unit Unit1;

interface

uses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs, StdCtrls, ExtCtrls, Image32;

type
  TForm1 = class(TForm)
    Image1: TImage;
    Button1: TButton;
    procedure Button1Click(Sender: TObject);
  private
    { Private declarations }
  public
    { Public declarations }
  end;

var
  Form1: TForm1;

procedure AALine(x1,y1,x2,y2 : single; color: TColor32; Bitmap: TBitmap32);



implementation

{$R *.dfm}

procedure AALine(x1, y1, x2, y2: single; color: TColor32; Bitmap: TBitmap32);

    function CrossFadeColor(FromColor, ToColor: TColor32; Rate: Single) : TColor32;
    var
        R,G,B,A: BYTE;
    begin
//      r := Round(RedComponent(FromColor) * Rate + RedComponent(ToColor) * (1 - Rate));
//      g := Round(GreenComponent(FromColor) * Rate + GreenComponent(ToColor) * (1 - Rate));
//      b := Round(BlueComponent(FromColor) * Rate + BlueComponent(ToColor) * (1 - Rate));
//      a := Round(AlphaComponent(FromColor) * Rate + AlphaComponent(ToColor) * (1 - Rate));
        r := RedComponent(FromColor);
        g := GreenComponent(FromColor);
        b := BlueComponent(FromColor);
        a := Round(AlphaComponent(FromColor) * Rate);

      Result := RGBA(r,g,b,a); //RGB(b,g,r);
    end;

//    type
//      intarray = array[0..1] of integer;
//      pintarray = ^intarray;

procedure hpixel(x : single; y : integer);
var
  FadeRate : single;
begin
  FadeRate := x - trunc(x);
  with bitmap do
  begin
    if (x>=0) and (y>=0) and (height>y) and (width>x) then
          pColor32array(bitmap.ScanLine[y])[trunc(x)] := CrossFadeColor(Color,pColor32array(bitmap.ScanLine[y])[trunc(x)],1-FadeRate);

    if (trunc(x)+1>=0) and (y>=0) and (height>y) and (width>trunc(x)+1) then
          pColor32array(bitmap.ScanLine[y])[trunc(x)+1]:=CrossFadeColor(Color,pColor32array(bitmap.ScanLine[y])[trunc(x)+1],FadeRate);
  end;
end;

procedure vpixel(x : integer; y : single);
var
  FadeRate : single;
begin
  FadeRate:=y-trunc(y);
  with bitmap do
  begin
    if (x>=0) and (trunc(y)>=0) and (height>trunc(y)) and (width>x) then
                        pColor32array(bitmap.ScanLine[trunc(y)])[x]:=CrossFadeColor(Color,pColor32array(bitmap.ScanLine[trunc(y)])[x],1-FadeRate);

         if (x>=0) and (trunc(y)+1>=0) and (height>trunc(y)+1) and (width>x) then
         pColor32array(bitmap.ScanLine[trunc(y)+1])[x]:=CrossFadeColor(Color,pColor32array(bitmap.ScanLine[trunc(y)+1])[x],FadeRate);
         end;
end;

var i: integer;
    ly, lx, currentx, currenty, deltax, deltay, l, skipl: single;
begin
  if (x1 <> x2) or (y1 <> y2) then
  begin
//    bitmap.PixelFormat := pf32Bit;
//    Bitmap.Clear($00000000);

    currentx := x1;
    currenty := y1;
    lx := abs(x2 - x1);
    ly := abs(y2 - y1);

    if lx > ly then
    begin
      l := trunc(lx);
      deltay := (y2-y1)/l;
      if x1 > x2 then
      begin
        deltax := -1;
        skipl  := (currentx - trunc(currentx));
      end
      else
      begin
        deltax := 1;
        skipl  := 1- (currentx - trunc(currentx));
      end;
    end
    else
    begin
      l      :=  trunc(ly);
      deltax := (x2-x1)/l;
      if y1 > y2 then
      begin
        deltay := -1;
        skipl := (currenty-trunc(currenty));
      end
      else
      begin
        deltay := 1;
        skipl  := 1-(currenty-trunc(currenty));
      end;
    end;

    currentx := currentx+deltax*skipl;
    currenty := currenty+deltay*skipl;{}

    for i := 1 to trunc(l) do
    begin
      if lx > ly then
        vpixel(trunc(currentx), currenty)
      else
        hpixel(currentx, trunc(currenty));
        
      currentx := currentx + deltax;
      currenty := currenty + deltay;
    end;
end;
end;

procedure TForm1.Button1Click(Sender: TObject);
var
    bitmap: TBitmap32;
begin
    Bitmap := TBitmap32.Create;
    Bitmap.Width := 400;
    Bitmap.Height := 400;

    Image1.picture.Bitmap.Width := 400;
    Image1.picture.Bitmap.Height := 400;

    AALine(0,0, 300,100, $FFFF0000, Bitmap);
    Bitmap.DrawTo(0,0,Image1.Picture.Bitmap);


    Bitmap.Free;
end;

end.

影音风暴开源项目：guliverkli
里面Subtitles有实现字幕描边，阴影代码(我觉得性能还是很好的啦）



附件里有摘录的部分代码,是关于实现字幕的（C++）

字幕编辑器（Subresync）：字体输出效果