effect.
If it's 100 there will be the strongest effect.}

procedure Antialising(C: TCanvas; Rect: TRect; Percent: Integer);
var
 l, p: Integer;
 R, G, B: Integer;
 R1, R2, G1, G2, B1, B2: Byte;
begin
 with c do
 begin
 Brush.Style := bsclear;
 lineto(200, 100);
 moveto(50, 150);
 Ellipse(50, 150, 200, 30);
 for l := Rect.Top to Rect.Bottom do
 begin
 for p := Rect.Left to Rect.Right do
 begin
 R1 := GetRValue(Pixels[p, l]);
 G1 := GetGValue(Pixels[p, l]);
 B1 := GetBValue(Pixels[p, l]);

 //Pixel links
 //Pixel left
 R2 := GetRValue(Pixels[p - 1, l]);
 G2 := GetGValue(Pixels[p - 1, l]);
 B2 := GetBValue(Pixels[p - 1, l]);

 if (R1 <> R2) or (G1 <> G2) or (B1 <> B2) then
 begin
 R := Round(R1 + (R2 - R1) * 50 / (Percent + 50));
 G := Round(G1 + (G2 - G1) * 50 / (Percent + 50));
 B := Round(B1 + (B2 - B1) * 50 / (Percent + 50));
 Pixels[p - 1, l] := RGB(R, G, B);
 end;

 //Pixel rechts
 //Pixel right
 R2 := GetRValue(Pixels[p + 1, l]);
 G2 := GetGValue(Pixels[p + 1, l]);
 B2 := GetBValue(Pixels[p + 1, l]);

 if (R1 <> R2) or (G1 <> G2) or (B1 <> B2) then
 begin
 R := Round(R1 + (R2 - R1) * 50 / (Percent + 50));
 G := Round(G1 + (G2 - G1) * 50 / (Percent + 50));
 B := Round(B1 + (B2 - B1) * 50 / (Percent + 50));
 Pixels[p + 1, l] := RGB(R, G, B);
 end;

 //Pixel oben
 //Pixel up
 R2 := GetRValue(Pixels[p, l - 1]);
 G2 := GetGValue(Pixels[p, l - 1]);
 B2 := GetBValue(Pixels[p, l - 1]);

 if (R1 <> R2) or (G1 <> G2) or (B1 <> B2) then
 begin
 R := Round(R1 + (R2 - R1) * 50 / (Percent + 50));
 G := Round(G1 + (G2 - G1) * 50 / (Percent + 50));
 B := Round(B1 + (B2 - B1) * 50 / (Percent + 50));
 Pixels[p, l - 1] := RGB(R, G, B);
 end;

 //Pixel unten
 //Pixel down
 R2 := GetRValue(Pixels[p, l + 1]);
 G2 := GetGValue(Pixels[p, l + 1]);
 B2 := GetBValue(Pixels[p, l + 1]);

 if (R1 <> R2) or (G1 <> G2) or (B1 <> B2) then
 begin
 R := Round(R1 + (R2 - R1) * 50 / (Percent + 50));
 G := Round(G1 + (G2 - G1) * 50 / (Percent + 50));
 B := Round(B1 + (B2 - B1) * 50 / (Percent + 50));
 Pixels[p, l + 1] := RGB(R, G, B);
 end;
 end;
 end;
 end;
end;

procedure TForm1.Button1Click(Sender: TObject);
begin
 Antialising(Image1.Canvas, Image1.Canvas.ClipRect, 100);
end;